[PATCH 5.15 045/159] drm/ast: Fix ARM compatibility

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Jammy Huang <jammy_huang@aspeedtech.com>

[ Upstream commit 4327a6137ed43a091d900b1ac833345d60f32228 ]

ARM architecture only has 'memory', so all devices are accessed by
MMIO if possible.

Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230421003354.27767-1-jammy_huang@aspeedtech.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/ast/ast_main.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
index 79a3618679554..754a08c92d3d1 100644
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -423,11 +423,12 @@ struct ast_private *ast_device_create(const struct drm_driver *drv,
 		return ERR_PTR(-EIO);
 
 	/*
-	 * If we don't have IO space at all, use MMIO now and
-	 * assume the chip has MMIO enabled by default (rev 0x20
-	 * and higher).
+	 * After AST2500, MMIO is enabled by default, and it should be adopted
+	 * to be compatible with Arm.
 	 */
-	if (!(pci_resource_flags(pdev, 2) & IORESOURCE_IO)) {
+	if (pdev->revision >= 0x40) {
+		ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
+	} else if (!(pci_resource_flags(pdev, 2) & IORESOURCE_IO)) {
 		drm_info(dev, "platform has no IO space, trying MMIO\n");
 		ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
 	}
-- 
2.39.2