[PATCH 4/4] drm/mgag200: Add module parameter to pin all buffers at offset 0

[Thomas Zimmermann]

For hardware that does not interpret the startadd field correctly,
add the module parameter 'hw_bug_no_startadd', which enables the
workaround.

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
---
 drivers/gpu/drm/mgag200/mgag200_drv.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c b/drivers/gpu/drm/mgag200/mgag200_drv.c
index d43951caeea0..79836b09a54a 100644
--- a/drivers/gpu/drm/mgag200/mgag200_drv.c
+++ b/drivers/gpu/drm/mgag200/mgag200_drv.c
@@ -27,6 +27,10 @@ int mgag200_modeset = -1;
 MODULE_PARM_DESC(modeset, "Disable/Enable modesetting");
 module_param_named(modeset, mgag200_modeset, int, 0400);
 
+int mgag200_hw_bug_no_startadd = -1;
+MODULE_PARM_DESC(modeset, "HW does not interpret scanout-buffer start address correctly");
+module_param_named(hw_bug_no_startadd, mgag200_hw_bug_no_startadd, int, 0400);
+
 static struct drm_driver driver;
 
 static const struct pci_device_id pciidlist[] = {
@@ -64,6 +68,10 @@ DEFINE_DRM_GEM_FOPS(mgag200_driver_fops);
 
 static bool mgag200_pin_bo_at_0(const struct mga_device *mdev)
 {
+	if (!mgag200_hw_bug_no_startadd)
+		return false;
+	else if (mgag200_hw_bug_no_startadd > 0)
+		return true;
 	return mdev->flags & MGAG200_FLAG_HW_BUG_NO_STARTADD;
 }
 
-- 
2.23.0