drm/i915: use GMBUS to manage i2c links

Use the GMBUS interface rather than direct bit banging to grab the EDID
over DDC (and for other forms of auxiliary communication with external
display controllers). The hope is that this method will be much faster
and more reliable than bit banging for fetching EDIDs from buggy monitors
or through switches, though we still preserve the bit banging as a
fallback in case GMBUS fails.

Based on an original patch by Jesse Barnes.

Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 13 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b0692c40b0c..cf08128798a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -34,6 +34,7 @@
 #include "intel_bios.h"
 #include "intel_ringbuffer.h"
 #include <linux/io-mapping.h>
+#include <linux/i2c.h>
 #include <drm/intel-gtt.h>
 
 /* General customization:
@@ -246,6 +247,12 @@ typedef struct drm_i915_private {
 
         void __iomem *regs;
 
+        struct intel_gmbus {
+                struct i2c_adapter adapter;
+                struct i2c_adapter *force_bitbanging;
+                int pin;
+        } *gmbus;
+
         struct pci_dev *bridge_dev;
         struct intel_ring_buffer render_ring;
         struct intel_ring_buffer bsd_ring;
@@ -339,7 +346,7 @@ typedef struct drm_i915_private {
 
         struct notifier_block lid_notifier;
 
-        int crt_ddc_bus; /* 0 = unknown, else GPIO to use for CRT DDC */
+        int crt_ddc_pin;
         struct drm_i915_fence_reg fence_regs[16]; /* assume 965 */
         int fence_reg_start; /* 4 if userland hasn't ioctl'd us yet */
         int num_fence_regs; /* 8 on pre-965, 16 otherwise */
@@ -1070,6 +1077,11 @@ extern int i915_restore_state(struct drm_device *dev);
 extern int i915_save_state(struct drm_device *dev);
 extern int i915_restore_state(struct drm_device *dev);
 
+/* intel_i2c.c */
+extern int intel_setup_gmbus(struct drm_device *dev);
+extern void intel_teardown_gmbus(struct drm_device *dev);
+extern void intel_i2c_reset(struct drm_device *dev);
+
 /* intel_opregion.c */
 extern int intel_opregion_setup(struct drm_device *dev);
 #ifdef CONFIG_ACPI