linux-kernel - Re: [PATCH 3/5] drm/i915/dsi: Init panel-enable GPIO to low when the LCD is initially off

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Message-ID: <c7fe3911-be20-33dd-96c1-58eccd0f323f@redhat.com>
Date:   Mon, 16 Dec 2019 14:51:54 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Lee Jones <lee.jones@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-gpio@...r.kernel.org
Subject: Re: [PATCH 3/5] drm/i915/dsi: Init panel-enable GPIO to low when the
 LCD is initially off

Hi,

Thank you for the reviews.

On 16-12-2019 14:45, Ville Syrjälä wrote:
> On Sun, Dec 15, 2019 at 05:38:08PM +0100, Hans de Goede wrote:
>> When the LCD has not been turned on by the firmware/GOP, because e.g. the
>> device was booted with an external monitor connected over HDMI, we should
>> not turn on the panel-enable GPIO when we request it.
>>
>> Turning on the panel-enable GPIO when we request it, means we turn it on
>> too early in the init-sequence, which causes some panels to not correctly
>> light up.
>>
>> This commits adds a panel_is_on parameter to intel_dsi_vbt_gpio_init()
>> and makes intel_dsi_vbt_gpio_init() set the initial GPIO value accordingly.
>>
>> This fixes the panel not lighting up on a Thundersoft TST168 tablet when
>> booted with an external monitor connected over HDMI.
>>
>> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_dsi.h     | 2 +-
>>   drivers/gpu/drm/i915/display/intel_dsi_vbt.c | 7 +++----
>>   drivers/gpu/drm/i915/display/vlv_dsi.c       | 2 +-
>>   3 files changed, 5 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dsi.h b/drivers/gpu/drm/i915/display/intel_dsi.h
>> index de7e51cd3460..675771ea91aa 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dsi.h
>> +++ b/drivers/gpu/drm/i915/display/intel_dsi.h
>> @@ -203,7 +203,7 @@ void bxt_dsi_reset_clocks(struct intel_encoder *encoder, enum port port);
>>   
>>   /* intel_dsi_vbt.c */
>>   bool intel_dsi_vbt_init(struct intel_dsi *intel_dsi, u16 panel_id);
>> -void intel_dsi_vbt_gpio_init(struct intel_dsi *intel_dsi);
>> +void intel_dsi_vbt_gpio_init(struct intel_dsi *intel_dsi, bool panel_is_on);
>>   void intel_dsi_vbt_gpio_cleanup(struct intel_dsi *intel_dsi);
>>   void intel_dsi_vbt_exec_sequence(struct intel_dsi *intel_dsi,
>>   				 enum mipi_seq seq_id);
>> diff --git a/drivers/gpu/drm/i915/display/intel_dsi_vbt.c b/drivers/gpu/drm/i915/display/intel_dsi_vbt.c
>> index 5352e8c9eca5..027970348b22 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dsi_vbt.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dsi_vbt.c
>> @@ -688,17 +688,16 @@ bool intel_dsi_vbt_init(struct intel_dsi *intel_dsi, u16 panel_id)
>>    * On some BYT/CHT devs some sequences are incomplete and we need to manually
>>    * control some GPIOs.
>>    */
>> -void intel_dsi_vbt_gpio_init(struct intel_dsi *intel_dsi)
>> +void intel_dsi_vbt_gpio_init(struct intel_dsi *intel_dsi, bool panel_is_on)
>>   {
>>   	struct drm_device *dev = intel_dsi->base.base.dev;
>>   	struct drm_i915_private *dev_priv = to_i915(dev);
>>   	struct mipi_config *mipi_config = dev_priv->vbt.dsi.config;
>> +	enum gpiod_flags flags = panel_is_on ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
> 
> Can't we just tell it not to change the current setting?

We could use GPIOD_ASIS for that, but with the SoC pins (when the PMIC is
not used for backlight control) things get a bit muddy, I've seen several
instances of this message from drivers/pinctrl/intel/pinctrl-baytrail.c
trigger when the GOP did not init the panel:

dev_warn(vg->dev, FW_BUG "pin %u forcibly re-configured as GPIO\n", offset);

And in that case with GPIOD_ASIS I have no idea which we initially get,
so this approach, where we clearly define which initial value we want,
seems better.

Regards,

Hans

p.s.

The intel-gfx CI seems to seriously dislike my patches lately, almost
always failing them; and usually on what at least seem to be unrelated
test-cases. Any advice on how to deal with this?




> 
>>   
>>   	if ((IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv)) &&
>>   	    (mipi_config->pwm_blc == PPS_BLC_PMIC)) {
>> -		intel_dsi->gpio_panel =
>> -			gpiod_get(dev->dev, "panel", GPIOD_OUT_HIGH);
>> -
>> +		intel_dsi->gpio_panel = gpiod_get(dev->dev, "panel", flags);
>>   		if (IS_ERR(intel_dsi->gpio_panel)) {
>>   			DRM_ERROR("Failed to own gpio for panel control\n");
>>   			intel_dsi->gpio_panel = NULL;
>> diff --git a/drivers/gpu/drm/i915/display/vlv_dsi.c b/drivers/gpu/drm/i915/display/vlv_dsi.c
>> index 178d0fffba5b..e86e4a11e199 100644
>> --- a/drivers/gpu/drm/i915/display/vlv_dsi.c
>> +++ b/drivers/gpu/drm/i915/display/vlv_dsi.c
>> @@ -1910,7 +1910,7 @@ void vlv_dsi_init(struct drm_i915_private *dev_priv)
>>   
>>   	vlv_dphy_param_init(intel_dsi);
>>   
>> -	intel_dsi_vbt_gpio_init(intel_dsi);
>> +	intel_dsi_vbt_gpio_init(intel_dsi, current_mode != NULL);
>>   
>>   	drm_connector_init(dev, connector, &intel_dsi_connector_funcs,
>>   			   DRM_MODE_CONNECTOR_DSI);
>> -- 
>> 2.23.0
>