| Message ID | 20200703141341.1266263-1-paul@crapouillou.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/dbi: Fix SPI Type 1 (9-bit) transfer | expand |
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); >>
Hi Paul. On Fri, Jul 03, 2020 at 04:23:57PM +0200, Sam Ravnborg wrote: > On Fri, Jul 03, 2020 at 04:13:41PM +0200, Paul Cercueil wrote: > > 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 > > Signed-off-by: Paul Cercueil <paul@crapouillou.net> > > As discussed on irc this looks correct to me too. > > Reviewed-by: Sam Ravnborg <sam@ravnborg.org> > > > I will apply later, but let's wait and see if Noralf or others > have any feedback first. I finally went back to this patch, I missed it yesterday. Applied to drm-misc-fixes with a stable 5.4+ tag. Sam > > --- > > 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); > > -- > > 2.27.0 > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel
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);
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 Signed-off-by: Paul Cercueil <paul@crapouillou.net> --- drivers/gpu/drm/drm_mipi_dbi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)