Re: [PATCH v2] drm/i915/bxt: use NULL for GPIO connection ID

From: Mika Kahola <mika.kahola@intel.com>
To: "Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"David Airlie" <airlied@linux.ie>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Subject: Re: [PATCH v2] drm/i915/bxt: use NULL for GPIO connection ID
Date: Thu, 17 Aug 2017 14:06:54 +0300	[thread overview]
Message-ID: <1502968014.12240.7.camel@intel.com> (raw)
In-Reply-To: <20170817105541.63914-1-andriy.shevchenko@linux.intel.com>

Tested with GLK + MIPI/DSI panel (AU Optronics B101UAN01)

Tested-by: Mika Kahola <mika.kahola@intel.com>

On Thu, 2017-08-17 at 13:55 +0300, Andy Shevchenko wrote:
> The commit 213e08ad60ba
> 	("drm/i915/bxt: add bxt dsi gpio element support")
> enables GPIO support for Broxton based platforms.
> 
> While using that API we might get into troubles in the future,
> because
> we can't rely on label name in the driver since vendor firmware might
> provide any GPIO pin there, e.g. "reset", and even mark it in _DSD
> (in
> which case the request will fail).
> 
> To avoid inconsistency and potential issues we have two options:
> a) generate GPIO ACPI mapping table and supply it via
>    acpi_dev_add_driver_gpios(), or
> b) just pass NULL as connection ID.
> 
> The b) approach is much simpler and would work since the driver
> relies
> on GPIO indices only. Moreover, the _CRS fallback mechanism, when
> requesting GPIO, has been made stricter, and supplying non-NULL
> connection ID when neither _DSD, nor GPIO ACPI mapping is present, is
> making request fail.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101921
> Fixes: f10e4bf6632b ("gpio: acpi: Even more tighten up ACPI GPIO
> lookups")
> Cc: Mika Kahola <mika.kahola@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> v2:
>  - adjust commit message for proper time tenses
>  - add Fixes: and Bugzilla: tags
>  drivers/gpu/drm/i915/intel_dsi_vbt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dsi_vbt.c
> b/drivers/gpu/drm/i915/intel_dsi_vbt.c
> index 7158c7ce9c09..91c07b0c8db9 100644
> --- a/drivers/gpu/drm/i915/intel_dsi_vbt.c
> +++ b/drivers/gpu/drm/i915/intel_dsi_vbt.c
> @@ -306,7 +306,7 @@ static void bxt_exec_gpio(struct drm_i915_private
> *dev_priv,
>  
>  	if (!gpio_desc) {
>  		gpio_desc = devm_gpiod_get_index(dev_priv->drm.dev,
> -						 "panel",
> gpio_index,
> +						 NULL, gpio_index,
>  						 value ?
> GPIOD_OUT_LOW :
>  						 GPIOD_OUT_HIGH);
>  
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