[RFC PATCH 5/7] drm/edid: Switch DDC when reading the EDID

Seth Forshee seth.forshee at canonical.com
Mon Aug 20 08:31:02 PDT 2012


Some dual graphics machines support muxing the DDC separately from the
display, so make use of this functionality when reading the EDID on the
inactive GPU. Also serialize drm_get_edid() with a mutex to avoid races
on the DDC mux state.

Signed-off-by: Seth Forshee <seth.forshee at canonical.com>
---
 drivers/gpu/drm/drm_edid.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index a8743c3..1a4b661 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -31,6 +31,7 @@
 #include <linux/slab.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
+#include <linux/vga_switcheroo.h>
 #include "drmP.h"
 #include "drm_edid.h"
 #include "drm_edid_modes.h"
@@ -82,6 +83,8 @@ struct detailed_mode_closure {
 #define LEVEL_GTF2	2
 #define LEVEL_CVT	3
 
+static DEFINE_MUTEX(drm_edid_mutex);
+
 static struct edid_quirk {
 	char vendor[4];
 	int product_id;
@@ -395,12 +398,26 @@ struct edid *drm_get_edid(struct drm_connector *connector,
 			  struct i2c_adapter *adapter)
 {
 	struct edid *edid = NULL;
+	struct pci_dev *pdev = connector->dev->pdev;
+	struct pci_dev *active_pdev = NULL;
+
+	mutex_lock(&drm_edid_mutex);
+
+	if (pdev) {
+		active_pdev = vga_switcheroo_get_active_client();
+		if (active_pdev != pdev)
+			vga_switcheroo_switch_ddc(pdev);
+	}
 
 	if (drm_probe_ddc(adapter))
 		edid = (struct edid *)drm_do_get_edid(connector, adapter);
 
+	if (active_pdev && active_pdev != pdev)
+		vga_switcheroo_switch_ddc(active_pdev);
+
 	connector->display_info.raw_edid = (char *)edid;
 
+	mutex_unlock(&drm_edid_mutex);
 	return edid;
 
 }
-- 
1.7.9.5



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