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drm/nouveau/device: fix changing endianess code to work on older GPUs

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With this we try to detect if the endianess switch works and assume LE if
not. Suggested by Ben.

Fixes: 51c05340e4 ("drm/nouveau/device: detect if changing endianness failed")
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Cc: <stable@vger.kernel.org> # v5.8+
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
This commit is contained in:
Karol Herbst 2020-10-13 14:01:26 +02:00 committed by Ben Skeggs
parent 925681454d
commit dcd292c172
1 changed files with 26 additions and 13 deletions
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39
drivers/gpu/drm/nouveau/nvkm/engine/device/base.c
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@ -2924,17 +2924,34 @@ nvkm_device_del(struct nvkm_device **pdevice)
}
}
/* returns true if the GPU is in the CPU native byte order */
static inline bool
nvkm_device_endianness(struct nvkm_device *device)
{
u32 boot1 = nvkm_rd32(device, 0x000004) & 0x01000001;
#ifdef __BIG_ENDIAN
if (!boot1)
return false;
const bool big_endian = true;
#else
if (boot1)
return false;
const bool big_endian = false;
#endif
/* Read NV_PMC_BOOT_1, and assume non-functional endian switch if it
* doesn't contain the expected values.
*/
u32 pmc_boot_1 = nvkm_rd32(device, 0x000004);
if (pmc_boot_1 && pmc_boot_1 != 0x01000001)
return !big_endian; /* Assume GPU is LE in this case. */
/* 0 means LE and 0x01000001 means BE GPU. Condition is true when
* GPU/CPU endianness don't match.
*/
if (big_endian == !pmc_boot_1) {
nvkm_wr32(device, 0x000004, 0x01000001);
nvkm_rd32(device, 0x000000);
if (nvkm_rd32(device, 0x000004) != (big_endian ? 0x01000001 : 0x00000000))
return !big_endian; /* Assume GPU is LE on any unexpected read-back. */
}
/* CPU/GPU endianness should (hopefully) match. */
return true;
}
@ -2987,14 +3004,10 @@ nvkm_device_ctor(const struct nvkm_device_func *func,
if (detect) {
/* switch mmio to cpu's native endianness */
if (!nvkm_device_endianness(device)) {
nvkm_wr32(device, 0x000004, 0x01000001);
nvkm_rd32(device, 0x000000);
if (!nvkm_device_endianness(device)) {
nvdev_error(device,
"GPU not supported on big-endian\n");
ret = -ENOSYS;
goto done;
}
nvdev_error(device,
"Couldn't switch GPU to CPUs endianess\n");
ret = -ENOSYS;
goto done;
}
boot0 = nvkm_rd32(device, 0x000000);