Re: [Intel-gfx] [PATCH] drm/i915/dsi: Always use unconditional msleep() for the panel_on_delay

[Hans de Goede <hdegoede@redhat.com>]

Hi Ville,

On 4/24/23 20:34, Ville Syrjälä wrote:
> On Sat, Apr 22, 2023 at 08:43:59PM +0200, Hans de Goede wrote:
>> The intel_dsi_msleep() helper skips sleeping if the MIPI-sequences have
>> a version of 3 or newer and the panel is in vid-mode.
>>
>> This is based on the big comment around line 730 which starts with
>> "Panel enable/disable sequences from the VBT spec.", where
>> the "v3 video mode seq" column does not have any wait t# entries.
>>
>> Commit 6fdb335f1c9c ("drm/i915/dsi: Use unconditional msleep for
>> the panel_on_delay when there is no reset-deassert MIPI-sequence")
>> switched to a direct msleep() instead of intel_dsi_msleep()
>> when there is no MIPI_SEQ_DEASSERT_RESET sequence, to fix
>> the panel on an Acer Aspire Switch 10 E SW3-016 not turning on.
>>
>> This was done under the assumption that when there is a v3
>> MIPI_SEQ_DEASSERT_RESET sequence it will take care of any
>> necessary delays.
>>
>> On the Nextbook Ares 8A (a Cherry Trail device like the Acer SW3-016)
>> there is a MIPI_SEQ_DEASSERT_RESET sequence, yet panel_on_delay
>> must still be honored otherwise the panel will not turn on.
>>
>> Switch to always using an unconditional msleep() for
>> the panel_on_delay instead of making this depend on
>> the presence of a MIPI_SEQ_DEASSERT_RESET sequence.
> 
> I just checked what Windows does, and at least for icl+ it
> always waits for the panel power delays regardless of what
> the VBT MIPI sequences are doing.
> 
> So I suspect we should just get rid of intel_dsi_msleep()
> entirely and do what the power sequencing delays tell us.
> Anything else is untested territory. If the VBT actually
> wanted us to skip the delays then it should really be
> setting them to zero.

So I checked and there are only 4 (before this patch) /
3 (after this patch) callers of intel_dsi_msleep().

So just getting rid of it entirely sounds good to me.

Shall I prepare a v2 patch which does this ?

Regards,

Hans





>> Fixes: 6fdb335f1c9c ("drm/i915/dsi: Use unconditional msleep for the panel_on_delay when there is no reset-deassert MIPI-sequence")
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>  drivers/gpu/drm/i915/display/vlv_dsi.c | 18 +++---------------
>>  1 file changed, 3 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/vlv_dsi.c b/drivers/gpu/drm/i915/display/vlv_dsi.c
>> index a6d6d8b33f3f..1b87f8f5f7fd 100644
>> --- a/drivers/gpu/drm/i915/display/vlv_dsi.c
>> +++ b/drivers/gpu/drm/i915/display/vlv_dsi.c
>> @@ -788,7 +788,6 @@ static void intel_dsi_pre_enable(struct intel_atomic_state *state,
>>  {
>>  	struct intel_dsi *intel_dsi = enc_to_intel_dsi(encoder);
>>  	struct intel_crtc *crtc = to_intel_crtc(pipe_config->uapi.crtc);
>> -	struct intel_connector *connector = to_intel_connector(conn_state->connector);
>>  	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
>>  	enum pipe pipe = crtc->pipe;
>>  	enum port port;
>> @@ -836,21 +835,10 @@ static void intel_dsi_pre_enable(struct intel_atomic_state *state,
>>  	if (!IS_GEMINILAKE(dev_priv))
>>  		intel_dsi_prepare(encoder, pipe_config);
>>  
>> +	/* Give the panel time to power-on and then deassert its reset */
>>  	intel_dsi_vbt_exec_sequence(intel_dsi, MIPI_SEQ_POWER_ON);
>> -
>> -	/*
>> -	 * Give the panel time to power-on and then deassert its reset.
>> -	 * Depending on the VBT MIPI sequences version the deassert-seq
>> -	 * may contain the necessary delay, intel_dsi_msleep() will skip
>> -	 * the delay in that case. If there is no deassert-seq, then an
>> -	 * unconditional msleep is used to give the panel time to power-on.
>> -	 */
>> -	if (connector->panel.vbt.dsi.sequence[MIPI_SEQ_DEASSERT_RESET]) {
>> -		intel_dsi_msleep(intel_dsi, intel_dsi->panel_on_delay);
>> -		intel_dsi_vbt_exec_sequence(intel_dsi, MIPI_SEQ_DEASSERT_RESET);
>> -	} else {
>> -		msleep(intel_dsi->panel_on_delay);
>> -	}
>> +	msleep(intel_dsi->panel_on_delay);
>> +	intel_dsi_vbt_exec_sequence(intel_dsi, MIPI_SEQ_DEASSERT_RESET);
>>  
>>  	if (IS_GEMINILAKE(dev_priv)) {
>>  		glk_cold_boot = glk_dsi_enable_io(encoder);
>> -- 
>> 2.39.2
>