linux-kernel - Re: [PATCH - v4] PCI: keystone: add a pci quirk to limit mrrs

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Date:	Tue, 16 Sep 2014 15:54:48 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Murali Karicheri <m-karicheri2@...com>
Cc:	linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, jgunthorpe@...idianresearch.com
Subject: Re: [PATCH - v4] PCI: keystone: add a pci quirk to limit mrrs

On Mon, Sep 08, 2014 at 01:03:34PM -0400, Murali Karicheri wrote:
> Keystone PCI controller has a limitation that memory read request
> size must not exceed 256 bytes. This is a hardware limitation and
> add a quirk to force this limit on all downstream devices by
> updating mrrs.
> 
> Signed-off-by: Murali Karicheri <m-karicheri2@...com>

Applied to pci/host-keystone for v3.18, thanks.

I moved the pci-keystone.txt update regarding pci=pcie_bus_perf into this
patch.  This is where it belongs, isn't it?  I'm pretty sure it wasn't
related to setting the PCI device ID dynamically.

> ---
>   -v4: re-send removing extra lines
>   -v3: added check for vendor id and use pci_matc_id() to do matching
>   -v2: made the quirk happens after tuning
>   -v1: changed printk to indicate PCI bdf
> 
>  drivers/pci/host/pci-keystone.c |   45 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/drivers/pci/host/pci-keystone.c b/drivers/pci/host/pci-keystone.c
> index c1cfaef..ff8ed25 100644
> --- a/drivers/pci/host/pci-keystone.c
> +++ b/drivers/pci/host/pci-keystone.c
> @@ -42,8 +42,53 @@
>  /* DEV_STAT_CTRL */
>  #define PCIE_CAP_BASE		0x70
>  
> +/* PCIE controller device IDs */
> +#define PCIE_RC_K2HK		0xb008
> +#define PCIE_RC_K2E		0xb009
> +#define PCIE_RC_K2L		0xb00a
> +
>  #define to_keystone_pcie(x)	container_of(x, struct keystone_pcie, pp)
>  
> +static void quirk_limit_mrrs(struct pci_dev *dev)
> +{
> +	struct pci_bus *bus = dev->bus;
> +	struct pci_dev *bridge = bus->self;
> +	static const struct pci_device_id rc_pci_devids[] = {
> +		{ PCI_DEVICE(PCI_VENDOR_ID_TI, PCIE_RC_K2HK),
> +		 .class = PCI_CLASS_BRIDGE_PCI << 8, .class_mask = ~0, },
> +		{ PCI_DEVICE(PCI_VENDOR_ID_TI, PCIE_RC_K2E),
> +		 .class = PCI_CLASS_BRIDGE_PCI << 8, .class_mask = ~0, },
> +		{ PCI_DEVICE(PCI_VENDOR_ID_TI, PCIE_RC_K2L),
> +		 .class = PCI_CLASS_BRIDGE_PCI << 8, .class_mask = ~0, },
> +		{ 0, },
> +	};
> +
> +	if (pci_is_root_bus(bus))
> +		return;
> +
> +	/* look for the host bridge */
> +	while (!pci_is_root_bus(bus)) {
> +		bridge = bus->self;
> +		bus = bus->parent;
> +	}
> +
> +	if (bridge) {
> +		/*
> +		 * Keystone PCI controller has a h/w limitation of
> +		 * 256 bytes maximum read request size. It can't handle
> +		 * anything higher than this. So force this limit on
> +		 * all downstream devices
> +		 */
> +		if (pci_match_id(rc_pci_devids, bridge)) {
> +			if (pcie_get_readrq(dev) > 256) {
> +				dev_info(&dev->dev, "limiting mrrs to 256\n");
> +				pcie_set_readrq(dev, 256);
> +			}
> +		}
> +	}
> +}
> +DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID, quirk_limit_mrrs);
> +
>  static int ks_pcie_establish_link(struct keystone_pcie *ks_pcie)
>  {
>  	struct pcie_port *pp = &ks_pcie->pp;
> -- 
> 1.7.9.5
> 
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