[PATCH 6.6 004/299] dmaengine: apple-admac: Keep upper bits of REG_BUS_WIDTH

Greg Kroah-Hartman
2024-02-27T13:47:54Z

From: Hector Martin <marcan@marcan.st>

[ Upstream commit 306f5df81fcc89b462fbeb9dbe26d9a8ad7c7582 ]

For RX channels, REG_BUS_WIDTH seems to default to a value of 0xf00, and
macOS preserves the upper bits when setting the configuration in the
lower ones. If we reset the upper bits to 0, this causes framing errors
on suspend/resume (the data stream "tears" and channels get swapped
around). Keeping the upper bits untouched, like the macOS driver does,
fixes this issue.

Signed-off-by: Hector Martin <marcan@marcan.st>
Reviewed-by: Martin Povišer <povik+lin@cutebit.org>
Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
Link: https://lore.kernel.org/r/20231029170704.82238-1-povik+lin@cutebit.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/dma/apple-admac.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/apple-admac.c b/drivers/dma/apple-admac.c
index 3af795635c5ce..356298e4dd22b 100644
--- a/drivers/dma/apple-admac.c
+++ b/drivers/dma/apple-admac.c
@@ -57,6 +57,8 @@

#define REG_BUS_WIDTH(ch) (0x8040 + (ch) * 0x200)

+#define BUS_WIDTH_WORD_SIZE GENMASK(3, 0)
+#define BUS_WIDTH_FRAME_SIZE GENMASK(7, 4)
#define BUS_WIDTH_8BIT 0x00
#define BUS_WIDTH_16BIT 0x01
#define BUS_WIDTH_32BIT 0x02
@@ -740,7 +742,8 @@ static int admac_device_config(struct dma_chan *chan,
struct admac_data *ad = adchan->host;
bool is_tx = admac_chan_direction(adchan->no) == DMA_MEM_TO_DEV;
int wordsize = 0;
- u32 bus_width = 0;
+ u32 bus_width = readl_relaxed(ad->base + REG_BUS_WIDTH(adchan->no)) &
+ ~(BUS_WIDTH_WORD_SIZE | BUS_WIDTH_FRAME_SIZE);

switch (is_tx ? config->dst_addr_width : config->src_addr_width) {
case DMA_SLAVE_BUSWIDTH_1_BYTE:
--
2.43.0