drm/nouveau/pci: Handle 5-bit and 8-bit tag field

If the hardware supports extended tag field (8-bit ones), then enable 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 number of requests to 32. Apparently bits 7:0 of
0x08841c 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
v3:
  * Add nvkm_pci_mask to pci.h
  * Mask bit 8 before setting it
v4:
  * Rename `add` argument of nvkm_pci_mask to `value`
  * Move code from nvkm_pci_init to g84_pci_init and remove PCIe and chipset
    checks
v5:
  * Rebase code on latest PCI structure
  * Restore PCIe check
  * Fix namings in nvkm_pci_mask
  * Rephrase part of the commit message

Signed-off-by: Pierre Moreau <pierre.morrow@free.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/base.c
index 21106223c2c3..d671dcfaff3c 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/base.c
+++ b/drivers/gpu/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 value)
+{
+	u32 data = pci->func->rd32(pci, addr);
+	pci->func->wr32(pci, addr, (data & ~mask) | value);
+	return data;
+}
+
 void
 nvkm_pci_rom_shadow(struct nvkm_pci *pci, bool shadow)
 {