Re: [PATCH RESEND 4/7] drm/i915/dsi: run power on/off sequences in panel prepare/unprepare hooks

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Jun 13, 2016 at 01:22:15PM +0300, Jani Nikula wrote:
> Based on the documentation alone, it's anyone's guess when exactly we
> should be running these sequences. Add them where it feels logical. The
> drm panel hooks don't currently offer us more granularity anyway.
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dsi_panel_vbt.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> index 7dd850760c4d..e0337a82a6b4 100644
> --- a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> +++ b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> @@ -459,6 +459,7 @@ static void generic_exec_sequence(struct drm_panel *panel, enum mipi_seq seq_id)
>  static int vbt_panel_prepare(struct drm_panel *panel)
>  {
>  	generic_exec_sequence(panel, MIPI_SEQ_ASSERT_RESET);
> +	generic_exec_sequence(panel, MIPI_SEQ_POWER_ON);
>  	generic_exec_sequence(panel, MIPI_SEQ_INIT_OTP);

Indeed, our spec is useless here :(

What would make sense to me is

assert reset // just in case it wasn't already asserted
power on
deassert reset
init otp

>  
>  	return 0;
> @@ -466,6 +467,7 @@ static int vbt_panel_prepare(struct drm_panel *panel)
>  
>  static int vbt_panel_unprepare(struct drm_panel *panel)
>  {
> +	generic_exec_sequence(panel, MIPI_SEQ_POWER_OFF);
>  	generic_exec_sequence(panel, MIPI_SEQ_DEASSERT_RESET);

And here I'd do 

assert reset
power off

and nothing more.

This would also seem to agree with a few panel specs I have lying
around.

But of course I could be mistaken, eg. if the panel on/off sequeneces
themselves would had some kind of magic reset (de)assert already inside
them. Nothing in the spec suggests this though.

>  
>  	return 0;
> -- 
> 2.1.4
> 
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-- 
Ville Syrjälä
Intel OTC
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