[RFC PATCH v2 0/2] drm/dsi-mipi: 16-bit Brightness Endianness Fix

[RFC PATCH v2 0/2] drm/dsi-mipi: 16-bit Brightness Endianness Fix

[Richard Acayan]

Changes since v1:
 - move 16-bit brightness handling to new functions and revert API
   change (1/2)
 - remove Change-Id in compliance with checkpatch.pl (1/2)
 - separate panel driver changes (2/2)

This series adds proper support for 16-bit MIPI DSI brightness and
cleans up existing panel drivers.

I cannot test the SOFEF00 change, although I tested an equivalent change
to an external S6E3FA7 driver generated with the same generator. Both
setting and getting works on S6E3FA7.

Daniel Mentz (1):
  drm/dsi-mipi: Fix byte order of DCS set/get brightness

Richard Acayan (1):
  drm/panel: sofef00: Use 16-bit panel brightness

 drivers/gpu/drm/drm_mipi_dsi.c                | 52 +++++++++++++++++++
 drivers/gpu/drm/panel/panel-samsung-sofef00.c |  9 +---
 include/drm/drm_mipi_dsi.h                    |  4 ++
 3 files changed, 58 insertions(+), 7 deletions(-)

-- 
2.39.0

[RFC PATCH v2 1/2] drm/dsi-mipi: Fix byte order of DCS set/get brightness

[Richard Acayan]

From: Daniel Mentz <danielmentz@google.com>

The MIPI DCS specification demands that brightness values are sent in
big endian byte order. It also states that one parameter (i.e. one byte)
shall be sent/received for 8 bit wide values, and two parameters shall
be used for values that are between 9 and 16 bits wide.

Fixes: 1a9d759331b8 ("drm/dsi: Implement DCS set/get display brightness")
Signed-off-by: Daniel Mentz <danielmentz@google.com>
Change-Id: I24306e21ec6a5ff48ea121d977419a81d5b44152
Link: https://android.googlesource.com/kernel/msm/+/754affd62d0ee268c686c53169b1dbb7deac8550
[richard: fix 16-bit brightness_get]
[richard: use separate functions instead of switch/case]
Signed-off-by: Richard Acayan <mailingradian@gmail.com>
---
 drivers/gpu/drm/drm_mipi_dsi.c | 52 ++++++++++++++++++++++++++++++++++
 include/drm/drm_mipi_dsi.h     |  4 +++
 2 files changed, 56 insertions(+)

diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index 497ef4b6a90a..4bc15fbd009d 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -1224,6 +1224,58 @@ int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
 }
 EXPORT_SYMBOL(mipi_dsi_dcs_get_display_brightness);
 
+/**
+ * mipi_dsi_dcs_set_display_brightness_large() - sets the 16-bit brightness value
+ *    of the display
+ * @dsi: DSI peripheral device
+ * @brightness: brightness value
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int mipi_dsi_dcs_set_display_brightness_large(struct mipi_dsi_device *dsi,
+					     u16 brightness)
+{
+	u8 payload[2] = { brightness >> 8, brightness & 0xff };
+	ssize_t err;
+
+	err = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
+				 payload, sizeof(payload));
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dsi_dcs_set_display_brightness_large);
+
+/**
+ * mipi_dsi_dcs_get_display_brightness_large() - gets the current 16-bit
+ *    brightness value of the display
+ * @dsi: DSI peripheral device
+ * @brightness: brightness value
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
+					     u16 *brightness)
+{
+	u8 brightness_be[2];
+	ssize_t err;
+
+	err = mipi_dsi_dcs_read(dsi, MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
+				brightness_be, sizeof(brightness_be));
+	if (err <= 0) {
+		if (err == 0)
+			err = -ENODATA;
+
+		return err;
+	}
+
+	*brightness = (brightness_be[0] << 8) | brightness_be[1];
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dsi_dcs_get_display_brightness_large);
+
 static int mipi_dsi_drv_probe(struct device *dev)
 {
 	struct mipi_dsi_driver *drv = to_mipi_dsi_driver(dev->driver);
diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 4f503d99f668..16f30975b22b 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -296,6 +296,10 @@ int mipi_dsi_dcs_set_display_brightness(struct mipi_dsi_device *dsi,
 					u16 brightness);
 int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
 					u16 *brightness);
+int mipi_dsi_dcs_set_display_brightness_large(struct mipi_dsi_device *dsi,
+					     u16 brightness);
+int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
+					     u16 *brightness);
 
 /**
  * mipi_dsi_generic_write_seq - transmit data using a generic write packet
-- 
2.39.0

Re: [RFC PATCH v2 1/2] drm/dsi-mipi: Fix byte order of DCS set/get brightness

[Richard Acayan]

On Fri, Jan 13, 2023 at 08:00:05PM -0500, Richard Acayan wrote:
> From: Daniel Mentz <danielmentz@google.com>
> 
> The MIPI DCS specification demands that brightness values are sent in
> big endian byte order. It also states that one parameter (i.e. one byte)
> shall be sent/received for 8 bit wide values, and two parameters shall
> be used for values that are between 9 and 16 bits wide.
> 
> Fixes: 1a9d759331b8 ("drm/dsi: Implement DCS set/get display brightness")
> Signed-off-by: Daniel Mentz <danielmentz@google.com>
> Change-Id: I24306e21ec6a5ff48ea121d977419a81d5b44152
I need to check which local commits I'm actually emailing...

This line will be removed in v3.

> Link: https://android.googlesource.com/kernel/msm/+/754affd62d0ee268c686c53169b1dbb7deac8550
> [richard: fix 16-bit brightness_get]
> [richard: use separate functions instead of switch/case]
> Signed-off-by: Richard Acayan <mailingradian@gmail.com>
> ---
>  drivers/gpu/drm/drm_mipi_dsi.c | 52 ++++++++++++++++++++++++++++++++++
>  include/drm/drm_mipi_dsi.h     |  4 +++
>  2 files changed, 56 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> index 497ef4b6a90a..4bc15fbd009d 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -1224,6 +1224,58 @@ int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
>  }
>  EXPORT_SYMBOL(mipi_dsi_dcs_get_display_brightness);
>  
> +/**
> + * mipi_dsi_dcs_set_display_brightness_large() - sets the 16-bit brightness value
> + *    of the display
> + * @dsi: DSI peripheral device
> + * @brightness: brightness value
> + *
> + * Return: 0 on success or a negative error code on failure.
> + */
> +int mipi_dsi_dcs_set_display_brightness_large(struct mipi_dsi_device *dsi,
> +					     u16 brightness)
> +{
> +	u8 payload[2] = { brightness >> 8, brightness & 0xff };
> +	ssize_t err;
> +
> +	err = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
> +				 payload, sizeof(payload));
> +	if (err < 0)
> +		return err;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(mipi_dsi_dcs_set_display_brightness_large);
> +
> +/**
> + * mipi_dsi_dcs_get_display_brightness_large() - gets the current 16-bit
> + *    brightness value of the display
> + * @dsi: DSI peripheral device
> + * @brightness: brightness value
> + *
> + * Return: 0 on success or a negative error code on failure.
> + */
> +int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
> +					     u16 *brightness)
> +{
> +	u8 brightness_be[2];
> +	ssize_t err;
> +
> +	err = mipi_dsi_dcs_read(dsi, MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
> +				brightness_be, sizeof(brightness_be));
> +	if (err <= 0) {
> +		if (err == 0)
> +			err = -ENODATA;
> +
> +		return err;
> +	}
> +
> +	*brightness = (brightness_be[0] << 8) | brightness_be[1];
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(mipi_dsi_dcs_get_display_brightness_large);
> +
>  static int mipi_dsi_drv_probe(struct device *dev)
>  {
>  	struct mipi_dsi_driver *drv = to_mipi_dsi_driver(dev->driver);
> diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
> index 4f503d99f668..16f30975b22b 100644
> --- a/include/drm/drm_mipi_dsi.h
> +++ b/include/drm/drm_mipi_dsi.h
> @@ -296,6 +296,10 @@ int mipi_dsi_dcs_set_display_brightness(struct mipi_dsi_device *dsi,
>  					u16 brightness);
>  int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
>  					u16 *brightness);
> +int mipi_dsi_dcs_set_display_brightness_large(struct mipi_dsi_device *dsi,
> +					     u16 brightness);
> +int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
> +					     u16 *brightness);
>  
>  /**
>   * mipi_dsi_generic_write_seq - transmit data using a generic write packet
> -- 
> 2.39.0
> 

[RFC PATCH v2 2/2] drm/panel: sofef00: Use 16-bit panel brightness

[Richard Acayan]

These panels communicate brightness in big endian. This is not a quirk
of the panels themselves, but rather, a part of the MIPI standard. Use
the new mipi_dsi_dcs_set_display_brightness_wide() function that
properly handles 16-bit brightness instead of doing special processing
of the brightness values.

Signed-off-by: Richard Acayan <mailingradian@gmail.com>
---
 drivers/gpu/drm/panel/panel-samsung-sofef00.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-samsung-sofef00.c b/drivers/gpu/drm/panel/panel-samsung-sofef00.c
index 1a0d24595faa..014fe350bc59 100644
--- a/drivers/gpu/drm/panel/panel-samsung-sofef00.c
+++ b/drivers/gpu/drm/panel/panel-samsung-sofef00.c
@@ -10,7 +10,6 @@
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/regulator/consumer.h>
-#include <linux/swab.h>
 #include <linux/backlight.h>
 
 #include <video/mipi_display.h>
@@ -221,13 +220,9 @@ static int sofef00_panel_bl_update_status(struct backlight_device *bl)
 {
 	struct mipi_dsi_device *dsi = bl_get_data(bl);
 	int err;
-	u16 brightness;
+	u16 brightness = (u16)backlight_get_brightness(bl);
 
-	brightness = (u16)backlight_get_brightness(bl);
-	// This panel needs the high and low bytes swapped for the brightness value
-	brightness = __swab16(brightness);
-
-	err = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
+	err = mipi_dsi_dcs_set_display_brightness_large(dsi, brightness);
 	if (err < 0)
 		return err;
 
-- 
2.39.0

Re: [RFC PATCH v2 2/2] drm/panel: sofef00: Use 16-bit panel brightness

[Caleb Connolly]

On 14/01/2023 01:00, Richard Acayan wrote:
> These panels communicate brightness in big endian. This is not a quirk
> of the panels themselves, but rather, a part of the MIPI standard. Use
> the new mipi_dsi_dcs_set_display_brightness_wide() function that
> properly handles 16-bit brightness instead of doing special processing
> of the brightness values.
>
> Signed-off-by: Richard Acayan <mailingradian@gmail.com>

Awesome! Thanks for this series, glad to know this isn't a weird panel
quirk aha.

This works fine on the OnePlus 6 (the user of this panel), so for both
patches:

Tested-by: Caleb Connolly <caleb@connolly.tech>
> ---
>  drivers/gpu/drm/panel/panel-samsung-sofef00.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/panel/panel-samsung-sofef00.c b/drivers/gpu/drm/panel/panel-samsung-sofef00.c
> index 1a0d24595faa..014fe350bc59 100644
> --- a/drivers/gpu/drm/panel/panel-samsung-sofef00.c
> +++ b/drivers/gpu/drm/panel/panel-samsung-sofef00.c
> @@ -10,7 +10,6 @@
>  #include <linux/of.h>
>  #include <linux/of_device.h>
>  #include <linux/regulator/consumer.h>
> -#include <linux/swab.h>
>  #include <linux/backlight.h>
>
>  #include <video/mipi_display.h>
> @@ -221,13 +220,9 @@ static int sofef00_panel_bl_update_status(struct backlight_device *bl)
>  {
>  	struct mipi_dsi_device *dsi = bl_get_data(bl);
>  	int err;
> -	u16 brightness;
> +	u16 brightness = (u16)backlight_get_brightness(bl);
>
> -	brightness = (u16)backlight_get_brightness(bl);
> -	// This panel needs the high and low bytes swapped for the brightness value
> -	brightness = __swab16(brightness);
> -
> -	err = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
> +	err = mipi_dsi_dcs_set_display_brightness_large(dsi, brightness);
>  	if (err < 0)
>  		return err;
>
> --
> 2.39.0
>

--
Kind Regards,
Caleb