drm/mgag200: Move TAGFIFO reset into separate function

The TAGFIFO state is now reset in mgag200_g200er_reset_tagfifo().

v2:
	* define MGAREG_SEQ1_SCROFF
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: John Donnelly <John.p.donnelly@oracle.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Emil Velikov <emil.velikov@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200515083233.32036-10-tzimmermann@suse.de

drivers/gpu/drm/mgag200/mgag200_drv.h

@@ -49,6 +49,12 @@
 		WREG8(ATTR_DATA, v);				\
 	} while (0)						\
 
+#define RREG_SEQ(reg, v)					\
+	do {							\
+		WREG8(MGAREG_SEQ_INDEX, reg);			\
+		v = RREG8(MGAREG_SEQ_DATA);			\
+	} while (0)						\
+
 #define WREG_SEQ(reg, v)					\
 	do {							\
 		WREG8(MGAREG_SEQ_INDEX, reg);			\

drivers/gpu/drm/mgag200/mgag200_mode.c

@@ -1106,6 +1106,33 @@ static void mgag200_set_format_regs(struct mga_device *mdev,
 	WREG_ECRT(3, crtcext3);
 }
 
+static void mgag200_g200er_reset_tagfifo(struct mga_device *mdev)
+{
+	static uint32_t RESET_FLAG = 0x00200000; /* undocumented magic value */
+	u8 seq1;
+	u32 memctl;
+
+	/* screen off */
+	RREG_SEQ(0x01, seq1);
+	seq1 |= MGAREG_SEQ1_SCROFF;
+	WREG_SEQ(0x01, seq1);
+
+	memctl = RREG32(MGAREG_MEMCTL);
+
+	memctl |= RESET_FLAG;
+	WREG32(MGAREG_MEMCTL, memctl);
+
+	udelay(1000);
+
+	memctl &= ~RESET_FLAG;
+	WREG32(MGAREG_MEMCTL, memctl);
+
+	/* screen on */
+	RREG_SEQ(0x01, seq1);
+	seq1 &= ~MGAREG_SEQ1_SCROFF;
+	WREG_SEQ(0x01, seq1);
+}
+
 static int mga_crtc_mode_set(struct drm_crtc *crtc,
 				struct drm_display_mode *mode,
 				struct drm_display_mode *adjusted_mode,
@@ -1240,22 +1267,8 @@ static int mga_crtc_mode_set(struct drm_crtc *crtc,
 
 	mgag200_set_mode_regs(mdev, mode);
 
-	/* reset tagfifo */
-	if (mdev->type == G200_ER) {
-		u32 mem_ctl = RREG32(MGAREG_MEMCTL);
-		u8 seq1;
-
-		/* screen off */
-		WREG8(MGAREG_SEQ_INDEX, 0x01);
-		seq1 = RREG8(MGAREG_SEQ_DATA) | 0x20;
-		WREG8(MGAREG_SEQ_DATA, seq1);
-
-		WREG32(MGAREG_MEMCTL, mem_ctl | 0x00200000);
-		udelay(1000);
-		WREG32(MGAREG_MEMCTL, mem_ctl & ~0x00200000);
-
-		WREG8(MGAREG_SEQ_DATA, seq1 & ~0x20);
-	}
+	if (mdev->type == G200_ER)
+		mgag200_g200er_reset_tagfifo(mdev);
 
 
 	if (IS_G200_SE(mdev)) {

drivers/gpu/drm/mgag200/mgag200_reg.h

@@ -235,6 +235,9 @@
 /* MMIO VGA registers */
 #define MGAREG_SEQ_INDEX	0x1fc4
 #define MGAREG_SEQ_DATA		0x1fc5
+
+#define MGAREG_SEQ1_SCROFF	BIT(5)
+
 #define MGAREG_CRTC_INDEX	0x1fd4
 #define MGAREG_CRTC_DATA	0x1fd5
 #define MGAREG_CRTCEXT_INDEX	0x1fde