Re: [PATCH resend 11/15] drm/i915/dsi: Group MIPI_SEQ_BACKLIGHT_ON/OFF with panel_[en|dis]able_backlight

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 27 Feb 2017, Bob Paauwe <bob.j.paauwe@intel.com> wrote:
> On Sat, 25 Feb 2017 11:37:50 +0100
> Hans de Goede <hdegoede@redhat.com> wrote:
>
>> Hi,
>> 
>> On 24-02-17 18:00, Bob Paauwe wrote:
>> > On Mon, 20 Feb 2017 15:08:41 +0100
>> > Hans de Goede <hdegoede@redhat.com> wrote:
>> >  
>> >> Execute the MIPI_SEQ_BACKLIGHT_ON/OFF VBT sequences at the same time as
>> >> we call intel_panel_enable_backlight() / intel_panel_disable_backlight().
>> >>
>> >> Signed-off-by: Hans de Goede <hdegoede@redhat.com>  
>> >
>> > I'm not sure that the added comments are necessary.  Maybe if there was
>> > some explanation for why we're using two different mechanisms to
>> > enable/disable backlight instead.  
>> 
>> That assumes I know why there are 2 mechanisms of I have to guess it
>> is because on some boards only one of the mechanisms works, but that
>> is just a guess. Just calling the VBT sequence should be enough on
>> (most?) boards.
>> 
>> Regards,
>> 
>> Hans
>
> I don't think I can describe why we have two mechanisms so just
> dropping the comment would be my preference at this point.

I think they're mostly alternatives, and only one or the other gets
used, but since the VBT sequence is rather generic, I think it's
possible one controls the SoC side and the other the panel side.

> It may be that calling the intel_panel_enable_backlight() will make
> sure the sysfs entries are correct while the VBT sequence simply
> modifies the hardware. 
>
> Possibly a good solution would be to enhance the code that executes the
> VBT sequence to also call the intel_panel_enable_backlight(), but
> that's not something to change here.

Please leave it as it is.

BR,
Jani.

>
>> 
>> 
>> >
>> > Reviewed-by: Bob Paauwe <bob.j.paauwe@intel.com>
>> >  
>> >> ---
>> >>  drivers/gpu/drm/i915/intel_dsi.c | 6 ++++--
>> >>  1 file changed, 4 insertions(+), 2 deletions(-)
>> >>
>> >> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
>> >> index 8408f59..a8d0948 100644
>> >> --- a/drivers/gpu/drm/i915/intel_dsi.c
>> >> +++ b/drivers/gpu/drm/i915/intel_dsi.c
>> >> @@ -687,12 +687,13 @@ static void intel_dsi_pre_enable(struct intel_encoder *encoder,
>> >>  		msleep(100);
>> >>
>> >>  		intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_DISPLAY_ON);
>> >> -		intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_BACKLIGHT_ON);
>> >>
>> >>  		intel_dsi_port_enable(encoder);
>> >>  	}
>> >>
>> >> +	/* Enable backlight, both pwm and VBT */
>> >>  	intel_panel_enable_backlight() (intel_dsi->attached_connector);
>> >> +	intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_BACKLIGHT_ON);
>> >>  }
>> >>
>> >>  static void intel_dsi_enable_nop(struct intel_encoder *encoder,
>> >> @@ -718,6 +719,8 @@ static void intel_dsi_pre_disable(struct intel_encoder *encoder,
>> >>
>> >>  	DRM_DEBUG_KMS("\n");
>> >>
>> >> +	/* Disable backlight, both VBT and pwm */
>> >> +	intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_BACKLIGHT_OFF);
>> >>  	intel_panel_disable_backlight(intel_dsi->attached_connector);
>> >>
>> >>  	/*
>> >> @@ -762,7 +765,6 @@ static void intel_dsi_post_disable(struct intel_encoder *encoder,
>> >>  	 * if disable packets are sent before sending shutdown packet then in
>> >>  	 * some next enable sequence send turn on packet error is observed
>> >>  	 */
>> >> -	intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_BACKLIGHT_OFF);
>> >>  	intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_DISPLAY_OFF);
>> >>
>> >>  	/* Transition to LP-00 */  
>> >
>> >
>> >  

-- 
Jani Nikula, Intel Open Source Technology Center
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