| Message ID | 20171228082742.13415-1-robert.jarzmik@free.fr (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 28 Dec 2017, Robert Jarzmik wrote: > Currently the LCD display (TD035S) on the cm-x300 platform is broken and > remains blank. > > The TD0245S specification requires that the chipselect is toggled > between commands sent to the panel. This was also the purpose of the > former patch of commit f64dcac0b124 ("backlight: tdo24m: ensure chip > select changes between transfers"). > > Unfortunately, the "cs_change" field of a SPI transfer is > misleading. Its true meaning is that for a SPI message holding multiple > transfers, the chip select is toggled between each transfer, but for the > last transfer it remains asserted. > > In this driver, all the SPI messages contain exactly one transfer, which > means that each transfer is the last of its message, and as a > consequence the chip select is never toggled. > > Actually, there was a second bug hidding the first one, hence the > problem was not seen until v4.6. This problem was fixed by commit > a52db659c79c ("spi: pxa2xx: Fix cs_change management") for PXA based > boards. > > This fix makes the TD035S work again on a cm-x300 board. The same > applies to other PXA boards, ie. corgi and tosa. > > Fixes: a52db659c79c ("spi: pxa2xx: Fix cs_change management") Since this fixes an old kernel, I'm not going to apply it for -fixes. > Reported-by: Andrea Adami <andrea.adami@gmail.com> > Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> > Acked-by: Daniel Thompson <daniel.thompson@linaro.org> > --- > Since v1: added 2 other panels > Since v2: added Daniel's ack > --- > drivers/video/backlight/corgi_lcd.c | 2 +- > drivers/video/backlight/tdo24m.c | 2 +- > drivers/video/backlight/tosa_lcd.c | 2 +- > 3 files changed, 3 insertions(+), 3 deletions(-) Applied to -next, thanks.
diff --git a/drivers/video/backlight/corgi_lcd.c b/drivers/video/backlight/corgi_lcd.c index d7c239ea3d09..f5574060f9c8 100644 --- a/drivers/video/backlight/corgi_lcd.c +++ b/drivers/video/backlight/corgi_lcd.c @@ -177,7 +177,7 @@ static int corgi_ssp_lcdtg_send(struct corgi_lcd *lcd, int adrs, uint8_t data) struct spi_message msg; struct spi_transfer xfer = { .len = 1, - .cs_change = 1, + .cs_change = 0, .tx_buf = lcd->buf, }; diff --git a/drivers/video/backlight/tdo24m.c b/drivers/video/backlight/tdo24m.c index eab1f842f9c0..e4bd63e9db6b 100644 --- a/drivers/video/backlight/tdo24m.c +++ b/drivers/video/backlight/tdo24m.c @@ -369,7 +369,7 @@ static int tdo24m_probe(struct spi_device *spi) spi_message_init(m); - x->cs_change = 1; + x->cs_change = 0; x->tx_buf = &lcd->buf[0]; spi_message_add_tail(x, m); diff --git a/drivers/video/backlight/tosa_lcd.c b/drivers/video/backlight/tosa_lcd.c index 6a41ea92737a..4dc5ee8debeb 100644 --- a/drivers/video/backlight/tosa_lcd.c +++ b/drivers/video/backlight/tosa_lcd.c @@ -49,7 +49,7 @@ static int tosa_tg_send(struct spi_device *spi, int adrs, uint8_t data) struct spi_message msg; struct spi_transfer xfer = { .len = 1, - .cs_change = 1, + .cs_change = 0, .tx_buf = buf, };
Currently the LCD display (TD035S) on the cm-x300 platform is broken and remains blank. The TD0245S specification requires that the chipselect is toggled between commands sent to the panel. This was also the purpose of the former patch of commit f64dcac0b124 ("backlight: tdo24m: ensure chip select changes between transfers"). Unfortunately, the "cs_change" field of a SPI transfer is misleading. Its true meaning is that for a SPI message holding multiple transfers, the chip select is toggled between each transfer, but for the last transfer it remains asserted. In this driver, all the SPI messages contain exactly one transfer, which means that each transfer is the last of its message, and as a consequence the chip select is never toggled. Actually, there was a second bug hidding the first one, hence the problem was not seen until v4.6. This problem was fixed by commit a52db659c79c ("spi: pxa2xx: Fix cs_change management") for PXA based boards. This fix makes the TD035S work again on a cm-x300 board. The same applies to other PXA boards, ie. corgi and tosa. Fixes: a52db659c79c ("spi: pxa2xx: Fix cs_change management") Reported-by: Andrea Adami <andrea.adami@gmail.com> Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> Acked-by: Daniel Thompson <daniel.thompson@linaro.org> --- Since v1: added 2 other panels Since v2: added Daniel's ack --- drivers/video/backlight/corgi_lcd.c | 2 +- drivers/video/backlight/tdo24m.c | 2 +- drivers/video/backlight/tosa_lcd.c | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-)