Re: [PATCH] drm/i915: Retry few time if gpiod_get fails during intel_dsi_init

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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@xxxxxxxxx>
---
  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;
  		}

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