[PATCH 1/1] drm/ast: Remove existing framebuffers before loading driver

[Kai-Heng Feng]

From: Thomas Zimmermann <tzimmermann at suse.de>

BugLink: https://bugs.launchpad.net/bugs/1808183

If vesafb attaches to the AST device, it configures the framebuffer memory
for uncached access by default. When ast.ko later tries to attach itself to
the device, it wants to use write-combining on the framebuffer memory, but
vesefb's existing configuration for uncached access takes precedence. This
results in reduced performance.

Removing the framebuffer's configuration before loding the AST driver fixes
the problem. Other DRM drivers already contain equivalent code.

Link: https://bugzilla.opensuse.org/show_bug.cgi?id=1112963
Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Cc: <stable at vger.kernel.org>
Tested-by: Y.C. Chen <yc_chen at aspeedtech.com>
Reviewed-by: Jean Delvare <jdelvare at suse.de>
Tested-by: Jean Delvare <jdelvare at suse.de>
Signed-off-by: Dave Airlie <airlied at redhat.com>
(cherry picked from commit 5478ad10e7850ce3d8b7056db05ddfa3c9ddad9a)
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 drivers/gpu/drm/ast/ast_drv.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/ast/ast_drv.c b/drivers/gpu/drm/ast/ast_drv.c
index 69dab82a3771..bf589c53b908 100644
--- a/drivers/gpu/drm/ast/ast_drv.c
+++ b/drivers/gpu/drm/ast/ast_drv.c
@@ -60,8 +60,29 @@ static const struct pci_device_id pciidlist[] = {
 
 MODULE_DEVICE_TABLE(pci, pciidlist);
 
+static void ast_kick_out_firmware_fb(struct pci_dev *pdev)
+{
+	struct apertures_struct *ap;
+	bool primary = false;
+
+	ap = alloc_apertures(1);
+	if (!ap)
+		return;
+
+	ap->ranges[0].base = pci_resource_start(pdev, 0);
+	ap->ranges[0].size = pci_resource_len(pdev, 0);
+
+#ifdef CONFIG_X86
+	primary = pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW;
+#endif
+	drm_fb_helper_remove_conflicting_framebuffers(ap, "astdrmfb", primary);
+	kfree(ap);
+}
+
 static int ast_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
+	ast_kick_out_firmware_fb(pdev);
+
 	return drm_get_pci_dev(pdev, ent, &driver);
 }
 
-- 
2.17.1