[PATCH 1/3] backlight: tdo24m: fix the spi cs between transfers

[PATCH 1/3] backlight: tdo24m: fix the spi cs between transfers

[Robert Jarzmik]

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.

This fix makes the TD035S work again on a cm-x300 board.

Fixes: f64dcac0b124 ("backlight: tdo24m: ensure chip select changes
       between transfers")
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
---
 drivers/video/backlight/tdo24m.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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);
 
-- 
2.11.0

[PATCH 2/3] backlight: tdo24m: add the reset line gpio

[Robert Jarzmik]

The Toppoly panels have a global reset line. Add an optional gpio
control for this line, for platforms which have the ability to drive it.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
---
 drivers/video/backlight/tdo24m.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/video/backlight/tdo24m.c b/drivers/video/backlight/tdo24m.c
index e4bd63e9db6b..e4b2dfabf192 100644
--- a/drivers/video/backlight/tdo24m.c
+++ b/drivers/video/backlight/tdo24m.c
@@ -10,6 +10,7 @@
  */
 
 #include <linux/module.h>
+#include <linux/gpio/consumer.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/device.h>
@@ -32,6 +33,7 @@ struct tdo24m {
 	struct spi_message	msg;
 	struct spi_transfer	xfer;
 	uint8_t			*buf;
+	struct gpio_desc	*xres;
 
 	int (*adj_mode)(struct tdo24m *lcd, int mode);
 	int color_invert;
@@ -364,6 +366,7 @@ static int tdo24m_probe(struct spi_device *spi)
 	if (lcd->buf = NULL)
 		return -ENOMEM;
 
+	lcd->xres = devm_gpiod_get(&spi->dev, "reset", GPIOD_OUT_LOW);
 	m = &lcd->msg;
 	x = &lcd->xfer;
 
-- 
2.11.0

[PATCH 3/3] backlight: tdo24m: add model and status sysfs entries

[Robert Jarzmik]

Add entries to query the panel ASIC to acquire the model number and the
status field. This comes in handy to check that the SPI connection is
functional and that the panel's firmware is alive.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
---
 drivers/video/backlight/tdo24m.c | 73 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/drivers/video/backlight/tdo24m.c b/drivers/video/backlight/tdo24m.c
index e4b2dfabf192..113c28c2145a 100644
--- a/drivers/video/backlight/tdo24m.c
+++ b/drivers/video/backlight/tdo24m.c
@@ -22,7 +22,7 @@
 
 #define POWER_IS_ON(pwr)	((pwr) <= FB_BLANK_NORMAL)
 
-#define TDO24M_SPI_BUFF_SIZE	(4)
+#define TDO24M_SPI_BUFF_SIZE	(6)
 #define MODE_QVGA	0
 #define MODE_VGA	1
 
@@ -33,6 +33,7 @@ struct tdo24m {
 	struct spi_message	msg;
 	struct spi_transfer	xfer;
 	uint8_t			*buf;
+	uint8_t			*rx_buf;
 	struct gpio_desc	*xres;
 
 	int (*adj_mode)(struct tdo24m *lcd, int mode);
@@ -219,6 +220,30 @@ static int tdo24m_writes(struct tdo24m *lcd, const uint32_t *array)
 	return err;
 }
 
+static int tdo24m_read_command(struct tdo24m *lcd, unsigned char cmd,
+			       unsigned int *id)
+{
+	struct spi_transfer *x = &lcd->xfer;
+	int err = 0, i;
+
+	lcd->buf[0] = cmd >> 1;
+	lcd->buf[1] = (cmd & 0x01) << 7;
+	lcd->buf[2] = 0;
+	lcd->buf[3] = 0;
+	lcd->buf[4] = 0;
+
+	x->len = 6;
+	err = spi_sync(lcd->spi_dev, &lcd->msg);
+
+	for (i = 0; i < sizeof(lcd->rx_buf) - 2; i++)
+		lcd->rx_buf[i] = (lcd->rx_buf[i + 1] << 2) |
+			(lcd->rx_buf[i + 2] >> 6);
+	*id = (lcd->rx_buf[0] << 24) | (lcd->rx_buf[1] << 16) |
+		(lcd->rx_buf[2] << 8) | lcd->rx_buf[3];
+
+	return err;
+}
+
 static int tdo24m_adj_mode(struct tdo24m *lcd, int mode)
 {
 	switch (mode) {
@@ -327,6 +352,43 @@ static int tdo24m_set_mode(struct lcd_device *ld, struct fb_videomode *m)
 	return lcd->adj_mode(lcd, mode);
 }
 
+static ssize_t tdo24m_model_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct tdo24m *lcd = dev_get_drvdata(dev);
+	uint32_t data;
+	int err;
+
+	err = tdo24m_read_command(lcd, 0x04, &data);
+	if (!err)
+		return snprintf(buf, PAGE_SIZE, "0x%06x\n", data >> 8);
+
+	return err;
+}
+static DEVICE_ATTR_RO(tdo24m_model);
+
+static ssize_t tdo24m_status_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct tdo24m *lcd = dev_get_drvdata(dev);
+	uint32_t data;
+	int err;
+
+	err = tdo24m_read_command(lcd, 0x09, &data);
+	if (!err)
+		return snprintf(buf, PAGE_SIZE, "0x%08x\n", data);
+
+	return err;
+}
+static DEVICE_ATTR_RO(tdo24m_status);
+
+static struct attribute *tdo24m_attrs[] = {
+	&dev_attr_tdo24m_model.attr,
+	&dev_attr_tdo24m_status.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(tdo24m);
+
 static struct lcd_ops tdo24m_ops = {
 	.get_power	= tdo24m_get_power,
 	.set_power	= tdo24m_set_power,
@@ -365,6 +427,9 @@ static int tdo24m_probe(struct spi_device *spi)
 	lcd->buf = devm_kzalloc(&spi->dev, TDO24M_SPI_BUFF_SIZE, GFP_KERNEL);
 	if (lcd->buf = NULL)
 		return -ENOMEM;
+	lcd->rx_buf = devm_kzalloc(&spi->dev, TDO24M_SPI_BUFF_SIZE, GFP_KERNEL);
+	if (lcd->rx_buf = NULL)
+		return -ENOMEM;
 
 	lcd->xres = devm_gpiod_get(&spi->dev, "reset", GPIOD_OUT_LOW);
 	m = &lcd->msg;
@@ -374,6 +439,7 @@ static int tdo24m_probe(struct spi_device *spi)
 
 	x->cs_change = 0;
 	x->tx_buf = &lcd->buf[0];
+	x->rx_buf = &lcd->rx_buf[0];
 	spi_message_add_tail(x, m);
 
 	switch (model) {
@@ -396,6 +462,11 @@ static int tdo24m_probe(struct spi_device *spi)
 		return PTR_ERR(lcd->lcd_dev);
 
 	spi_set_drvdata(spi, lcd);
+
+	err = devm_device_add_groups(&spi->dev, tdo24m_groups);
+	if (err)
+		return err;
+
 	err = tdo24m_power(lcd, FB_BLANK_UNBLANK);
 	if (err)
 		return err;
-- 
2.11.0

Re: [PATCH 1/3] backlight: tdo24m: fix the spi cs between transfers

[Daniel Thompson]

On 06/10/17 20:58, 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.
> 
> This fix makes the TD035S work again on a cm-x300 board.
> 
> Fixes: f64dcac0b124 ("backlight: tdo24m: ensure chip select changes
>         between transfers")
> Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>

I'm a tiny bit worried about see-saw bug fixing here but nevertheless 
this change looks correct to me.

Mike's change was eight years ago and it is reasonable to hope that the 
patch was really just working around a (hopefully long fixed) bug in the 
SPI driver!


Acked-by: Daniel Thompson <daniel.thompson@linaro.org>


> ---
>   drivers/video/backlight/tdo24m.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> 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);
>   
> 

Re: [PATCH 1/3] backlight: tdo24m: fix the spi cs between transfers

[Robert Jarzmik]

Daniel Thompson <daniel.thompson@linaro.org> writes:

> On 06/10/17 20:58, Robert Jarzmik wrote:
>
> I'm a tiny bit worried about see-saw bug fixing here but nevertheless this
> change looks correct to me.
>
> Mike's change was eight years ago and it is reasonable to hope that the patch
> was really just working around a (hopefully long fixed) bug in the SPI driver!
Actually I think it's the case.
And the driver bug fix is here :
  a52db659c79c ("spi: pxa2xx: Fix cs_change management")

And please don't apply this as there are 2 other LCDs which are affected by the
same issue and reported by Andrea, for which I had not correlated the issue
until yesterday, so I'll have to respin this 2 others files, namely :
 - drivers/video/backlight/corgi_lcd.c.
 - drivers/video/backlight/tosa_lcd.c.

There 2 other candidates I won't touch as they are not under my maintainance,
and I have no way to test them :
 - ili922x.c
 - ltv350qv.c

> Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Thanks, but there will be a v2 with exactly the same fix in 3 files.

Cheers.

--
Robert