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Date:   Sun, 31 Mar 2019 23:33:46 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Changbin Du <changbin.du@...il.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/12] pci doc: convert PCI/MSI-HOWTO.txt to rst format

Hi Corbet,
I also plant to convert x86 arch specific docs. And I will merge them into
one big serias for reviewing. Please wait for new revison. Thanks!

On Sat, Mar 30, 2019 at 12:04:06AM +0800, Changbin Du wrote
> 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@...il.com>
> ---
>  .../PCI/{MSI-HOWTO.txt => MSI-HOWTO.rst}      | 56 ++++++++++++-------
>  Documentation/PCI/index.rst                   |  1 +
>  2 files changed, 38 insertions(+), 19 deletions(-)
>  rename Documentation/PCI/{MSI-HOWTO.txt => MSI-HOWTO.rst} (89%)
> 
> diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.rst
> similarity index 89%
> rename from Documentation/PCI/MSI-HOWTO.txt
> rename to Documentation/PCI/MSI-HOWTO.rst
> index 618e13d5e276..33f382632fdd 100644
> --- a/Documentation/PCI/MSI-HOWTO.txt
> +++ b/Documentation/PCI/MSI-HOWTO.rst
> @@ -1,13 +1,18 @@
> -		The MSI Driver Guide HOWTO
> -	Tom L Nguyen tom.l.nguyen@...el.com
> -			10/03/2003
> -	Revised Feb 12, 2004 by Martine Silbermann
> -		email: Martine.Silbermann@...com
> -	Revised Jun 25, 2004 by Tom L Nguyen
> -	Revised Jul  9, 2008 by Matthew Wilcox <willy@...ux.intel.com>
> -		Copyright 2003, 2008 Intel Corporation
> +.. SPDX-License-Identifier: GPL-2.0
> +.. include:: <isonum.txt>
> +
> +==========================
> +The MSI Driver Guide HOWTO
> +==========================
> +
> +:Authors: - Tom L Nguyen <tom.l.nguyen@...el.com> 10/03/2003
> +          - Revised Feb 12, 2004 by Martine Silbermann <Martine.Silbermann@...com>
> +	  - Revised Jun 25, 2004 by Tom L Nguyen
> +	  - Revised Jul  9, 2008 by Matthew Wilcox <willy@...ux.intel.com>
> +	    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
> @@ -16,6 +21,7 @@ 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.
> @@ -30,6 +36,7 @@ a time.
>  
>  
>  3. Why use MSIs?
> +================
>  
>  There are three reasons why using MSIs can give an advantage over
>  traditional pin-based interrupts.
> @@ -62,6 +69,7 @@ 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
> @@ -69,6 +77,7 @@ 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,
> @@ -77,13 +86,14 @@ on x86, you must also enable X86_UP_APIC or SMP in order to see the
>  CONFIG_PCI_MSI option.
>  
>  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
>  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 +111,12 @@ 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 +136,7 @@ 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 +145,7 @@ 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)
> @@ -143,14 +153,14 @@ 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)
> @@ -159,7 +169,7 @@ the driver can specify that only MSI or MSI-X is acceptable:
>  4.3 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 */
> @@ -175,8 +185,10 @@ 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
> @@ -189,6 +201,7 @@ 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
> @@ -197,6 +210,7 @@ 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:
> @@ -206,6 +220,7 @@ The PCI stack provides three ways to disable MSIs:
>  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
> @@ -220,6 +235,7 @@ in your best interests to report the problem to linux-pci@...r.kernel.org
>  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.
> @@ -230,7 +246,7 @@ 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
>  
> @@ -245,6 +261,7 @@ Again, please notify linux-pci@...r.kernel.org 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
> @@ -253,6 +270,7 @@ 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
> @@ -260,8 +278,8 @@ 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 751cd8f23c62..8ed57b9ecfe4 100644
> --- a/Documentation/PCI/index.rst
> +++ b/Documentation/PCI/index.rst
> @@ -10,3 +10,4 @@ Linux PCI Bus Subsystem
>     pci
>     PCIEBUS-HOWTO
>     pci-iov-howto
> +   MSI-HOWTO
> -- 
> 2.20.1
> 

-- 
Cheers,
Changbin Du

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