drm/ast: Fix video broken in some resolutions on ast2600

Some cases are not handled well for ast2600.
Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220916091706.4559-1-jammy_huang@aspeedtech.com

drivers/gpu/drm/ast/ast_mode.c

@@ -313,7 +313,7 @@ static void ast_set_crtc_reg(struct ast_private *ast,
 	u8 jreg05 = 0, jreg07 = 0, jreg09 = 0, jregAC = 0, jregAD = 0, jregAE = 0;
 	u16 temp, precache = 0;
 
-	if ((ast->chip == AST2500) &&
+	if ((ast->chip == AST2500 || ast->chip == AST2600) &&
 	    (vbios_mode->enh_table->flags & AST2500PreCatchCRT))
 		precache = 40;
 
@@ -354,6 +354,12 @@ static void ast_set_crtc_reg(struct ast_private *ast,
 	ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xAC, 0x00, jregAC);
 	ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xAD, 0x00, jregAD);
 
+	// Workaround for HSync Time non octave pixels (1920x1080@60Hz HSync 44 pixels);
+	if ((ast->chip == AST2600) && (mode->crtc_vdisplay == 1080))
+		ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xFC, 0xFD, 0x02);
+	else
+		ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xFC, 0xFD, 0x00);
+
 	/* vert timings */
 	temp = (mode->crtc_vtotal) - 2;
 	if (temp & 0x100)
@@ -431,7 +437,7 @@ static void ast_set_dclk_reg(struct ast_private *ast,
 {
 	const struct ast_vbios_dclk_info *clk_info;
 
-	if (ast->chip == AST2500)
+	if ((ast->chip == AST2500) || (ast->chip == AST2600))
 		clk_info = &dclk_table_ast2500[vbios_mode->enh_table->dclk_index];
 	else
 		clk_info = &dclk_table[vbios_mode->enh_table->dclk_index];