[Intel-gfx] [PATCH] drm/i915: Retry few time if gpiod_get fails during intel_dsi_init

[Kumar, Shobhit]

On 01/19/2016 08:45 PM, Shobhit Kumar wrote:
> INTEL_SOC_PMIC is loading later than I915 failing the gpiod_get and
> pwm_get calls in i915. Add a retry to give time for the INTEL_SOC_PMIC
> to load. This was fine till now but broke in latest kernel. Maybe load
> time for the INTEL_SOC_PMIC has increased.
>
> Since the lookup tables for GPIO (panel enable) and PWM both are
> exported by same intel_soc_pmic driver, just retrying for the driver to
> load in intel_dsi_init is sufficient. By the time we come to
> setup_backlight, pwm would have been exported as well.

Maybe we should play with initcalls here but I was not sure how it will 
impact if I change it for PMIC driver. IIRC, this discussion came up 
from Daniel at the time of original patches also but somehow did not 
close decidedly and has come back as a regression.

Regards
Shobhit

>
> Signed-off-by: Shobhit Kumar <shobhit.kumar at intel.com>
> ---
>   drivers/gpu/drm/i915/intel_dsi.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
> index 91cef35..e309ef6 100644
> --- a/drivers/gpu/drm/i915/intel_dsi.c
> +++ b/drivers/gpu/drm/i915/intel_dsi.c
> @@ -1192,10 +1192,14 @@ void intel_dsi_init(struct drm_device *dev)
>   	 * Panel control.
>   	 */
>   	if (dev_priv->vbt.dsi.config->pwm_blc == PPS_BLC_PMIC) {
> +		int retry = 4;
> +		do {
>   		intel_dsi->gpio_panel =
>   			gpiod_get(dev->dev, "panel", GPIOD_OUT_HIGH);
> +			msleep(50);
> +		} while (IS_ERR(intel_dsi->gpio_panel) && --retry);
>
> -		if (IS_ERR(intel_dsi->gpio_panel)) {
> +		if (!retry) {
>   			DRM_ERROR("Failed to own gpio for panel control\n");
>   			intel_dsi->gpio_panel = NULL;
>   		}
>