[PATCH] drm/mgag200: Add command line option to specify preferred depth

[Rob Clark]

From: Egbert Eich <eich at suse.de>

This adds a command line parameter to override the preferred bpp
on mga g200 server chips, so you can run some servers with low
VRAM at a higher resolution but at 16bpp.

Signed-off-by: Rob Clark <robdclark at gmail.com>
---
An old patch from Egbert that never seemed to land upstream.  I've
rebased it since it seems useful.

 drivers/gpu/drm/mgag200/mgag200_drv.c  | 11 +++++++++++
 drivers/gpu/drm/mgag200/mgag200_main.c | 14 ++++++++++----
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c b/drivers/gpu/drm/mgag200/mgag200_drv.c
index 9ac0078..97166a8 100644
--- a/drivers/gpu/drm/mgag200/mgag200_drv.c
+++ b/drivers/gpu/drm/mgag200/mgag200_drv.c
@@ -22,9 +22,12 @@
  * functions
  */
 int mgag200_modeset = -1;
+int mgag200_preferred_depth __read_mostly = 0;
 
 MODULE_PARM_DESC(modeset, "Disable/Enable modesetting");
 module_param_named(modeset, mgag200_modeset, int, 0400);
+MODULE_PARM_DESC(preferreddepth, "Set preferred bpp");
+module_param_named(preferreddepth, mgag200_preferred_depth, int, 0400);
 
 static struct drm_driver driver;
 
@@ -120,6 +123,14 @@ static int __init mgag200_init(void)
 
 	if (mgag200_modeset == 0)
 		return -EINVAL;
+	switch (mgag200_preferred_depth) {
+	case 0: /* driver default */
+	case 16:
+	case 24:
+		break;
+	default:
+		return -EINVAL;
+	}
 	return drm_pci_init(&driver, &mgag200_pci_driver);
 }
 
diff --git a/drivers/gpu/drm/mgag200/mgag200_main.c b/drivers/gpu/drm/mgag200/mgag200_main.c
index dce8a3e..6411268 100644
--- a/drivers/gpu/drm/mgag200/mgag200_main.c
+++ b/drivers/gpu/drm/mgag200/mgag200_main.c
@@ -14,6 +14,8 @@
 #include <drm/drm_crtc_helper.h>
 #include "mgag200_drv.h"
 
+extern int mgag200_preferred_depth __read_mostly;
+
 static void mga_user_framebuffer_destroy(struct drm_framebuffer *fb)
 {
 	struct mga_framebuffer *mga_fb = to_mga_framebuffer(fb);
@@ -226,10 +228,14 @@ int mgag200_driver_load(struct drm_device *dev, unsigned long flags)
 
 	drm_mode_config_init(dev);
 	dev->mode_config.funcs = (void *)&mga_mode_funcs;
-	if (IS_G200_SE(mdev) && mdev->mc.vram_size < (2048*1024))
-		dev->mode_config.preferred_depth = 16;
-	else
-		dev->mode_config.preferred_depth = 24;
+	if (mgag200_preferred_depth == 0) {
+		if (IS_G200_SE(mdev) && mdev->mc.vram_size < (2048*1024))
+			dev->mode_config.preferred_depth = 16;
+		else
+			dev->mode_config.preferred_depth = 24;
+	} else {
+		dev->mode_config.preferred_depth = mgag200_preferred_depth;
+	}
 	dev->mode_config.prefer_shadow = 1;
 
 	r = mgag200_modeset_init(mdev);
-- 
2.9.3