6.6-stable review patch. If anyone has any objections, please let me know.
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From: Konrad Dybcio konrad.dybcio@linaro.org
[ Upstream commit 43ec1a202cfa9f765412d325b93873284e7c3d82 ]
Memory barriers help ensure instruction ordering, NOT time and order of actual write arrival at other observers (e.g. memory-mapped IP). On architectures employing weak memory ordering, the latter can be a giant pain point, and it has been as part of this driver.
Moreover, the gpu_/gmu_ accessors already use non-relaxed versions of readl/writel, which include r/w (respectively) barriers.
Replace the barriers with a readback (or drop altogether where possible) that ensures the previous writes have exited the write buffer (as the CPU must flush the write to the register it's trying to read back).
Signed-off-by: Konrad Dybcio konrad.dybcio@linaro.org Patchwork: https://patchwork.freedesktop.org/patch/600869/ Reviewed-by: Akhil P Oommen quic_akhilpo@quicinc.com Signed-off-by: Rob Clark robdclark@chromium.org Stable-dep-of: f248d5d5159a ("drm/msm/a6xx: Fix PDC sleep sequence") Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 4 +--- drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 10 ++++++---- 2 files changed, 7 insertions(+), 7 deletions(-)
--- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c @@ -460,9 +460,7 @@ static int a6xx_rpmh_start(struct a6xx_g int ret; u32 val;
- gmu_write(gmu, REG_A6XX_GMU_RSCC_CONTROL_REQ, 1 << 1); - /* Wait for the register to finish posting */ - wmb(); + gmu_write(gmu, REG_A6XX_GMU_RSCC_CONTROL_REQ, BIT(1));
ret = gmu_poll_timeout(gmu, REG_A6XX_GMU_RSCC_CONTROL_ACK, val, val & (1 << 1), 100, 10000); --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c @@ -1209,14 +1209,16 @@ static int hw_init(struct msm_gpu *gpu) /* Clear GBIF halt in case GX domain was not collapsed */ if (adreno_is_a619_holi(adreno_gpu)) { gpu_write(gpu, REG_A6XX_GBIF_HALT, 0); + gpu_read(gpu, REG_A6XX_GBIF_HALT); + gpu_write(gpu, REG_A6XX_RBBM_GPR0_CNTL, 0); - /* Let's make extra sure that the GPU can access the memory.. */ - mb(); + gpu_read(gpu, REG_A6XX_RBBM_GPR0_CNTL); } else if (a6xx_has_gbif(adreno_gpu)) { gpu_write(gpu, REG_A6XX_GBIF_HALT, 0); + gpu_read(gpu, REG_A6XX_GBIF_HALT); + gpu_write(gpu, REG_A6XX_RBBM_GBIF_HALT, 0); - /* Let's make extra sure that the GPU can access the memory.. */ - mb(); + gpu_read(gpu, REG_A6XX_RBBM_GBIF_HALT); }
gpu_write(gpu, REG_A6XX_RBBM_SECVID_TSB_CNTL, 0);