drm/vc4: hvs: SCALER_DISPBKGND_AUTOHS is only valid on HVS4

The bit used for SCALER_DISPBKGND_AUTOHS in SCALER_DISPBKGNDX
has been repurposed on HVS5 to configure whether a display can
win back-to-back arbitration wins for the COB.

This is not desirable, therefore only select this bit on HVS4,
and explicitly clear it on HVS5.

Fixes: c54619b0 ("drm/vc4: Add support for the BCM2711 HVS5")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20221207-rpi-hvs-crtc-misc-v1-3-1f8e0770798b@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/vc4/vc4_hvs.c

@@ -370,28 +370,30 @@ static int vc4_hvs_init_channel(struct vc4_hvs *hvs, struct drm_crtc *crtc,
 	 * mode.
 	 */
 	dispctrl = SCALER_DISPCTRLX_ENABLE;
+	dispbkgndx = HVS_READ(SCALER_DISPBKGNDX(chan));
 
-	if (!vc4->is_vc5)
+	if (!vc4->is_vc5) {
 		dispctrl |= VC4_SET_FIELD(mode->hdisplay,
 					  SCALER_DISPCTRLX_WIDTH) |
 			    VC4_SET_FIELD(mode->vdisplay,
 					  SCALER_DISPCTRLX_HEIGHT) |
 			    (oneshot ? SCALER_DISPCTRLX_ONESHOT : 0);
-	else
+		dispbkgndx |= SCALER_DISPBKGND_AUTOHS;
+	} else {
 		dispctrl |= VC4_SET_FIELD(mode->hdisplay,
 					  SCALER5_DISPCTRLX_WIDTH) |
 			    VC4_SET_FIELD(mode->vdisplay,
 					  SCALER5_DISPCTRLX_HEIGHT) |
 			    (oneshot ? SCALER5_DISPCTRLX_ONESHOT : 0);
+		dispbkgndx &= ~SCALER5_DISPBKGND_BCK2BCK;
+	}
 
 	HVS_WRITE(SCALER_DISPCTRLX(chan), dispctrl);
 
-	dispbkgndx = HVS_READ(SCALER_DISPBKGNDX(chan));
 	dispbkgndx &= ~SCALER_DISPBKGND_GAMMA;
 	dispbkgndx &= ~SCALER_DISPBKGND_INTERLACE;
 
 	HVS_WRITE(SCALER_DISPBKGNDX(chan), dispbkgndx |
-		  SCALER_DISPBKGND_AUTOHS |
 		  ((!vc4->is_vc5) ? SCALER_DISPBKGND_GAMMA : 0) |
 		  (interlace ? SCALER_DISPBKGND_INTERLACE : 0));
 

drivers/gpu/drm/vc4/vc4_regs.h

@@ -366,6 +366,7 @@
 
 #define SCALER_DISPBKGND0                       0x00000044
 # define SCALER_DISPBKGND_AUTOHS		BIT(31)
+# define SCALER5_DISPBKGND_BCK2BCK		BIT(31)
 # define SCALER_DISPBKGND_INTERLACE		BIT(30)
 # define SCALER_DISPBKGND_GAMMA			BIT(29)
 # define SCALER_DISPBKGND_TESTMODE_MASK		VC4_MASK(28, 25)