Hi Noralf,
Le dim. 5 juil. 2020 à 17:58, Noralf Trønnes noralf@tronnes.org 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@vger.kernel.org # 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@crapouillou.net
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@tronnes.org
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);