Re: [PATCH v4 29/63] Documentation: PCI: convert MSI-HOWTO.txt to reST

Mauro Carvalho Chehab
2019-04-24T15:30:05Z

Em Wed, 24 Apr 2019 00:28:58 +0800
Changbin Du <changbin.du@gmail.com> escreveu:

> This converts the plain text documentation to reStructuredText format and
> add it to Sphinx TOC tree. No essential content change.
>
> Signed-off-by: Changbin Du <changbin.du@gmail.com>
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
>
> ---
> v2:
> o drop numbering.
> o simplify author list
> ---
> .../PCI/{MSI-HOWTO.txt => MSI-HOWTO.rst} | 83 +++++++++++--------
> Documentation/PCI/index.rst | 1 +
> 2 files changed, 50 insertions(+), 34 deletions(-)
> rename Documentation/PCI/{MSI-HOWTO.txt => MSI-HOWTO.rst} (88%)

Renamed names in lowercase, please.

>
> diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.rst
> similarity index 88%
> rename from Documentation/PCI/MSI-HOWTO.txt
> rename to Documentation/PCI/MSI-HOWTO.rst
> index 618e13d5e276..18cc3700489b 100644
> --- a/Documentation/PCI/MSI-HOWTO.txt
> +++ b/Documentation/PCI/MSI-HOWTO.rst
> @@ -1,13 +1,14 @@
> - The MSI Driver Guide HOWTO
> - Tom L Nguyen tom.l.nguyen@intel.com
> - 10/03/2003
> - Revised Feb 12, 2004 by Martine Silbermann
> - email: Martine.Silbermann@hp.com
> - Revised Jun 25, 2004 by Tom L Nguyen
> - Revised Jul 9, 2008 by Matthew Wilcox <willy@linux.intel.com>
> - Copyright 2003, 2008 Intel Corporation
> +.. SPDX-License-Identifier: GPL-2.0
> +.. include:: <isonum.txt>
>
> -1. About this guide
> +==========================
> +The MSI Driver Guide HOWTO
> +==========================
> +
> +:Authors: Tom L Nguyen; Martine Silbermann; Matthew Wilcox

Not so sure about this, as you removed the author emails.

It seems you missed to keep:

Copyright 2003, 2008 Intel Corporation

After re-adding the missing copyright:

Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

> +
> +About this guide
> +================
>
> This guide describes the basics of Message Signaled Interrupts (MSIs),
> the advantages of using MSI over traditional interrupt mechanisms, how
> @@ -15,7 +16,8 @@ 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?
> +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.
> @@ -29,7 +31,8 @@ Devices may support both MSI and MSI-X, but only one can be enabled at
> a time.
>
>
> -3. Why use MSIs?
> +Why use MSIs?
> +=============
>
> There are three reasons why using MSIs can give an advantage over
> traditional pin-based interrupts.
> @@ -61,14 +64,16 @@ 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
> +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
> +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,
> @@ -76,14 +81,15 @@ 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
> CONFIG_PCI_MSI option.
>
> -4.2 Using MSI
> +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
> device.
>
> To automatically use MSI or MSI-X interrupt vectors, use the following
> -function:
> +function::
>
> int pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
> unsigned int max_vecs, unsigned int flags);
> @@ -101,12 +107,12 @@ 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:
> +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:
> +the following function::
>
> void pci_free_irq_vectors(struct pci_dev *dev);
>
> @@ -126,7 +132,7 @@ 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:
> +vectors supported beforehand::
>
> nvec = pci_alloc_irq_vectors(pdev, 1, nvec, PCI_IRQ_ALL_TYPES)
> if (nvec < 0)
> @@ -135,7 +141,7 @@ vectors supported beforehand:
> 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:
> +'max_vecs' parameters::
>
> ret = pci_alloc_irq_vectors(pdev, nvec, nvec, PCI_IRQ_ALL_TYPES);
> if (ret < 0)
> @@ -143,23 +149,24 @@ number to pci_alloc_irq_vectors() function as both 'min_vecs' and
>
> 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':
> +'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:
> +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
> +Legacy APIs
> +-----------
>
> The following old APIs to enable and disable MSI or MSI-X interrupts should
> -not be used in new code:
> +not be used in new code::
>
> pci_enable_msi() /* deprecated */
> pci_disable_msi() /* deprecated */
> @@ -174,9 +181,11 @@ 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
> +Considerations when using MSIs
> +------------------------------
>
> -4.4.1 Spinlocks
> +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
> @@ -188,7 +197,8 @@ 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
> +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
> @@ -196,7 +206,8 @@ has an 'Enable' flag which is followed with either "+" (enabled)
> or "-" (disabled).
>
>
> -5. MSI quirks
> +MSI quirks
> +==========
>
> Several PCI chipsets or devices are known not to support MSIs.
> The PCI stack provides three ways to disable MSIs:
> @@ -205,7 +216,8 @@ The PCI stack provides three ways to disable MSIs:
> 2. on all devices behind a specific bridge
> 3. on a single device
>
> -5.1. Disabling MSIs globally
> +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
> @@ -219,7 +231,8 @@ on the kernel command line to disable MSIs on all devices. It would be
> in your best interests to report the problem to linux-pci@vger.kernel.org
> including a full 'lspci -v' so we can add the quirks to the kernel.
>
> -5.2. Disabling MSIs below a bridge
> +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.
> @@ -230,7 +243,7 @@ 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:
> +enable MSIs on that bridge by doing::
>
> echo 1 > /sys/bus/pci/devices/$bridge/msi_bus
>
> @@ -244,7 +257,8 @@ below this bridge.
> Again, please notify linux-pci@vger.kernel.org of any bridges that need
> special handling.
>
> -5.3. Disabling MSIs on a single device
> +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
> @@ -252,7 +266,8 @@ 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
> +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
> @@ -260,8 +275,8 @@ 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)
> +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.
>
> diff --git a/Documentation/PCI/index.rst b/Documentation/PCI/index.rst
> index e1c19962a7f8..1b25bcc1edca 100644
> --- a/Documentation/PCI/index.rst
> +++ b/Documentation/PCI/index.rst
> @@ -11,3 +11,4 @@ Linux PCI Bus Subsystem
> pci
> PCIEBUS-HOWTO
> pci-iov-howto
> + MSI-HOWTO

Thanks,
Mauro