linux-kernel - Re: [PATCH v4 4/5] PCI: iproc: Add iProc PCIe MSI support

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Date:	Wed, 2 Dec 2015 15:30:03 +0100
From:	Hauke Mehrtens <hauke@...ke-m.de>
To:	Ray Jui <rjui@...adcom.com>, Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Marc Zyngier <marc.zyngier@....com>, Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org,
	bcm-kernel-feedback-list@...adcom.com, linux-pci@...r.kernel.org
Subject: Re: [PATCH v4 4/5] PCI: iproc: Add iProc PCIe MSI support

On 11/27/2015 06:37 PM, Ray Jui wrote:
> This patch adds PCIe MSI support for both PAXB and PAXC interfaces on
> all iProc based platforms
> 
> The iProc PCIe MSI support deploys an event queue based implementation.
> Each event queue is serviced by a GIC interrupt and can support up to 64
> MSI vectors. Host memory is allocated for the event queues, and each event
> queue consists of 64 word-sized entries. MSI data is written to the
> lower 16-bit of each entry, whereas the upper 16-bit of the entry is
> reserved for the controller for internal processing
> 
> Each event queue is tracked by a head pointer and tail pointer. Head
> pointer indicates the next entry in the event queue to be processed by
> the driver and is updated by the driver after processing is done.
> The controller uses the tail pointer as the next MSI data insertion
> point. The controller ensures MSI data is flushed to host memory before
> updating the tail pointer and then triggering the interrupt
> 
> MSI IRQ affinity is supported by evenly distributing the interrupts to
> each CPU core. MSI vector is moved from one GIC interrupt to another in
> order to steer to the target CPU
> 
> Therefore, the actual number of supported MSI vectors is:
> 
> M * 64 / N
> 
> where M denotes the number of GIC interrupts (event queues), and N
> denotes the number of CPU cores
> 
> This iProc event queue based MSI support should not be used with newer
> platforms with integrated MSI support in the GIC (e.g., giv2m or
> gicv3-its)
> 
> Signed-off-by: Ray Jui <rjui@...adcom.com>
> Reviewed-by: Anup Patel <anup.patel@...adcom.com>
> Reviewed-by: Vikram Prakash <vikramp@...adcom.com>
> Reviewed-by: Scott Branden <sbranden@...adcom.com>
> ---
>  drivers/pci/host/Kconfig               |   9 +
>  drivers/pci/host/Makefile              |   1 +
>  drivers/pci/host/pcie-iproc-bcma.c     |   1 +
>  drivers/pci/host/pcie-iproc-msi.c      | 675 +++++++++++++++++++++++++++++++++
>  drivers/pci/host/pcie-iproc-platform.c |   1 +
>  drivers/pci/host/pcie-iproc.c          |  26 ++
>  drivers/pci/host/pcie-iproc.h          |  23 +-
>  7 files changed, 734 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/pci/host/pcie-iproc-msi.c
> 

.....
>  
>  int iproc_pcie_setup(struct iproc_pcie *pcie, struct list_head *res);
>  int iproc_pcie_remove(struct iproc_pcie *pcie);
>  
> +#ifdef CONFIG_PCI_MSI
> +int iproc_msi_init(struct iproc_pcie *pcie, struct device_node *node);
> +void iproc_msi_exit(struct iproc_pcie *pcie);
> +#else
> +static inline int iproc_msi_init(struct iproc_pcie *pcie,
> +				 struct device_node *node)
> +{
> +	return -ENODEV;
> +}
> +static void iproc_msi_exit(struct iproc_pcie *pcie)

Please use static inline here.

> +{
> +}
> +#endif
> +
>  #endif /* _PCIE_IPROC_H */
> 

Hauke
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