[PATCH 2/2] drm/dsi: Implement dcs backlight brightness

[Vinay Simha]

On Mon, Jun 6, 2016 at 1:07 PM, Jani Nikula <jani.nikula at linux.intel.com> wrote:
> On Thu, 02 Jun 2016, Vinay Simha BN <simhavcs at gmail.com> wrote:
>> Provide a small convenience wrapper that set/get the
>> backlight brightness control and creates the backlight
>> device for the panel interface
>
> To be pedantic, we should downplay "backlight" in the DSI DCS brightness
> control... there need not be a backlight, at all, for brightness control
> (see AMOLED).
but this jdi display and few other dsi display can be controlled by dcs commands

>
>> Cc: John Stultz <john.stultz at linaro.org>
>> Cc: Sumit Semwal <sumit.semwal at linaro.org>
>> Cc: Archit Taneja <archit.taneja at gmail.com>
>> Cc: Rob Clark <robdclark at gmail.com>
>> Signed-off-by: Vinay Simha BN <simhavcs at gmail.com>
>>
>> --
>> v1:
>>  *tested in nexus7 2nd gen.
>> ---
>>  drivers/gpu/drm/drm_mipi_dsi.c | 63 ++++++++++++++++++++++++++++++++++++++++++
>>  include/drm/drm_mipi_dsi.h     |  3 ++
>>  2 files changed, 66 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
>> index 2f0b85c..ac4521e 100644
>> --- a/drivers/gpu/drm/drm_mipi_dsi.c
>> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
>> @@ -1026,6 +1026,69 @@ int mipi_dsi_dcs_set_pixel_format(struct mipi_dsi_device *dsi, u8 format)
>>  }
>>  EXPORT_SYMBOL(mipi_dsi_dcs_set_pixel_format);
>>
>> +static int dsi_dcs_bl_get_brightness(struct backlight_device *bl)
>
> I'd rather see convenience helpers that are not tied to struct
> backlight_device. You can add a one-line wrapper on top that takes
> struct backlight_device pointer.
>
i need to move the backlight_ops, backlight struct in panel driver and need to
set/get brightness in drm_mipi_dsi.c
> While at it, please name the helpers according to the DCS command.
i will changes this to in v2 version
mipi_dsi_dcs_set_brightness
mipi_dsi_dcs_get_brightness
>
>> +{
>> +     struct mipi_dsi_device *dsi = bl_get_data(bl);
>> +     int ret;
>> +     u8 brightness;
>> +
>> +     dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
>> +
>> +     ret = mipi_dsi_dcs_read(dsi, MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
>> +                             &brightness, sizeof(brightness));
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     dsi->mode_flags |= MIPI_DSI_MODE_LPM;
>> +
>> +     return brightness;
>> +}
>> +
>> +static int dsi_dcs_bl_update_status(struct backlight_device *bl)
>> +{
>> +     struct mipi_dsi_device *dsi = bl_get_data(bl);
>> +     int ret;
>> +     u8 brightness = bl->props.brightness;
>> +
>> +     dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
>> +
>> +     ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
>> +                              &brightness, sizeof(brightness));
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     dsi->mode_flags |= MIPI_DSI_MODE_LPM;
>> +
>> +     return 0;
>> +}
>> +
>> +static const struct backlight_ops dsi_bl_ops = {
>> +     .update_status = dsi_dcs_bl_update_status,
>> +     .get_brightness = dsi_dcs_bl_get_brightness,
>> +};
>> +
>> +/**
>> + * drm_panel_create_dsi_backlight() - creates the backlight device for the panel
>> + * @dsi: DSI peripheral device
>> + *
>> + * @return a struct backlight on success, or an ERR_PTR on error
>> + */
>> +struct backlight_device
>> +             *drm_panel_create_dsi_backlight(struct mipi_dsi_device *dsi)
>> +{
>> +     struct device *dev = &dsi->dev;
>> +     struct backlight_properties props;
>> +
>> +     memset(&props, 0, sizeof(props));
>> +     props.type = BACKLIGHT_RAW;
>> +     props.brightness = 255;
>> +     props.max_brightness = 255;
>
> The DCS spec says the max is either 0xff or 0xffff depending on the
> implementation... this obviously affects the helpers as well.
>
> And how about the backlight bits in write_control_display? 8 bits
I just fear
> this is a simplistic view of brightness control on DSI, and this will
> grow hairy over time. I think I'd rather see generic DSI DCS brightness
> *helpers* in this file, and then *perhaps* a separate file for
> brightness control in general.
>
> BR,
> Jani.
>
>> +
>> +     return devm_backlight_device_register(dev, dev_name(dev), dev, dsi,
>> +                                           &dsi_bl_ops, &props);
>> +}
>> +EXPORT_SYMBOL(drm_panel_create_dsi_backlight);
>> +
>>  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 2788dbe..9dd6a97 100644
>> --- a/include/drm/drm_mipi_dsi.h
>> +++ b/include/drm/drm_mipi_dsi.h
>> @@ -12,6 +12,7 @@
>>  #ifndef __DRM_MIPI_DSI_H__
>>  #define __DRM_MIPI_DSI_H__
>>
>> +#include <linux/backlight.h>
>>  #include <linux/device.h>
>>
>>  struct mipi_dsi_host;
>> @@ -269,6 +270,8 @@ int mipi_dsi_dcs_set_tear_off(struct mipi_dsi_device *dsi);
>>  int mipi_dsi_dcs_set_tear_on(struct mipi_dsi_device *dsi,
>>                            enum mipi_dsi_dcs_tear_mode mode);
>>  int mipi_dsi_dcs_set_pixel_format(struct mipi_dsi_device *dsi, u8 format);
>> +struct backlight_device
>> +     *drm_panel_create_dsi_backlight(struct mipi_dsi_device *dsi);
>>
>>  /**
>>   * struct mipi_dsi_driver - DSI driver
>
> --
> Jani Nikula, Intel Open Source Technology Center



-- 
Regards,

Vinay Simha.B.N.