diff options
| author | Kartik Rajput <kkartik@nvidia.com> | 2026-02-25 12:29:14 +0530 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-03-12 15:06:39 +0100 |
| commit | d925538446d3f80e03a91a9ef7da34104a75df4d (patch) | |
| tree | eaa007da6ac5d8c0a5116f66123e2db8a3dce3e5 | |
| parent | a2abd18e316ee2442631f0a60896b49dd8e9a80c (diff) | |
serial: amba-pl011: Respect DMA controller's copy_align requirement
Some DMA controllers require transfer lengths to be aligned to a
specific boundary. For example, the Tegra GPC DMA requires 4-byte
(word) aligned transfers and will reject unaligned lengths.
Align the TX DMA buffer length down to the DMA controller's copy_align
boundary before submitting the transfer. Any remaining unaligned bytes
will be transmitted via PIO on subsequent calls, which is the existing
fallback behavior when DMA is not used.
Signed-off-by: Kartik Rajput <kkartik@nvidia.com>
Link: https://patch.msgid.link/20260225065915.341522-5-kkartik@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/serial/amba-pl011.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index b604274c1791..028e37ad8d79 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -649,6 +649,15 @@ static int pl011_dma_tx_refill(struct uart_amba_port *uap) count = PL011_DMA_BUFFER_SIZE; count = kfifo_out_peek(&tport->xmit_fifo, dmatx->buf, count); + + /* + * Align the TX buffer length to the DMA controller's copy_align + * requirements. Some DMA controllers (e.g., Tegra GPC DMA) require + * word-aligned transfers. Unaligned bytes will be sent via PIO. + */ + if (chan->device->copy_align) + count = ALIGN_DOWN(count, 1 << chan->device->copy_align); + dmatx->len = count; dmatx->dma = dma_map_single(dma_dev->dev, dmatx->buf, count, DMA_TO_DEVICE); |