Hi Noralf,
Le dim. 5 juil. 2020 à 17:58, Noralf Trønnes <noralf@xxxxxxxxxxx> a
écrit :
Den 03.07.2020 16.13, skrev Paul Cercueil:
The function mipi_dbi_spi1_transfer() will transfer its payload as
9-bit
data, the 9th (MSB) bit being the data/command bit. In order to do
that,
it unpacks the 8-bit values into 16-bit values, then sets the 9th
bit if
the byte corresponds to data, clears it otherwise. The 7 MSB are
padding. The array of now 16-bit values is then passed to the SPI
core
for transfer.
This function was broken since its introduction, as the length of
the
SPI transfer was set to the payload size before its conversion, but
the
payload doubled in size due to the 8-bit -> 16-bit conversion.
Fixes: 02dd95fe3169 ("drm/tinydrm: Add MIPI DBI support")
Cc: <stable@xxxxxxxxxxxxxxx> # 4.10
The code was moved to drm_mipi_dbi.c in 5.4 so this patch won't apply
before that.
I believe I can submit a patch for pre-5.4 too.
Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
---
Thanks for fixing this, clearly I didn't test this. Probably because
the
aux spi ip block on the Raspberry Pi that can do 9 bit didn't have a
driver at the time. Did you actually test this or was it spotted
reading
the code?
I did test it on hardware, yes - that's how I spotted the bug.
-Paul
Reviewed-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
drivers/gpu/drm/drm_mipi_dbi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_mipi_dbi.c
b/drivers/gpu/drm/drm_mipi_dbi.c
index bb27c82757f1..bf7888ad9ad4 100644
--- a/drivers/gpu/drm/drm_mipi_dbi.c
+++ b/drivers/gpu/drm/drm_mipi_dbi.c
@@ -923,7 +923,7 @@ static int mipi_dbi_spi1_transfer(struct
mipi_dbi *dbi, int dc,
}
}
- tr.len = chunk;
+ tr.len = chunk * 2;
len -= chunk;
ret = spi_sync(spi, &m);
