drm/udl: Add register constants for framebuffer scanout addresses

Add register constants for the framebuffer scanout addresses and
update the related helper functions. No functional changes.

v2:
	* extract address bytes with helper macros (Javier)
	* fix comments
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221006095355.23579-16-tzimmermann@suse.de

drivers/gpu/drm/udl/udl_modeset.c

@@ -8,6 +8,8 @@
  * Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>
  */
 
+#include <linux/bitfield.h>
+
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc_helper.h>
@@ -59,23 +61,36 @@ static char *udl_set_color_depth(char *buf, u8 selection)
 	return udl_set_register(buf, UDL_REG_COLORDEPTH, selection);
 }
 
-static char *udl_set_base16bpp(char *wrptr, u32 base)
+static char *udl_set_base16bpp(char *buf, u32 base)
 {
-	/* the base pointer is 16 bits wide, 0x20 is hi byte. */
-	wrptr = udl_set_register(wrptr, 0x20, base >> 16);
-	wrptr = udl_set_register(wrptr, 0x21, base >> 8);
-	return udl_set_register(wrptr, 0x22, base);
+	/* the base pointer is 24 bits wide, 0x20 is hi byte. */
+	u8 reg20 = FIELD_GET(UDL_BASE_ADDR2_MASK, base);
+	u8 reg21 = FIELD_GET(UDL_BASE_ADDR1_MASK, base);
+	u8 reg22 = FIELD_GET(UDL_BASE_ADDR0_MASK, base);
+
+	buf = udl_set_register(buf, UDL_REG_BASE16BPP_ADDR2, reg20);
+	buf = udl_set_register(buf, UDL_REG_BASE16BPP_ADDR1, reg21);
+	buf = udl_set_register(buf, UDL_REG_BASE16BPP_ADDR0, reg22);
+
+	return buf;
 }
 
 /*
  * DisplayLink HW has separate 16bpp and 8bpp framebuffers.
  * In 24bpp modes, the low 323 RGB bits go in the 8bpp framebuffer
  */
-static char *udl_set_base8bpp(char *wrptr, u32 base)
+static char *udl_set_base8bpp(char *buf, u32 base)
 {
-	wrptr = udl_set_register(wrptr, 0x26, base >> 16);
-	wrptr = udl_set_register(wrptr, 0x27, base >> 8);
-	return udl_set_register(wrptr, 0x28, base);
+	/* the base pointer is 24 bits wide, 0x26 is hi byte. */
+	u8 reg26 = FIELD_GET(UDL_BASE_ADDR2_MASK, base);
+	u8 reg27 = FIELD_GET(UDL_BASE_ADDR1_MASK, base);
+	u8 reg28 = FIELD_GET(UDL_BASE_ADDR0_MASK, base);
+
+	buf = udl_set_register(buf, UDL_REG_BASE8BPP_ADDR2, reg26);
+	buf = udl_set_register(buf, UDL_REG_BASE8BPP_ADDR1, reg27);
+	buf = udl_set_register(buf, UDL_REG_BASE8BPP_ADDR0, reg28);
+
+	return buf;
 }
 
 static char *udl_set_register_16(char *wrptr, u8 reg, u16 value)

drivers/gpu/drm/udl/udl_proto.h

@@ -3,6 +3,8 @@
 #ifndef UDL_PROTO_H
 #define UDL_PROTO_H
 
+#include <linux/bits.h>
+
 /* Color depth */
 #define UDL_REG_COLORDEPTH		0x00
 #define UDL_COLORDEPTH_16BPP		0
@@ -31,6 +33,18 @@
 #define UDL_BLANKMODE_HSYNC_OFF		0x05 /* hsync off, blanked */
 #define UDL_BLANKMODE_POWERDOWN		0x07 /* powered off; requires modeset */
 
+/* Framebuffer address */
+#define UDL_REG_BASE16BPP_ADDR2		0x20
+#define UDL_REG_BASE16BPP_ADDR1		0x21
+#define UDL_REG_BASE16BPP_ADDR0		0x22
+#define UDL_REG_BASE8BPP_ADDR2		0x26
+#define UDL_REG_BASE8BPP_ADDR1		0x27
+#define UDL_REG_BASE8BPP_ADDR0		0x28
+
+#define UDL_BASE_ADDR0_MASK		GENMASK(7, 0)
+#define UDL_BASE_ADDR1_MASK		GENMASK(15, 8)
+#define UDL_BASE_ADDR2_MASK		GENMASK(23, 16)
+
 /* Lock/unlock video registers */
 #define UDL_REG_VIDREG			0xff
 #define UDL_VIDREG_LOCK			0x00