diff options
Diffstat (limited to 'drivers/dma/altera-msgdma.c')
| -rw-r--r-- | drivers/dma/altera-msgdma.c | 24 |
1 files changed, 15 insertions, 9 deletions
diff --git a/drivers/dma/altera-msgdma.c b/drivers/dma/altera-msgdma.c index b46999c81df0..e23e5b441a24 100644 --- a/drivers/dma/altera-msgdma.c +++ b/drivers/dma/altera-msgdma.c @@ -496,6 +496,11 @@ static void msgdma_copy_one(struct msgdma_device *mdev, { void __iomem *hw_desc = mdev->desc; + /* Ensure control is the last field — required for correct FIFO flush ordering */ + static_assert(offsetof(struct msgdma_extended_desc, control) == + sizeof(struct msgdma_extended_desc) - sizeof(u32), + "control must be the last field in msgdma_extended_desc"); + /* * Check if the DESC FIFO it not full. If its full, we need to wait * for at least one entry to become free again @@ -504,17 +509,18 @@ static void msgdma_copy_one(struct msgdma_device *mdev, MSGDMA_CSR_STAT_DESC_BUF_FULL) mdelay(1); + /* Ensure control is the last field — required for correct FIFO flush ordering */ + static_assert(offsetof(struct msgdma_extended_desc, control) == + sizeof(struct msgdma_extended_desc) - sizeof(u32), + "control must be the last field in msgdma_extended_desc"); + /* - * The descriptor needs to get copied into the descriptor FIFO - * of the DMA controller. The descriptor will get flushed to the - * FIFO, once the last word (control word) is written. Since we - * are not 100% sure that memcpy() writes all word in the "correct" - * order (address from low to high) on all architectures, we make - * sure this control word is written last by single coding it and - * adding some write-barriers here. + * Copy the descriptor into the descriptor FIFO of the DMA controller, + * excluding the control word. The FIFO is flushed and the descriptor + * becomes valid once the control word is written last. */ - memcpy((void __force *)hw_desc, &desc->hw_desc, - sizeof(desc->hw_desc) - sizeof(u32)); + memcpy_toio(hw_desc, &desc->hw_desc, + offsetof(struct msgdma_extended_desc, control)); /* Write control word last to flush this descriptor into the FIFO */ mdev->idle = false; |