To avoid harmful compiler optimizations and IO reordering in the HW, use barriers and READ/WRITE_ONCE helpers as necessary while accessing the HFI queue index variables.
Signed-off-by: Akhil P Oommen <[email protected]> --- drivers/gpu/drm/msm/adreno/a6xx_hfi.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c index 2daaa340366d..aef00c2dd137 100644 --- a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c +++ b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c @@ -34,7 +34,7 @@ static int a6xx_hfi_queue_read(struct a6xx_gmu *gmu, struct a6xx_hfi_queue_header *header = queue->header; u32 i, hdr, index = header->read_index; - if (header->read_index == header->write_index) { + if (header->read_index == READ_ONCE(header->write_index)) { header->rx_request = 1; return 0; } @@ -62,7 +62,10 @@ static int a6xx_hfi_queue_read(struct a6xx_gmu *gmu, if (!gmu->legacy) index = ALIGN(index, 4) % header->size; - header->read_index = index; + /* Ensure all memory operations are complete before updating the read index */ + dma_mb(); + + WRITE_ONCE(header->read_index, index); return HFI_HEADER_SIZE(hdr); } @@ -74,7 +77,7 @@ static int a6xx_hfi_queue_write(struct a6xx_gmu *gmu, spin_lock(&queue->lock); - space = CIRC_SPACE(header->write_index, header->read_index, + space = CIRC_SPACE(header->write_index, READ_ONCE(header->read_index), header->size); if (space < dwords) { header->dropped++; @@ -95,7 +98,10 @@ static int a6xx_hfi_queue_write(struct a6xx_gmu *gmu, queue->data[index] = 0xfafafafa; } - header->write_index = index; + /* Ensure all memory operations are complete before updating the write index */ + dma_mb(); + + WRITE_ONCE(header->write_index, index); spin_unlock(&queue->lock); gmu_write(gmu, REG_A6XX_GMU_HOST2GMU_INTR_SET, 0x01); -- 2.51.0
