3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx> [ Upstream commit 88b333b0ed790f9433ff542b163bf972953b74d3 ] Currently the value written to CP_RB_WPTR is calculated on the fly as (rb->next - rb->start). But as the code is designed rb->next is wrapped before writing the commands so if a series of commands happened to fit perfectly in the ringbuffer, rb->next would end up being equal to rb->size / 4 and thus result in an out of bounds address to CP_RB_WPTR. The easiest way to fix this is to mask WPTR when writing it to the hardware; it makes the hardware happy and the rest of the ringbuffer math appears to work and there isn't any point in upsetting anything. Signed-off-by: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx> [squash in is_power_of_2() check] Signed-off-by: Rob Clark <robdclark@xxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/msm/adreno/adreno_gpu.c | 9 ++++++++- drivers/gpu/drm/msm/msm_ringbuffer.c | 3 ++- 2 files changed, 10 insertions(+), 2 deletions(-) --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c @@ -199,7 +199,14 @@ void adreno_flush(struct msm_gpu *gpu) void adreno_idle(struct msm_gpu *gpu) { struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu); - uint32_t wptr = get_wptr(gpu->rb); + uint32_t wptr; + + /* + * Mask wptr value that we calculate to fit in the HW range. This is + * to account for the possibility that the last command fit exactly into + * the ringbuffer and rb->next hasn't wrapped to zero yet + */ + wptr = get_wptr(gpu->rb) & ((gpu->rb->size / 4) - 1); /* wait for CP to drain ringbuffer: */ if (spin_until(adreno_gpu->memptrs->rptr == wptr)) --- a/drivers/gpu/drm/msm/msm_ringbuffer.c +++ b/drivers/gpu/drm/msm/msm_ringbuffer.c @@ -23,7 +23,8 @@ struct msm_ringbuffer *msm_ringbuffer_ne struct msm_ringbuffer *ring; int ret; - size = ALIGN(size, 4); /* size should be dword aligned */ + if (WARN_ON(!is_power_of_2(size))) + return ERR_PTR(-EINVAL); ring = kzalloc(sizeof(*ring), GFP_KERNEL); if (!ring) {