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backlight: tdo24m: Fix the SPI CS between transfers 

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 f64dcac0b1 ("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
a52db659c7 ("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: a52db659c7 ("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>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
This commit is contained in:
Robert Jarzmik 2017-12-28 09:27:41 +01:00 committed by Lee Jones
parent 12a9d3bb6a
commit 2023b0524a
3 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/video/backlight/corgi_lcd.c
View File

@ -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,
};

2
drivers/video/backlight/tdo24m.c
View File

@ -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);

2
drivers/video/backlight/tosa_lcd.c
View File

@ -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,
};