linux-kernel - Re: [PATCH] gma500: Skip bogus LVDS VBT mode and check for LVDS before adding backlight

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Date:	Wed, 11 May 2011 21:58:08 +0200
From:	Patrik Jakobsson <patrik.r.jakobsson@...il.com>
To:	Alan Cox <alan@...ux.intel.com>
Cc:	greg@...ah.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gma500: Skip bogus LVDS VBT mode and check for LVDS
 before adding backlight

On Wed, May 11, 2011 at 06:55:53PM +0100, Alan Cox wrote:
> On Wed, 11 May 2011 19:20:53 +0200
> Patrik Jakobsson <patrik.r.jakobsson@...il.com> wrote:
> 
> > On the Fit-PC2 the VBT reports an invalid fixed panel mode for LVDS,
> > this gets in the way for SDVO. This patch makes VBT parsing skip the
> > invalid mode. When there is no LVDS output the backlight support
> > crashes so the patch also checks for this before enabling it.
> 
> Looks good for now. The backlight is a bit more complicated I think
> (users can turn on the LVDS at runtime in theory) but we can handle
> that later so long as we tag it with a /* FIXME: Handle turning on LVDS
> at runtime */
> 
> Alan

Backlight is only disabled in case no LVDS modes can be found. And in that
case, no LVDS connector gets added. Am I understanding you correctly if
"in theory" means LVDS can be hotplugged? In that case we have to call
psb_intel_lvds_init when hotplug occurs so the output gets added. If so, we
should put psb_backlight_init() there.

Please try the following patch on a system with LVDS hooked-up to something.

-Patrik

---

diff --git a/drivers/staging/gma500/psb_drv.c b/drivers/staging/gma500/psb_drv.c
index 46ab028..ed7be24 100644
--- a/drivers/staging/gma500/psb_drv.c
+++ b/drivers/staging/gma500/psb_drv.c
@@ -663,9 +663,6 @@ static int psb_driver_load(struct drm_device *dev, unsigned long chipset)
 		drm_kms_helper_poll_init(dev);
 	}
 
-	ret = psb_backlight_init(dev);
-	if (ret)
-		return ret;
 #if 0
 	/*enable runtime pm at last*/
 	pm_runtime_enable(&dev->pdev->dev);
diff --git a/drivers/staging/gma500/psb_intel_bios.c b/drivers/staging/gma500/psb_intel_bios.c
index 48ac8ba..417965d 100644
--- a/drivers/staging/gma500/psb_intel_bios.c
+++ b/drivers/staging/gma500/psb_intel_bios.c
@@ -154,10 +154,15 @@ static void parse_lfp_panel_data(struct drm_psb_private *dev_priv,
 
 	fill_detail_timing_data(panel_fixed_mode, dvo_timing);
 
-	dev_priv->lfp_lvds_vbt_mode = panel_fixed_mode;
-
-	DRM_DEBUG("Found panel mode in BIOS VBT tables:\n");
-	drm_mode_debug_printmodeline(panel_fixed_mode);
+	if (panel_fixed_mode->htotal > 0 && panel_fixed_mode->vtotal > 0) {
+		dev_priv->lfp_lvds_vbt_mode = panel_fixed_mode;
+		DRM_DEBUG("Found panel mode in BIOS VBT tables:\n");
+		drm_mode_debug_printmodeline(panel_fixed_mode);
+	} else {
+		DRM_DEBUG("Ignoring bogus LVDS VBT mode.\n");
+		dev_priv->lvds_vbt = 0;
+		kfree(panel_fixed_mode);
+	}
 
 	return;
 }
diff --git a/drivers/staging/gma500/psb_intel_lvds.c b/drivers/staging/gma500/psb_intel_lvds.c
index b0a225b..081402a 100644
--- a/drivers/staging/gma500/psb_intel_lvds.c
+++ b/drivers/staging/gma500/psb_intel_lvds.c
@@ -843,6 +843,9 @@ void psb_intel_lvds_init(struct drm_device *dev,
 		goto failed_find;
 	}
 
+	if (psb_backlight_init(dev))
+		DRM_DEBUG("Backlight initialization failed\n");
+
 	/*
 	 * Blacklist machines with BIOSes that list an LVDS panel without
 	 * actually having one.
--
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