linux-kernel - Re: [PATCH v2 10/10] intel-gtt: Read 64bit for gmar_bus

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Date:	Fri, 20 Dec 2013 17:27:23 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Gu Zheng <guz.fnst@...fujitsu.com>,
	Guo Chao <yan@...ux.vnet.ibm.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH v2 10/10] intel-gtt: Read 64bit for gmar_bus_addr

On Mon, Nov 25, 2013 at 6:28 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> That bar could be 64bit pref mem and above 4G.
>
> -v2: refresh to 3.13-rc1
>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> Cc: David Airlie <airlied@...ux.ie>
> Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
> ---
>  drivers/char/agp/intel-gtt.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
> index b8e2014..b929e9d 100644
> --- a/drivers/char/agp/intel-gtt.c
> +++ b/drivers/char/agp/intel-gtt.c
> @@ -609,8 +609,10 @@ static bool intel_gtt_can_wc(void)
>  static int intel_gtt_init(void)
>  {
>         u32 gma_addr;
> +       u32 addr_hi = 0;
>         u32 gtt_map_size;
>         int ret;
> +       int pos;
>
>         ret = intel_private.driver->setup();
>         if (ret != 0)
> @@ -660,13 +662,17 @@ static int intel_gtt_init(void)
>         }
>
>         if (INTEL_GTT_GEN <= 2)
> -               pci_read_config_dword(intel_private.pcidev, I810_GMADDR,
> -                                     &gma_addr);
> +               pos = I810_GMADDR;
>         else
> -               pci_read_config_dword(intel_private.pcidev, I915_GMADDR,
> -                                     &gma_addr);
> +               pos = I915_GMADDR;
> +
> +       pci_read_config_dword(intel_private.pcidev, pos, &gma_addr);
> +
> +       if (gma_addr & PCI_BASE_ADDRESS_MEM_TYPE_64)
> +               pci_read_config_dword(intel_private.pcidev, pos + 4, &addr_hi);

Why are we reading these BARs directly anyway?  These look like
standard PCI BARs (I810_GMADDR == 0x10 and I915_GMADDR == 0x18), so
the PCI core should already be reading them correctly, shouldn't it?
Can't we just use pcibios_resource_to_bus(pci_resource_start())?

It looks like i810_setup(), i830_setup(), and i9xx_setup() have the
same problem and should also be using pci_resource_start() or
something similar.

And I'm confused because the i915_gmch_probe() path fills in
gtt->mappable_base with the bus address, but the gen6_gmch_probe()
path uses the resource, i.e., the CPU, address.  That looks broken to
me.

agp_serverworks_probe() looks like another place that should not be
reading the BARs directly.

>
>         intel_private.gma_bus_addr = (gma_addr & PCI_BASE_ADDRESS_MEM_MASK);
> +       intel_private.gma_bus_addr |= (u64)addr_hi << 32;
>
>         return 0;
>  }
> --
> 1.8.1.4
>
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