[Intel-gfx] [PATCH v2] drm/i915/dsi: transmit brightness command in HS state

[Jani Nikula]

On Tue, 09 Nov 2021, William Tseng <william.tseng at intel.com> wrote:
> In Video Mode, if DSI transcoder is set to transmit packets
> in LP Escape mode, screen flickering would be obseved when
> brightness commands are continuously and quickly transmitted
> to a panel.
>
> The problem may be resolved by changing the mode to transmit
> packets from Low Power to HS.
>
> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Vandita Kulkarni <vandita.kulkarni at intel.com>
> Cc: Lee Shawn C <shawn.c.lee at intel.com>
> Cc: Cooper Chiou <cooper.chiou at intel.com>
> Signed-off-by: William Tseng <william.tseng at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c b/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
> index f61ed82e8867..2f788cb0f597 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
> @@ -81,8 +81,10 @@ static void dcs_set_backlight(const struct drm_connector_state *conn_state, u32
>  
>  	for_each_dsi_port(port, intel_dsi->dcs_backlight_ports) {
>  		dsi_device = intel_dsi->dsi_hosts[port]->device;
> +		dsi_device->mode_flags &= ~MIPI_DSI_MODE_LPM;
>  		mipi_dsi_dcs_write(dsi_device, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
>  				   &data, len);
> +		dsi_device->mode_flags |= MIPI_DSI_MODE_LPM;

Ah, but this doesn't *restore* the flags, it forces MIPI_DSI_MODE_LPM!

BR,
Jani.

>  	}
>  }

-- 
Jani Nikula, Intel Open Source Graphics Center