linux-kernel - [PATCH v3] drm/ast: Fix ARM compatibility

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Date:   Fri, 21 Apr 2023 08:33:54 +0800
From:   Jammy Huang <jammy_huang@...eedtech.com>
To:     <airlied@...hat.com>, <tzimmermann@...e.de>
CC:     <airlied@...il.com>, <daniel@...ll.ch>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v3] drm/ast: Fix ARM compatibility

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

Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
---
 v2 changes:
  - Use MMIO after AST2500 which enable MMIO by default.
 v3 changes:
  - Correct comments
---
 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 f83ce77127cb..a6d0ee4da2b8 100644
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -425,11 +425,12 @@ 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;
 	}

base-commit: e62252bc55b6d4eddc6c2bdbf95a448180d6a08d
-- 
2.25.1