From 656ebbda99312d2cc558deb928caec657286fa0c Mon Sep 17 00:00:00 2001 From: Karol Herbst Date: Tue, 13 Oct 2020 14:01:26 +0200 Subject: [PATCH] drm/nouveau/device: fix changing endianess code to work on older GPUs commit dcd292c172493067a72672b245a3dd1bcf7268dd upstream. With this we try to detect if the endianess switch works and assume LE if not. Suggested by Ben. Fixes: 51c05340e407 ("drm/nouveau/device: detect if changing endianness failed") Signed-off-by: Karol Herbst Cc: # v5.8+ Signed-off-by: Ben Skeggs Signed-off-by: Greg Kroah-Hartman --- .../gpu/drm/nouveau/nvkm/engine/device/base.c | 39 ++++++++++++------- 1 file changed, 26 insertions(+), 13 deletions(-) diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/device/base.c b/drivers/gpu/drm/nouveau/nvkm/engine/device/base.c index dcb70677d0acc..7851bec5f0e5f 100644 --- a/drivers/gpu/drm/nouveau/nvkm/engine/device/base.c +++ b/drivers/gpu/drm/nouveau/nvkm/engine/device/base.c @@ -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);