Re: [Nouveau] [PATCH v2] pci: Handle 5-bit and 8-bit tag field

On Wed, Sep 16, 2015 at 3:52 PM, Pierre Moreau pierre.morrow@free.fr wrote:

If the hardware supports extended tag field (8-bit ones), then enabled it. This is usually done by the VBIOS, but not on some MBPs (see fdo#86537). In case extended tag field is not supported, 5-bit tag field is used which limits the possible values to 32. Apparently bits 7:0 of 0x8841c stores some number of outstanding requests, so cap it to 32 if extended tag is unsupported.

Fixes: fdo#86537

v2: Restrict changes to chipsets >= 0x84

Signed-off-by: Pierre Moreau pierre.morrow@free.fr

drm/nouveau/nvkm/subdev/pci/base.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)

diff --git a/drm/nouveau/nvkm/subdev/pci/base.c b/drm/nouveau/nvkm/subdev/pci/base.c index d1c148e..bbad29d 100644 --- a/drm/nouveau/nvkm/subdev/pci/base.c +++ b/drm/nouveau/nvkm/subdev/pci/base.c @@ -46,6 +46,14 @@ nvkm_pci_wr32(struct nvkm_pci *pci, u16 addr, u32 data) pci->func->wr32(pci, addr, data); }

+u32 +nvkm_pci_mask(struct nvkm_pci *pci, u16 addr, u32 mask, u32 add)

Either add this to the header or make it static. I have a mild preference for the latter.

+{

•   u32 data = pci->func->rd32(pci, addr);
  

•   pci->func->wr32(pci, addr, (data & ~mask) | add);
  

•   return data;
  

+}

void nvkm_pci_rom_shadow(struct nvkm_pci *pci, bool shadow) { @@ -115,6 +123,23 @@ nvkm_pci_init(struct nvkm_subdev *subdev) if (ret) return ret;

•   if (pci_is_pcie(pdev) && subdev->device->chipset >= 0x84) {
  

•           /* Tag field is 8-bit long, regardless of EXT_TAG.
  

•            * However, if EXT_TAG is disabled, only the lower 5 bits of the tag
  

•            * field should be used, limiting the number of request to 32.
  

•            *
  

•            * Apparently, 0x041c stores some limit on the number of requests
  

•            * possible, so if EXT_TAG is disabled, limit that requests number to
  

•            * 32
  

•            *
  

•            * Fixes fdo#86537
  

•            */
  

•           if (nvkm_pci_rd32(pci, 0x007c) & 0x00000020)
  

•                   nvkm_pci_mask(pci, 0x0080, 0x00000000, 0x00000100);
  

Normally this is done as 0x100, 0x100, although your way works. However a future change might mask out any unwanted bits from the value as well...

•           else
  

•                   nvkm_pci_mask(pci, 0x041c, 0x00000060, 0x00000000);
  

•   }
  

•   pci->irq = pdev->irq;
    return ret;
  

}

2.5.2

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