drm/ast: Handle known struct ast_dramstruct with helpers

Most of struct ast_dramstruct stores hardware state. Some index
values have known or special meaning. The known values are

- 0xffff - Terminal entry in the array
- 0xff00 - Delays the programming for usecs
- 0x0004 - Sets the type of DRAM

Add constants and helper macros for these cases. Also add a helper
macro for testing. Update Gen1 and Gen2+ accordingly.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250706162816.211552-8-tzimmermann@suse.de

1 files changed, 22 insertions, 0 deletions

diff --git a/drivers/gpu/drm/ast/ast_post.h b/drivers/gpu/drm/ast/ast_post.h
index 3a55c32a7eb7..44136856952f 100644
--- a/drivers/gpu/drm/ast/ast_post.h
+++ b/drivers/gpu/drm/ast/ast_post.h
@@ -3,6 +3,7 @@
 #ifndef AST_POST_H
 #define AST_POST_H
 
+#include <linux/limits.h>
 #include <linux/types.h>
 
 struct ast_device;
@@ -13,6 +14,27 @@ struct ast_dramstruct {
 	u32 data;
 };
 
+/* hardware fields */
+#define __AST_DRAMSTRUCT_DRAM_TYPE      0x0004
+
+/* control commands */
+#define __AST_DRAMSTRUCT_UDELAY         0xff00
+#define __AST_DRAMSTRUCT_INVALID        0xffff
+
+#define __AST_DRAMSTRUCT_INDEX(_name) \
+	(__AST_DRAMSTRUCT_ ## _name)
+
+#define AST_DRAMSTRUCT_INIT(_name, _value) \
+	{ __AST_DRAMSTRUCT_INDEX(_name), (_value) }
+
+#define AST_DRAMSTRUCT_UDELAY(_usecs) \
+	AST_DRAMSTRUCT_INIT(UDELAY, _usecs)
+#define AST_DRAMSTRUCT_INVALID \
+	AST_DRAMSTRUCT_INIT(INVALID, U32_MAX)
+
+#define AST_DRAMSTRUCT_IS(_entry, _name) \
+	((_entry)->index == __AST_DRAMSTRUCT_INDEX(_name))
+
 u32 __ast_mindwm(void __iomem *regs, u32 r);
 void __ast_moutdwm(void __iomem *regs, u32 r, u32 v);