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    Subject[PATCH 5.10 319/717] drm/msm: a5xx: Make preemption reset case reentrant
    Date
    From: Marijn Suijten <marijn.suijten@somainline.org>

    [ Upstream commit 7cc29fcdfcc8784e97c5151c848e193800ec79ac ]

    nr_rings is reset to 1, but when this function is called for a second
    (and third!) time nr_rings > 1 is false, thus the else case is entered
    to set up a buffer for the RPTR shadow and consequently written to
    RB_RPTR_ADDR, hanging platforms without WHERE_AM_I firmware support.

    Restructure the condition in such a way that shadow buffer setup only
    ever happens when has_whereami is true; otherwise preemption is only
    finalized when the number of ring buffers has not been reset to 1 yet.

    Fixes: 8907afb476ac ("drm/msm: Allow a5xx to mark the RPTR shadow as privileged")
    Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
    Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
    Reviewed-by: Jordan Crouse <jcrouse@codeaurora.org>
    Signed-off-by: Rob Clark <robdclark@chromium.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/gpu/drm/msm/adreno/a5xx_gpu.c | 12 ++++++------
    1 file changed, 6 insertions(+), 6 deletions(-)

    diff --git a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
    index 8aa08976aad17..69ed2c6094665 100644
    --- a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
    +++ b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
    @@ -755,12 +755,8 @@ static int a5xx_hw_init(struct msm_gpu *gpu)
    gpu_write(gpu, REG_A5XX_CP_RB_CNTL,
    MSM_GPU_RB_CNTL_DEFAULT | AXXX_CP_RB_CNTL_NO_UPDATE);

    - /* Disable preemption if WHERE_AM_I isn't available */
    - if (!a5xx_gpu->has_whereami && gpu->nr_rings > 1) {
    - a5xx_preempt_fini(gpu);
    - gpu->nr_rings = 1;
    - } else {
    - /* Create a privileged buffer for the RPTR shadow */
    + /* Create a privileged buffer for the RPTR shadow */
    + if (a5xx_gpu->has_whereami) {
    if (!a5xx_gpu->shadow_bo) {
    a5xx_gpu->shadow = msm_gem_kernel_new(gpu->dev,
    sizeof(u32) * gpu->nr_rings,
    @@ -774,6 +770,10 @@ static int a5xx_hw_init(struct msm_gpu *gpu)

    gpu_write64(gpu, REG_A5XX_CP_RB_RPTR_ADDR,
    REG_A5XX_CP_RB_RPTR_ADDR_HI, shadowptr(a5xx_gpu, gpu->rb[0]));
    + } else if (gpu->nr_rings > 1) {
    + /* Disable preemption if WHERE_AM_I isn't available */
    + a5xx_preempt_fini(gpu);
    + gpu->nr_rings = 1;
    }

    a5xx_preempt_hw_init(gpu);
    --
    2.27.0


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