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Message-ID: <CAErSpo6Pd1O_vzhiwrRX_fjjoDs789orX_t+uJoZKbk5XWZa6w@mail.gmail.com>
Date: Fri, 7 Sep 2012 13:53:03 -0700
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: Alexander Gordeev <agordeev@...hat.com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Suresh Siddha <suresh.b.siddha@...el.com>,
Yinghai Lu <yinghai@...nel.org>,
Jeff Garzik <jgarzik@...ox.com>,
Matthew Wilcox <willy@...ux.intel.com>, x86@...nel.org,
linux-pci@...r.kernel.org, linux-ide@...r.kernel.org
Subject: Re: [PATCH v2 -tip 4/5] PCI, MSI: Enable multiple MSIs with pci_enable_msi_block_auto()
On Mon, Sep 3, 2012 at 2:19 AM, Alexander Gordeev <agordeev@...hat.com> wrote:
> The new function pci_enable_msi_block_auto() tries to allocate maximum
> possible number of MSIs up to the number the device supports. It
> generalizes a pattern when pci_enable_msi_block() is contiguously called
> until it succeeds or fails.
>
> Opposite to pci_enable_msi_block() which takes the number of MSIs to
> allocate as a input parameter, pci_enable_msi_block_auto() could be used
> by device drivers to obtain the number of assigned MSIs and the number
> of MSIs the device supports.
>
> Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
I haven't looked at the other patches in this series, but if the
x86/IRQ folks like them, I'm OK with this part.
Since the series is mostly non-PCI, I think it makes the most sense to
keep it all together and merge it through some x86 or IRQ tree,
including this PCI bit.
> ---
> Documentation/PCI/MSI-HOWTO.txt | 37 ++++++++++++++++++++++++++++++++-----
> drivers/pci/msi.c | 26 ++++++++++++++++++++++++++
> include/linux/pci.h | 7 +++++++
> 3 files changed, 65 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
> index 53e6fca..a091780 100644
> --- a/Documentation/PCI/MSI-HOWTO.txt
> +++ b/Documentation/PCI/MSI-HOWTO.txt
> @@ -127,15 +127,42 @@ on the number of vectors that can be allocated; pci_enable_msi_block()
> returns as soon as it finds any constraint that doesn't allow the
> call to succeed.
>
> -4.2.3 pci_disable_msi
> +4.2.3 pci_enable_msi_block_auto
> +
> +int pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *count)
> +
> +This variation on pci_enable_msi() call allows a device driver to request
> +the maximum possible number of MSIs. The MSI specification only allows
> +interrupts to be allocated in powers of two, up to a maximum of 2^5 (32).
> +
> +If this function returns a positive number, it indicates that it has
> +succeeded and the returned value is the number of allocated interrupts. In
> +this case, the function enables MSI on this device and updates dev->irq to
> +be the lowest of the new interrupts assigned to it. The other interrupts
> +assigned to the device are in the range dev->irq to dev->irq + returned
> +value - 1.
> +
> +If this function returns a negative number, it indicates an error and
> +the driver should not attempt to request any more MSI interrupts for
> +this device.
> +
> +If the device driver needs to know the number of interrupts the device
> +supports it can pass the pointer count where that number is stored. The
> +device driver must decide what action to take if pci_enable_msi_block_auto()
> +succeeds, but returns a value less than the number of interrupts supported.
> +If the device driver does not need to know the number of interrupts
> +supported, it can set the pointer count to NULL.
> +
> +4.2.4 pci_disable_msi
>
> void pci_disable_msi(struct pci_dev *dev)
>
> This function should be used to undo the effect of pci_enable_msi() or
> -pci_enable_msi_block(). Calling it restores dev->irq to the pin-based
> -interrupt number and frees the previously allocated message signaled
> -interrupt(s). The interrupt may subsequently be assigned to another
> -device, so drivers should not cache the value of dev->irq.
> +pci_enable_msi_block() or pci_enable_msi_block_auto(). Calling it restores
> +dev->irq to the pin-based interrupt number and frees the previously
> +allocated message signaled interrupt(s). The interrupt may subsequently be
> +assigned to another device, so drivers should not cache the value of
> +dev->irq.
>
> Before calling this function, a device driver must always call free_irq()
> on any interrupt for which it previously called request_irq().
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index f0752d1..690b268 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -845,6 +845,32 @@ int pci_enable_msi_block(struct pci_dev *dev, unsigned int nvec)
> }
> EXPORT_SYMBOL(pci_enable_msi_block);
>
> +int pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *maxvec)
> +{
> + int ret, pos, nvec;
> + u16 msgctl;
> +
> + pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
> + if (!pos)
> + return -EINVAL;
> +
> + pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &msgctl);
> + ret = 1 << ((msgctl & PCI_MSI_FLAGS_QMASK) >> 1);
> +
> + if (maxvec)
> + *maxvec = ret;
> +
> + do {
> + nvec = ret;
> + ret = pci_enable_msi_block(dev, nvec);
> + } while (ret > 0);
> +
> + if (ret < 0)
> + return ret;
> + return nvec;
> +}
> +EXPORT_SYMBOL(pci_enable_msi_block_auto);
> +
> void pci_msi_shutdown(struct pci_dev *dev)
> {
> struct msi_desc *desc;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 5faa831..b8a9454 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1070,6 +1070,12 @@ static inline int pci_enable_msi_block(struct pci_dev *dev, unsigned int nvec)
> return -1;
> }
>
> +static inline int
> +pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *maxvec)
> +{
> + return -1;
> +}
> +
> static inline void pci_msi_shutdown(struct pci_dev *dev)
> { }
> static inline void pci_disable_msi(struct pci_dev *dev)
> @@ -1101,6 +1107,7 @@ static inline int pci_msi_enabled(void)
> }
> #else
> extern int pci_enable_msi_block(struct pci_dev *dev, unsigned int nvec);
> +extern int pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *maxvec);
> extern void pci_msi_shutdown(struct pci_dev *dev);
> extern void pci_disable_msi(struct pci_dev *dev);
> extern int pci_msix_table_size(struct pci_dev *dev);
> --
> 1.7.7.6
>
>
> --
> Regards,
> Alexander Gordeev
> agordeev@...hat.com
--
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