drm/mgag200: Move register initialization into helper function

The mgag200 driver maps registers into the address space. Move the
code into a separate helper function. No functional changes.

One small difference is in the handling of SDRAM/SGRAM. MGA devices
can come with either SDRAM or SGRAM. So far, the driver checked for
SDRAM, which is the common case. The patch moves this code into a
separate helper and checks for SGRAM, which is the special case. The
test itself is the same as before.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200730102844.10995-3-tzimmermann@suse.de

drivers/gpu/drm/mgag200/mgag200_drv.c

@@ -44,18 +44,26 @@ static struct drm_driver mgag200_driver = {
  * DRM device
  */
 
-static int mgag200_device_init(struct mga_device *mdev, unsigned long flags)
+static bool mgag200_has_sgram(struct mga_device *mdev)
 {
 	struct drm_device *dev = &mdev->base;
-	int ret, option;
+	u32 option;
+	int ret;
 
-	mdev->flags = mgag200_flags_from_driver_data(flags);
-	mdev->type = mgag200_type_from_driver_data(flags);
+	ret = pci_read_config_dword(dev->pdev, PCI_MGA_OPTION, &option);
+	if (drm_WARN(dev, ret, "failed to read PCI config dword: %d\n", ret))
+		return false;
+
+	return !!(option & PCI_MGA_OPTION_HARDPWMSK);
+}
 
-	pci_read_config_dword(dev->pdev, PCI_MGA_OPTION, &option);
-	mdev->has_sdram = !(option & (1 << 14));
+static int mgag200_regs_init(struct mga_device *mdev)
+{
+	struct drm_device *dev = &mdev->base;
+
+	mdev->has_sdram = !mgag200_has_sgram(mdev);
 
-	/* BAR 0 is the framebuffer, BAR 1 contains registers */
+	/* BAR 1 contains registers */
 	mdev->rmmio_base = pci_resource_start(dev->pdev, 1);
 	mdev->rmmio_size = pci_resource_len(dev->pdev, 1);
 
@@ -69,6 +77,21 @@ static int mgag200_device_init(struct mga_device *mdev, unsigned long flags)
 	if (mdev->rmmio == NULL)
 		return -ENOMEM;
 
+	return 0;
+}
+
+static int mgag200_device_init(struct mga_device *mdev, unsigned long flags)
+{
+	struct drm_device *dev = &mdev->base;
+	int ret;
+
+	mdev->flags = mgag200_flags_from_driver_data(flags);
+	mdev->type = mgag200_type_from_driver_data(flags);
+
+	ret = mgag200_regs_init(mdev);
+	if (ret)
+		return ret;
+
 	/* stash G200 SE model number for later use */
 	if (IS_G200_SE(mdev)) {
 		mdev->unique_rev_id = RREG32(0x1e24);

drivers/gpu/drm/mgag200/mgag200_reg.h

@@ -282,6 +282,8 @@
 #define PCI_MGA_OPTION2		0x50
 #define PCI_MGA_OPTION3		0x54
 
+#define PCI_MGA_OPTION_HARDPWMSK	BIT(14)
+
 #define RAMDAC_OFFSET		0x3c00
 
 /* TVP3026 direct registers */