Commit 92deff7a authored by Lorenzo "Palinuro" Faletra's avatar Lorenzo "Palinuro" Faletra
Browse files

Import Upstream version 5.3.7

parent 407d19ab
......@@ -300,4 +300,4 @@ Description:
Using this sysfs file will override any values that were
set using the kernel command line for disk offset.
\ No newline at end of file
set using the kernel command line for disk offset.
......@@ -212,7 +212,7 @@ The standard 64-bit addressing device would do something like this::
If the device only supports 32-bit addressing for descriptors in the
coherent allocations, but supports full 64-bits for streaming mappings
it would look like this:
it would look like this::
if (dma_set_mask(dev, DMA_BIT_MASK(64))) {
dev_warn(dev, "mydev: No suitable DMA available\n");
......@@ -198,7 +198,7 @@ call to set the mask to the value returned.
dma_direct_max_mapping_size(struct device *dev);
dma_max_mapping_size(struct device *dev);
Returns the maximum size of a mapping for the device. The size parameter
of the mapping functions like dma_map_single(), dma_map_page() and
In the good old days when graphics parameters were configured explicitly
in a file called xorg.conf, even broken hardware could be managed.
Today, with the advent of Kernel Mode Setting, a graphics board is
either correctly working because all components follow the standards -
or the computer is unusable, because the screen remains dark after
booting or it displays the wrong area. Cases when this happens are:
- The graphics board does not recognize the monitor.
- The graphics board is unable to detect any EDID data.
- The graphics board incorrectly forwards EDID data to the driver.
- The monitor sends no or bogus EDID data.
- A KVM sends its own EDID data instead of querying the connected monitor.
Adding the kernel parameter "nomodeset" helps in most cases, but causes
restrictions later on.
As a remedy for such situations, the kernel configuration item
CONFIG_DRM_LOAD_EDID_FIRMWARE was introduced. It allows to provide an
individually prepared or corrected EDID data set in the /lib/firmware
directory from where it is loaded via the firmware interface. The code
(see drivers/gpu/drm/drm_edid_load.c) contains built-in data sets for
commonly used screen resolutions (800x600, 1024x768, 1280x1024, 1600x1200,
1680x1050, 1920x1080) as binary blobs, but the kernel source tree does
not contain code to create these data. In order to elucidate the origin
of the built-in binary EDID blobs and to facilitate the creation of
individual data for a specific misbehaving monitor, commented sources
and a Makefile environment are given here.
To create binary EDID and C source code files from the existing data
material, simply type "make".
If you want to create your own EDID file, copy the file 1024x768.S,
replace the settings with your own data and add a new target to the
Makefile. Please note that the EDID data structure expects the timing
values in a different way as compared to the standard X11 format.
HTimings: hdisp hsyncstart hsyncend htotal
VTimings: vdisp vsyncstart vsyncend vtotal
#define XPIX hdisp
#define XBLANK htotal-hdisp
#define XOFFSET hsyncstart-hdisp
#define XPULSE hsyncend-hsyncstart
#define YPIX vdisp
#define YBLANK vtotal-vdisp
#define YOFFSET vsyncstart-vdisp
#define YPULSE vsyncend-vsyncstart
bool "Warn if there's a missing documentation file"
depends on COMPILE_TEST
It is not uncommon that a document gets renamed.
This option makes the Kernel to check for missing dependencies,
warning when something is missing. Works only if the Kernel
is built from a git tree.
If unsure, select 'N'.
......@@ -4,6 +4,11 @@
subdir-y := devicetree/bindings/
# Check for broken documentation file references
$(shell $(srctree)/scripts/documentation-file-ref-check --warn)
# You can set these variables from the command line.
SPHINXBUILD = sphinx-build
......@@ -23,11 +28,13 @@ ifeq ($(HAVE_SPHINX),0)
$(warning The '$(SPHINXBUILD)' command was not found. Make sure you have Sphinx installed and in PATH, or set the SPHINXBUILD make variable to point to the full path of the '$(SPHINXBUILD)' executable.)
@echo " SKIP Sphinx $@ target."
export SPHINXOPTS = $(shell perl -e 'open IN,"sphinx-build --version 2>&1 |"; while (<IN>) { if (m/([\d\.]+)/) { print "-jauto" if ($$1 >= "1.7") } ;} close IN')
# User-friendly check for pdflatex and latexmk
HAVE_PDFLATEX := $(shell if which $(PDFLATEX) >/dev/null 2>&1; then echo 1; else echo 0; fi)
HAVE_LATEXMK := $(shell if which latexmk >/dev/null 2>&1; then echo 1; else echo 0; fi)
......@@ -70,12 +77,14 @@ quiet_cmd_sphinx = SPHINX $@ --> file://$(abspath $(BUILDDIR)/$3/$4)
$(abspath $(BUILDDIR)/$3/$4)
@$(srctree)/scripts/sphinx-pre-install --version-check
@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,html,$(var),,$(var)))
@$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,linkcheck,$(var),,$(var)))
@$(srctree)/scripts/sphinx-pre-install --version-check
@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,latex,$(var),latex,$(var)))
ifeq ($(HAVE_PDFLATEX),0)
......@@ -87,14 +96,17 @@ pdfdocs:
pdfdocs: latexdocs
@$(srctree)/scripts/sphinx-pre-install --version-check
$(foreach var,$(SPHINXDIRS), $(MAKE) PDFLATEX="$(PDFLATEX)" LATEXOPTS="$(LATEXOPTS)" -C $(BUILDDIR)/$(var)/latex || exit;)
@$(srctree)/scripts/sphinx-pre-install --version-check
@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,epub,$(var),epub,$(var)))
@$(srctree)/scripts/sphinx-pre-install --version-check
@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,xml,$(var),xml,$(var)))
The MSI Driver Guide HOWTO
Tom L Nguyen
Revised Feb 12, 2004 by Martine Silbermann
Revised Jun 25, 2004 by Tom L Nguyen
Revised Jul 9, 2008 by Matthew Wilcox <>
Copyright 2003, 2008 Intel Corporation
1. About this guide
This guide describes the basics of Message Signaled Interrupts (MSIs),
the advantages of using MSI over traditional interrupt mechanisms, how
to change your driver to use MSI or MSI-X and some basic diagnostics to
try if a device doesn't support MSIs.
2. What are MSIs?
A Message Signaled Interrupt is a write from the device to a special
address which causes an interrupt to be received by the CPU.
The MSI capability was first specified in PCI 2.2 and was later enhanced
in PCI 3.0 to allow each interrupt to be masked individually. The MSI-X
capability was also introduced with PCI 3.0. It supports more interrupts
per device than MSI and allows interrupts to be independently configured.
Devices may support both MSI and MSI-X, but only one can be enabled at
a time.
3. Why use MSIs?
There are three reasons why using MSIs can give an advantage over
traditional pin-based interrupts.
Pin-based PCI interrupts are often shared amongst several devices.
To support this, the kernel must call each interrupt handler associated
with an interrupt, which leads to reduced performance for the system as
a whole. MSIs are never shared, so this problem cannot arise.
When a device writes data to memory, then raises a pin-based interrupt,
it is possible that the interrupt may arrive before all the data has
arrived in memory (this becomes more likely with devices behind PCI-PCI
bridges). In order to ensure that all the data has arrived in memory,
the interrupt handler must read a register on the device which raised
the interrupt. PCI transaction ordering rules require that all the data
arrive in memory before the value may be returned from the register.
Using MSIs avoids this problem as the interrupt-generating write cannot
pass the data writes, so by the time the interrupt is raised, the driver
knows that all the data has arrived in memory.
PCI devices can only support a single pin-based interrupt per function.
Often drivers have to query the device to find out what event has
occurred, slowing down interrupt handling for the common case. With
MSIs, a device can support more interrupts, allowing each interrupt
to be specialised to a different purpose. One possible design gives
infrequent conditions (such as errors) their own interrupt which allows
the driver to handle the normal interrupt handling path more efficiently.
Other possible designs include giving one interrupt to each packet queue
in a network card or each port in a storage controller.
4. How to use MSIs
PCI devices are initialised to use pin-based interrupts. The device
driver has to set up the device to use MSI or MSI-X. Not all machines
support MSIs correctly, and for those machines, the APIs described below
will simply fail and the device will continue to use pin-based interrupts.
4.1 Include kernel support for MSIs
To support MSI or MSI-X, the kernel must be built with the CONFIG_PCI_MSI
option enabled. This option is only available on some architectures,
and it may depend on some other options also being set. For example,
on x86, you must also enable X86_UP_APIC or SMP in order to see the
4.2 Using MSI
Most of the hard work is done for the driver in the PCI layer. The driver
simply has to request that the PCI layer set up the MSI capability for this
To automatically use MSI or MSI-X interrupt vectors, use the following
int pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
unsigned int max_vecs, unsigned int flags);
which allocates up to max_vecs interrupt vectors for a PCI device. It
returns the number of vectors allocated or a negative error. If the device
has a requirements for a minimum number of vectors the driver can pass a
min_vecs argument set to this limit, and the PCI core will return -ENOSPC
if it can't meet the minimum number of vectors.
The flags argument is used to specify which type of interrupt can be used
by the device and the driver (PCI_IRQ_LEGACY, PCI_IRQ_MSI, PCI_IRQ_MSIX).
A convenient short-hand (PCI_IRQ_ALL_TYPES) is also available to ask for
any possible kind of interrupt. If the PCI_IRQ_AFFINITY flag is set,
pci_alloc_irq_vectors() will spread the interrupts around the available CPUs.
To get the Linux IRQ numbers passed to request_irq() and free_irq() and the
vectors, use the following function:
int pci_irq_vector(struct pci_dev *dev, unsigned int nr);
Any allocated resources should be freed before removing the device using
the following function:
void pci_free_irq_vectors(struct pci_dev *dev);
If a device supports both MSI-X and MSI capabilities, this API will use the
MSI-X facilities in preference to the MSI facilities. MSI-X supports any
number of interrupts between 1 and 2048. In contrast, MSI is restricted to
a maximum of 32 interrupts (and must be a power of two). In addition, the
MSI interrupt vectors must be allocated consecutively, so the system might
not be able to allocate as many vectors for MSI as it could for MSI-X. On
some platforms, MSI interrupts must all be targeted at the same set of CPUs
whereas MSI-X interrupts can all be targeted at different CPUs.
If a device supports neither MSI-X or MSI it will fall back to a single
legacy IRQ vector.
The typical usage of MSI or MSI-X interrupts is to allocate as many vectors
as possible, likely up to the limit supported by the device. If nvec is
larger than the number supported by the device it will automatically be
capped to the supported limit, so there is no need to query the number of
vectors supported beforehand:
nvec = pci_alloc_irq_vectors(pdev, 1, nvec, PCI_IRQ_ALL_TYPES)
if (nvec < 0)
goto out_err;
If a driver is unable or unwilling to deal with a variable number of MSI
interrupts it can request a particular number of interrupts by passing that
number to pci_alloc_irq_vectors() function as both 'min_vecs' and
'max_vecs' parameters:
ret = pci_alloc_irq_vectors(pdev, nvec, nvec, PCI_IRQ_ALL_TYPES);
if (ret < 0)
goto out_err;
The most notorious example of the request type described above is enabling
the single MSI mode for a device. It could be done by passing two 1s as
'min_vecs' and 'max_vecs':
ret = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_ALL_TYPES);
if (ret < 0)
goto out_err;
Some devices might not support using legacy line interrupts, in which case
the driver can specify that only MSI or MSI-X is acceptable:
nvec = pci_alloc_irq_vectors(pdev, 1, nvec, PCI_IRQ_MSI | PCI_IRQ_MSIX);
if (nvec < 0)
goto out_err;
4.3 Legacy APIs
The following old APIs to enable and disable MSI or MSI-X interrupts should
not be used in new code:
pci_enable_msi() /* deprecated */
pci_disable_msi() /* deprecated */
pci_enable_msix_range() /* deprecated */
pci_enable_msix_exact() /* deprecated */
pci_disable_msix() /* deprecated */
Additionally there are APIs to provide the number of supported MSI or MSI-X
vectors: pci_msi_vec_count() and pci_msix_vec_count(). In general these
should be avoided in favor of letting pci_alloc_irq_vectors() cap the
number of vectors. If you have a legitimate special use case for the count
of vectors we might have to revisit that decision and add a
pci_nr_irq_vectors() helper that handles MSI and MSI-X transparently.
4.4 Considerations when using MSIs
4.4.1 Spinlocks
Most device drivers have a per-device spinlock which is taken in the
interrupt handler. With pin-based interrupts or a single MSI, it is not
necessary to disable interrupts (Linux guarantees the same interrupt will
not be re-entered). If a device uses multiple interrupts, the driver
must disable interrupts while the lock is held. If the device sends
a different interrupt, the driver will deadlock trying to recursively
acquire the spinlock. Such deadlocks can be avoided by using
spin_lock_irqsave() or spin_lock_irq() which disable local interrupts
and acquire the lock (see Documentation/kernel-hacking/locking.rst).
4.5 How to tell whether MSI/MSI-X is enabled on a device
Using 'lspci -v' (as root) may show some devices with "MSI", "Message
Signalled Interrupts" or "MSI-X" capabilities. Each of these capabilities
has an 'Enable' flag which is followed with either "+" (enabled)
or "-" (disabled).
5. MSI quirks
Several PCI chipsets or devices are known not to support MSIs.
The PCI stack provides three ways to disable MSIs:
1. globally
2. on all devices behind a specific bridge
3. on a single device
5.1. Disabling MSIs globally
Some host chipsets simply don't support MSIs properly. If we're
lucky, the manufacturer knows this and has indicated it in the ACPI
FADT table. In this case, Linux automatically disables MSIs.
Some boards don't include this information in the table and so we have
to detect them ourselves. The complete list of these is found near the
quirk_disable_all_msi() function in drivers/pci/quirks.c.
If you have a board which has problems with MSIs, you can pass pci=nomsi
on the kernel command line to disable MSIs on all devices. It would be
in your best interests to report the problem to
including a full 'lspci -v' so we can add the quirks to the kernel.
5.2. Disabling MSIs below a bridge
Some PCI bridges are not able to route MSIs between busses properly.
In this case, MSIs must be disabled on all devices behind the bridge.
Some bridges allow you to enable MSIs by changing some bits in their
PCI configuration space (especially the Hypertransport chipsets such
as the nVidia nForce and Serverworks HT2000). As with host chipsets,
Linux mostly knows about them and automatically enables MSIs if it can.
If you have a bridge unknown to Linux, you can enable
MSIs in configuration space using whatever method you know works, then
enable MSIs on that bridge by doing:
echo 1 > /sys/bus/pci/devices/$bridge/msi_bus
where $bridge is the PCI address of the bridge you've enabled (eg
To disable MSIs, echo 0 instead of 1. Changing this value should be
done with caution as it could break interrupt handling for all devices
below this bridge.
Again, please notify of any bridges that need
special handling.
5.3. Disabling MSIs on a single device
Some devices are known to have faulty MSI implementations. Usually this
is handled in the individual device driver, but occasionally it's necessary
to handle this with a quirk. Some drivers have an option to disable use
of MSI. While this is a convenient workaround for the driver author,
it is not good practice, and should not be emulated.
5.4. Finding why MSIs are disabled on a device
From the above three sections, you can see that there are many reasons
why MSIs may not be enabled for a given device. Your first step should
be to examine your dmesg carefully to determine whether MSIs are enabled
for your machine. You should also check your .config to be sure you
have enabled CONFIG_PCI_MSI.
Then, 'lspci -t' gives the list of bridges above a device. Reading
/sys/bus/pci/devices/*/msi_bus will tell you whether MSIs are enabled (1)
or disabled (0). If 0 is found in any of the msi_bus files belonging
to bridges between the PCI root and the device, MSIs are disabled.
It is also worth checking the device driver to see whether it supports MSIs.
For example, it may contain calls to pci_irq_alloc_vectors() with the
The PCI Express Port Bus Driver Guide HOWTO
Tom L Nguyen
1. About this guide
This guide describes the basics of the PCI Express Port Bus driver
and provides information on how to enable the service drivers to
register/unregister with the PCI Express Port Bus Driver.
2. Copyright 2004 Intel Corporation
3. What is the PCI Express Port Bus Driver
A PCI Express Port is a logical PCI-PCI Bridge structure. There
are two types of PCI Express Port: the Root Port and the Switch
Port. The Root Port originates a PCI Express link from a PCI Express
Root Complex and the Switch Port connects PCI Express links to
internal logical PCI buses. The Switch Port, which has its secondary
bus representing the switch's internal routing logic, is called the
switch's Upstream Port. The switch's Downstream Port is bridging from
switch's internal routing bus to a bus representing the downstream
PCI Express link from the PCI Express Switch.
A PCI Express Port can provide up to four distinct functions,
referred to in this document as services, depending on its port type.
PCI Express Port's services include native hotplug support (HP),
power management event support (PME), advanced error reporting
support (AER), and virtual channel support (VC). These services may
be handled by a single complex driver or be individually distributed
and handled by corresponding service drivers.
4. Why use the PCI Express Port Bus Driver?
In existing Linux kernels, the Linux Device Driver Model allows a
physical device to be handled by only a single driver. The PCI
Express Port is a PCI-PCI Bridge device with multiple distinct
services. To maintain a clean and simple solution each service
may have its own software service driver. In this case several
service drivers will compete for a single PCI-PCI Bridge device.
For example, if the PCI Express Root Port native hotplug service
driver is loaded first, it claims a PCI-PCI Bridge Root Port. The
kernel therefore does not load other service drivers for that Root
Port. In other words, it is impossible to have multiple service
drivers load and run on a PCI-PCI Bridge device simultaneously
using the current driver model.
To enable multiple service drivers running simultaneously requires
having a PCI Express Port Bus driver, which manages all populated
PCI Express Ports and distributes all provided service requests
to the corresponding service drivers as required. Some key
advantages of using the PCI Express Port Bus driver are listed below:
- Allow multiple service drivers to run simultaneously on
a PCI-PCI Bridge Port device.
- Allow service drivers implemented in an independent
staged approach.
- Allow one service driver to run on multiple PCI-PCI Bridge
Port devices.
- Manage and distribute resources of a PCI-PCI Bridge Port
device to requested service drivers.
5. Configuring the PCI Express Port Bus Driver vs. Service Drivers
5.1 Including the PCI Express Port Bus Driver Support into the Kernel
Including the PCI Express Port Bus driver depends on whether the PCI
Express support is included in the kernel config. The kernel will
automatically include the PCI Express Port Bus driver as a kernel
driver when the PCI Express support is enabled in the kernel.
5.2 Enabling Service Driver Support
PCI device drivers are implemented based on Linux Device Driver Model.
All service drivers are PCI device drivers. As discussed above, it is
impossible to load any service driver once the kernel has loaded the
PCI Express Port Bus Driver. To meet the PCI Express Port Bus Driver
Model requires some minimal changes on existing service drivers that
imposes no impact on the functionality of existing service drivers.
A service driver is required to use the two APIs shown below to
register its service with the PCI Express Port Bus driver (see
section 5.2.1 & 5.2.2). It is important that a service driver
initializes the pcie_port_service_driver data structure, included in
header file /include/linux/pcieport_if.h, before calling these APIs.
Failure to do so will result an identity mismatch, which prevents
the PCI Express Port Bus driver from loading a service driver.
5.2.1 pcie_port_service_register
int pcie_port_service_register(struct pcie_port_service_driver *new)
This API replaces the Linux Driver Model's pci_register_driver API. A
service driver should always calls pcie_port_service_register at
module init. Note that after service driver being loaded, calls
such as pci_enable_device(dev) and pci_set_master(dev) are no longer
necessary since these calls are executed by the PCI Port Bus driver.
5.2.2 pcie_port_service_unregister
void pcie_port_service_unregister(struct pcie_port_service_driver *new)
pcie_port_service_unregister replaces the Linux Driver Model's
pci_unregister_driver. It's always called by service driver when a
module exits.
5.2.3 Sample Code
Below is sample service driver code to initialize the port service
driver data structure.
static struct pcie_port_service_id service_id[] = { {
.vendor = PCI_ANY_ID,
.device = PCI_ANY_ID,
.port_type = PCIE_RC_PORT,
.service_type = PCIE_PORT_SERVICE_AER,
}, { /* end: all zeroes */ }
static struct pcie_port_service_driver root_aerdrv = {
.name = (char *)device_name,
.id_table = &service_id[0],
.probe = aerdrv_load,
.remove = aerdrv_unload,
.suspend = aerdrv_suspend,
.resume = aerdrv_resume,
Below is a sample code for registering/unregistering a service
static int __init aerdrv_service_init(void)
int retval = 0;
retval = pcie_port_service_register(&root_aerdrv);
if (!retval) {
return retval;
static void __exit aerdrv_service_exit(void)
6. Possible Resource Conflicts
Since all service drivers of a PCI-PCI Bridge Port device are
allowed to run simultaneously, below lists a few of possible resource
conflicts with proposed solutions.
6.1 MSI and MSI-X Vector Resource
Once MSI or MSI-X interrupts are enabled on a device, it stays in this
mode until they are disabled again. Since service drivers of the same
PCI-PCI Bridge port share the same physical device, if an individual
service driver enables or disables MSI/MSI-X mode it may result
unpredictable behavior.
To avoid this situation all service drivers are not permitted to
switch interrupt mode on its device. The PCI Express Port Bus driver
is responsible for determining the interrupt mode and this should be
transparent to service drivers. Service drivers need to know only
the vector IRQ assigned to the field irq of struct pcie_device, which
is passed in when the PCI Express Port Bus driver probes each service
driver. Service drivers should use (struct pcie_device*)dev->irq to
call request_irq/free_irq. In addition, the interrupt mode is stored
in the field interrupt_mode of struct pcie_device.
6.3 PCI Memory/IO Mapped Regions
Service drivers for PCI Express Power Management (PME), Advanced
Error Reporting (AER), Hot-Plug (HP) and Virtual Channel (VC) access
PCI configuration space on the PCI Express port. In all cases the
registers accessed are independent of each other. This patch assumes
that all service drivers will be well behaved and not overwrite
other service driver's configuration settings.
6.4 PCI Config Registers
Each service driver runs its PCI config operations on its own
capability structure except the PCI Express capability structure, in
which Root Control register and Device Control register are shared
between PME and AER. This patch assumes that all service drivers
will be well behaved and not overwrite other service driver's
configuration settings.
.. SPDX-License-Identifier: GPL-2.0
ACPI considerations for PCI host bridges
The general rule is that the ACPI namespace should describe everything the
OS might use unless there's another way for the OS to find it [1, 2].
For example, there's no standard hardware mechanism for enumerating PCI
host bridges, so the ACPI namespace must describe each host bridge, the
method for accessing PCI config space below it, the address space windows
the host bridge forwards to PCI (using _CRS), and the routing of legacy
INTx interrupts (using _PRT).