drm/radeon/kms: add hw_i2c module option

Turn off hw i2c by default except for mm i2c which
is hw only until we sort out the remaining prescale
issues on older chips.  hw i2c can be enabled with
hw_i2c=1.
Signed-off-by: NAlex Deucher <alexdeucher@gmail.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon.h

@@ -92,6 +92,7 @@ extern int radeon_new_pll;
 extern int radeon_dynpm;
 extern int radeon_audio;
 extern int radeon_disp_priority;
+extern int radeon_hw_i2c;
 
 /*
  * Copy from radeon_drv.h so we don't have to include both and have conflicting

drivers/gpu/drm/radeon/radeon_drv.c

@@ -93,6 +93,7 @@ int radeon_new_pll = -1;
 int radeon_dynpm = -1;
 int radeon_audio = 1;
 int radeon_disp_priority = 0;
+int radeon_hw_i2c = 0;
 
 MODULE_PARM_DESC(no_wb, "Disable AGP writeback for scratch registers");
 module_param_named(no_wb, radeon_no_wb, int, 0444);
@@ -139,6 +140,9 @@ module_param_named(audio, radeon_audio, int, 0444);
 MODULE_PARM_DESC(disp_priority, "Display Priority (0 = auto, 1 = normal, 2 = high)");
 module_param_named(disp_priority, radeon_disp_priority, int, 0444);
 
+MODULE_PARM_DESC(hw_i2c, "hw i2c engine enable (0 = disable)");
+module_param_named(hw_i2c, radeon_hw_i2c, int, 0444);
+
 static int radeon_suspend(struct drm_device *dev, pm_message_t state)
 {
 	drm_radeon_private_t *dev_priv = dev->dev_private;

drivers/gpu/drm/radeon/radeon_i2c.c

@@ -879,9 +879,11 @@ struct radeon_i2c_chan *radeon_i2c_create(struct drm_device *dev,
 	i2c->adapter.owner = THIS_MODULE;
 	i2c->dev = dev;
 	i2c_set_adapdata(&i2c->adapter, i2c);
-	if (rec->hw_capable &&
+	if (rec->mm_i2c ||
+	    (rec->hw_capable &&
+	     radeon_hw_i2c &&
 	     ((rdev->family <= CHIP_RS480) ||
-	     ((rdev->family >= CHIP_RV515) && (rdev->family <= CHIP_R580)))) {
+	      ((rdev->family >= CHIP_RV515) && (rdev->family <= CHIP_R580))))) {
 		/* set the radeon hw i2c adapter */
 		sprintf(i2c->adapter.name, "Radeon i2c hw bus %s", name);
 		i2c->adapter.algo = &radeon_i2c_algo;