drm/vc4: hvs: Configure the HVS COB allocations

The HVS Composite Output Buffer (COB) is the memory used to
generate the output pixel data.
Until now the vc4 driver has been relying on the firmware to
have set these to sensible values.

In testing triple screen support it has been noted that only
1 line was being assigned to HVS channel 2. Whilst that is fine
for the transposer (TXP), and indeed needed as only some pixels
have an alpha channel, it is insufficient to run a live display.

Split the COB more evenly between the 3 HVS channels.

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-v1-1-1f8e0770798b@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/vc4/vc4_hvs.c

@@ -806,7 +806,7 @@ static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
 	struct vc4_hvs *hvs = NULL;
 	int ret;
 	u32 dispctrl;
-	u32 reg;
+	u32 reg, top;
 
 	hvs = __vc4_hvs_alloc(vc4, NULL);
 	if (IS_ERR(hvs))
@@ -915,6 +915,60 @@ static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
 
 	HVS_WRITE(SCALER_DISPCTRL, dispctrl);
 
+	/* Recompute Composite Output Buffer (COB) allocations for the displays
+	 */
+	if (!vc4->is_vc5) {
+		/* The COB is 20736 pixels, or just over 10 lines at 2048 wide.
+		 * The bottom 2048 pixels are full 32bpp RGBA (intended for the
+		 * TXP composing RGBA to memory), whilst the remainder are only
+		 * 24bpp RGB.
+		 *
+		 * Assign 3 lines to channels 1 & 2, and just over 4 lines to
+		 * channel 0.
+		 */
+		#define VC4_COB_SIZE		20736
+		#define VC4_COB_LINE_WIDTH	2048
+		#define VC4_COB_NUM_LINES	3
+		reg = 0;
+		top = VC4_COB_LINE_WIDTH * VC4_COB_NUM_LINES;
+		reg |= (top - 1) << 16;
+		HVS_WRITE(SCALER_DISPBASE2, reg);
+		reg = top;
+		top += VC4_COB_LINE_WIDTH * VC4_COB_NUM_LINES;
+		reg |= (top - 1) << 16;
+		HVS_WRITE(SCALER_DISPBASE1, reg);
+		reg = top;
+		top = VC4_COB_SIZE;
+		reg |= (top - 1) << 16;
+		HVS_WRITE(SCALER_DISPBASE0, reg);
+	} else {
+		/* The COB is 44416 pixels, or 10.8 lines at 4096 wide.
+		 * The bottom 4096 pixels are full RGBA (intended for the TXP
+		 * composing RGBA to memory), whilst the remainder are only
+		 * RGB. Addressing is always pixel wide.
+		 *
+		 * Assign 3 lines of 4096 to channels 1 & 2, and just over 4
+		 * lines. to channel 0.
+		 */
+		#define VC5_COB_SIZE		44416
+		#define VC5_COB_LINE_WIDTH	4096
+		#define VC5_COB_NUM_LINES	3
+		reg = 0;
+		top = VC5_COB_LINE_WIDTH * VC5_COB_NUM_LINES;
+		reg |= top << 16;
+		HVS_WRITE(SCALER_DISPBASE2, reg);
+		top += 16;
+		reg = top;
+		top += VC5_COB_LINE_WIDTH * VC5_COB_NUM_LINES;
+		reg |= top << 16;
+		HVS_WRITE(SCALER_DISPBASE1, reg);
+		top += 16;
+		reg = top;
+		top = VC5_COB_SIZE;
+		reg |= top << 16;
+		HVS_WRITE(SCALER_DISPBASE0, reg);
+	}
+
 	ret = devm_request_irq(dev, platform_get_irq(pdev, 0),
 			       vc4_hvs_irq_handler, 0, "vc4 hvs", drm);
 	if (ret)