drm/tidss: implement WA for AM65xx erratum i2000

This patch implements WA for AM65xx erratum i2000, which causes YUV
formats to show wrong colors.

An earlier patch removed a partial WA:

a8d9d7da ("drm/tidss: remove AM65x PG1 YUV erratum code")

The patch explains the reasoning for removal. The change in plans has
been that it has become clear that there are and will be users for PG1
SoCs and as such it's good to implement the WA for PG1s.

This patch adds the WA back so that it is only used on SR1.0 (which is
the new name for PG1). The previous WA code didn't check the SoC
revision, which this patch does.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200812112625.59897-1-tomi.valkeinen@ti.comReviewed-by: Jyri Sarha <jsarha@ti.com>

drivers/gpu/drm/tidss/tidss_dispc.c

@@ -19,6 +19,7 @@
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
+#include <linux/sys_soc.h>
 
 #include <drm/drm_fourcc.h>
 #include <drm/drm_fb_cma_helper.h>
@@ -302,6 +303,8 @@ struct dispc_device {
 	u32 num_fourccs;
 
 	u32 memory_bandwidth_limit;
+
+	struct dispc_errata errata;
 };
 
 static void dispc_write(struct dispc_device *dispc, u16 reg, u32 val)
@@ -2641,6 +2644,19 @@ static int dispc_init_am65x_oldi_io_ctrl(struct device *dev,
 	return 0;
 }
 
+static void dispc_init_errata(struct dispc_device *dispc)
+{
+	static const struct soc_device_attribute am65x_sr10_soc_devices[] = {
+		{ .family = "AM65X", .revision = "SR1.0" },
+		{ /* sentinel */ }
+	};
+
+	if (soc_device_match(am65x_sr10_soc_devices)) {
+		dispc->errata.i2000 = true;
+		dev_info(dispc->dev, "WA for erratum i2000: YUV formats disabled\n");
+	}
+}
+
 int dispc_init(struct tidss_device *tidss)
 {
 	struct device *dev = tidss->dev;
@@ -2664,19 +2680,27 @@ int dispc_init(struct tidss_device *tidss)
 	if (!dispc)
 		return -ENOMEM;
 
+	dispc->tidss = tidss;
+	dispc->dev = dev;
+	dispc->feat = feat;
+
+	dispc_init_errata(dispc);
+
 	dispc->fourccs = devm_kcalloc(dev, ARRAY_SIZE(dispc_color_formats),
 				      sizeof(*dispc->fourccs), GFP_KERNEL);
 	if (!dispc->fourccs)
 		return -ENOMEM;
 
 	num_fourccs = 0;
-	for (i = 0; i < ARRAY_SIZE(dispc_color_formats); ++i)
+	for (i = 0; i < ARRAY_SIZE(dispc_color_formats); ++i) {
+		if (dispc->errata.i2000 &&
+		    dispc_fourcc_is_yuv(dispc_color_formats[i].fourcc)) {
+			continue;
+		}
 		dispc->fourccs[num_fourccs++] = dispc_color_formats[i].fourcc;
+	}
 
 	dispc->num_fourccs = num_fourccs;
-	dispc->tidss = tidss;
-	dispc->dev = dev;
-	dispc->feat = feat;
 
 	dispc_common_regmap = dispc->feat->common_regs;
 

drivers/gpu/drm/tidss/tidss_dispc.h

@@ -46,6 +46,10 @@ struct dispc_features_scaling {
 	u32 xinc_max;
 };
 
+struct dispc_errata {
+	bool i2000; /* DSS Does Not Support YUV Pixel Data Formats */
+};
+
 enum dispc_vp_bus_type {
 	DISPC_VP_DPI,		/* DPI output */
 	DISPC_VP_OLDI,		/* OLDI (LVDS) output */