Re: [PATCH 15/15] drm/ast: Fix open-coded scu_rev access

[Jocelyn Falempe]

On 23/03/2026 16:56, Thomas Zimmermann wrote:

Replace all open-coded access to P2A and SCU registers in the device
detection with the appropriate calls to ast_moutdwm() and ast_mindwm().
Use P2A and MCR register constants. Name variables according to registers.

Thanks, it looks good to me.

Reviewed-by: Jocelyn Falempe <jfale...@redhat.com>

Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>
---
  drivers/gpu/drm/ast/ast_drv.c | 13 ++++++-------
  drivers/gpu/drm/ast/ast_reg.h |  1 +
  2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/ast/ast_drv.c b/drivers/gpu/drm/ast/ast_drv.c
index 6fe549f16309..ba6cf5fa901c 100644
--- a/drivers/gpu/drm/ast/ast_drv.c
+++ b/drivers/gpu/drm/ast/ast_drv.c
@@ -242,7 +242,7 @@ static int ast_detect_chip(struct pci_dev *pdev,
        enum ast_config_mode config_mode = ast_use_defaults;
        uint32_t scu_rev = 0xffffffff;
        enum ast_chip chip;
-       u32 data;
+       u32 data, p2a04, scu07c;
        u8 vgacrd0, vgacrd1;

/*

@@ -275,14 +275,13 @@ static int ast_detect_chip(struct pci_dev *pdev,
                        }

/* Double check that it's actually working */

-                       data = __ast_read32(regs, 0xf004);
-                       if ((data != 0xffffffff) && (data != 0x00)) {
+                       p2a04 = __ast_read32(regs, AST_REG_P2A04);
+                       if (p2a04 != 0xffffffff && p2a04 != 0x00000000) {
                                config_mode = ast_use_p2a;

- /* Read SCU7c (silicon revision register) */

-                               __ast_write32(regs, 0xf004, AST_REG_MCR00);
-                               __ast_write32(regs, 0xf000, 0x1);
-                               scu_rev = __ast_read32(regs, 0x1207c);
+                               /* Read SCU7C (silicon revision register) */
+                               scu07c = __ast_mindwm(regs, AST_REG_SCU07C);
+                               scu_rev = scu07c & 
AST_REG_SCU07C_CHIP_BONDING_MASK;
                        }
                }
        }
diff --git a/drivers/gpu/drm/ast/ast_reg.h b/drivers/gpu/drm/ast/ast_reg.h
index 9d6ea0765990..00e496d61551 100644
--- a/drivers/gpu/drm/ast/ast_reg.h
+++ b/drivers/gpu/drm/ast/ast_reg.h
@@ -190,6 +190,7 @@
  #define AST_REG_SCU040                                AST_REG_SCU(0x040)
  #define AST_REG_SCU070                                AST_REG_SCU(0x070)
  #define AST_REG_SCU07C                                AST_REG_SCU(0x07c)
+#define AST_REG_SCU07C_CHIP_BONDING_MASK       GENMASK(15, 8)
  #define AST_REG_SCU084                                AST_REG_SCU(0x084)
  #define AST_REG_SCU088                                AST_REG_SCU(0x088)
  #define AST_REG_SCU08C                                AST_REG_SCU(0x08c)