video: Add simple driver for ST-Ericsson MCDE with pre-configured display

The U-Boot port for ST-Ericsson Ux500 is currently only used on the
"stemmy" board, where U-Boot runs after firmware that already sets up
a boot splash screen. This means that the display is already on
and we can just continue using it for U-Boot.

Add a simple driver that simplifies this by reading the display
configuration (e.g. screen size, bpp) from the hardware registers.

It also checks the configured "source synchronization" - for some
displays (usually DSI command mode displays) we need to explicitly
trigger a software sync. This is done through the video_sync()
callback that triggers the sync and wait for completion.

Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

drivers/video/Kconfig

@@ -854,6 +854,18 @@ config VIDEO_DT_SIMPLEFB
 	  The video output is initialized by U-Boot, and kept by the
 	  kernel.
 
+config VIDEO_MCDE_SIMPLE
+	bool "Simple driver for ST-Ericsson MCDE with preconfigured display"
+	depends on DM_VIDEO
+	help
+	  Enables a simple display driver for ST-Ericsson MCDE
+	  (Multichannel Display Engine), which reads the configuration from
+	  the MCDE registers.
+
+	  This driver assumes that the display hardware has been initialized
+	  before u-boot starts, and u-boot will simply render to the pre-
+	  allocated frame buffer surface.
+
 config OSD
 	bool "Enable OSD support"
 	depends on DM

drivers/video/Makefile

@@ -58,6 +58,7 @@ obj-$(CONFIG_VIDEO_LCD_ORISETECH_OTM8009A) += orisetech_otm8009a.o
 obj-$(CONFIG_VIDEO_LCD_RAYDIUM_RM68200) += raydium-rm68200.o
 obj-$(CONFIG_VIDEO_LCD_SSD2828) += ssd2828.o
 obj-$(CONFIG_VIDEO_LCD_TDO_TL070WSH30) += tdo-tl070wsh30.o
+obj-$(CONFIG_VIDEO_MCDE_SIMPLE) += mcde_simple.o
 obj-${CONFIG_VIDEO_MESON} += meson/
 obj-${CONFIG_VIDEO_MIPI_DSI} += mipi_dsi.o
 obj-$(CONFIG_VIDEO_MVEBU) += mvebu_lcd.o

drivers/video/mcde_simple.c

@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright (C) 2019 Stephan Gerhold */
+
+#include <common.h>
+#include <dm.h>
+#include <log.h>
+#include <video.h>
+#include <asm/io.h>
+#include <linux/bitfield.h>
+#include <linux/iopoll.h>
+
+#define MCDE_EXTSRC0A0			0x200
+#define MCDE_EXTSRC0CONF		0x20C
+#define MCDE_EXTSRC0CONF_BPP		GENMASK(11, 8)
+#define MCDE_OVL0CONF			0x404
+#define MCDE_OVL0CONF_PPL		GENMASK(10, 0)
+#define MCDE_OVL0CONF_LPF		GENMASK(26, 16)
+#define MCDE_CHNL0SYNCHMOD		0x608
+#define MCDE_CHNL0SYNCHMOD_SRC_SYNCH	GENMASK(1, 0)
+#define MCDE_CHNL0SYNCHSW		0x60C
+#define MCDE_CHNL0SYNCHSW_SW_TRIG	BIT(0)
+#define MCDE_CRA0			0x800
+#define MCDE_CRA0_FLOEN			BIT(0)
+
+#define MCDE_FLOW_COMPLETION_TIMEOUT	200000	/* us */
+
+enum mcde_bpp {
+	MCDE_EXTSRC0CONF_BPP_1BPP_PAL,
+	MCDE_EXTSRC0CONF_BPP_2BPP_PAL,
+	MCDE_EXTSRC0CONF_BPP_4BPP_PAL,
+	MCDE_EXTSRC0CONF_BPP_8BPP_PAL,
+	MCDE_EXTSRC0CONF_BPP_RGB444,
+	MCDE_EXTSRC0CONF_BPP_ARGB4444,
+	MCDE_EXTSRC0CONF_BPP_IRGB1555,
+	MCDE_EXTSRC0CONF_BPP_RGB565,
+	MCDE_EXTSRC0CONF_BPP_RGB888,
+	MCDE_EXTSRC0CONF_BPP_XRGB8888,
+	MCDE_EXTSRC0CONF_BPP_ARGB8888,
+	MCDE_EXTSRC0CONF_BPP_YCBCR422,
+};
+
+enum mcde_src_synch {
+	MCDE_CHNL0SYNCHMOD_SRC_SYNCH_HARDWARE,
+	MCDE_CHNL0SYNCHMOD_SRC_SYNCH_NO_SYNCH,
+	MCDE_CHNL0SYNCHMOD_SRC_SYNCH_SOFTWARE,
+};
+
+struct mcde_simple_priv {
+	fdt_addr_t base;
+	enum mcde_src_synch src_synch;
+};
+
+static int mcde_simple_probe(struct udevice *dev)
+{
+	struct mcde_simple_priv *priv = dev_get_priv(dev);
+	struct video_uc_plat *plat = dev_get_uclass_plat(dev);
+	struct video_priv *uc_priv = dev_get_uclass_priv(dev);
+	u32 val;
+
+	priv->base = dev_read_addr(dev);
+	if (priv->base == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	plat->base = readl(priv->base + MCDE_EXTSRC0A0);
+	if (!plat->base)
+		return -ENODEV;
+
+	val = readl(priv->base + MCDE_OVL0CONF);
+	uc_priv->xsize = FIELD_GET(MCDE_OVL0CONF_PPL, val);
+	uc_priv->ysize = FIELD_GET(MCDE_OVL0CONF_LPF, val);
+	uc_priv->rot = 0;
+
+	val = readl(priv->base + MCDE_EXTSRC0CONF);
+	switch (FIELD_GET(MCDE_EXTSRC0CONF_BPP, val)) {
+	case MCDE_EXTSRC0CONF_BPP_RGB565:
+		uc_priv->bpix = VIDEO_BPP16;
+		break;
+	case MCDE_EXTSRC0CONF_BPP_XRGB8888:
+	case MCDE_EXTSRC0CONF_BPP_ARGB8888:
+		uc_priv->bpix = VIDEO_BPP32;
+		break;
+	default:
+		printf("unsupported format: %#x\n", val);
+		return -EINVAL;
+	}
+
+	val = readl(priv->base + MCDE_CHNL0SYNCHMOD);
+	priv->src_synch = FIELD_GET(MCDE_CHNL0SYNCHMOD_SRC_SYNCH, val);
+
+	plat->size = uc_priv->xsize * uc_priv->ysize * VNBYTES(uc_priv->bpix);
+	debug("MCDE base: %#lx, xsize: %d, ysize: %d, bpp: %d\n",
+	      plat->base, uc_priv->xsize, uc_priv->ysize, VNBITS(uc_priv->bpix));
+
+	video_set_flush_dcache(dev, true);
+	return 0;
+}
+
+static int mcde_simple_video_sync(struct udevice *dev)
+{
+	struct mcde_simple_priv *priv = dev_get_priv(dev);
+	unsigned int val;
+
+	if (priv->src_synch != MCDE_CHNL0SYNCHMOD_SRC_SYNCH_SOFTWARE)
+		return 0;
+
+	/* Enable flow */
+	val = readl(priv->base + MCDE_CRA0);
+	val |= MCDE_CRA0_FLOEN;
+	writel(val, priv->base + MCDE_CRA0);
+
+	/* Trigger a software sync */
+	writel(MCDE_CHNL0SYNCHSW_SW_TRIG, priv->base + MCDE_CHNL0SYNCHSW);
+
+	/* Disable flow */
+	val = readl(priv->base + MCDE_CRA0);
+	val &= ~MCDE_CRA0_FLOEN;
+	writel(val, priv->base + MCDE_CRA0);
+
+	/* Wait for completion */
+	return readl_poll_timeout(priv->base + MCDE_CRA0, val,
+				  !(val & MCDE_CRA0_FLOEN),
+				  MCDE_FLOW_COMPLETION_TIMEOUT);
+}
+
+static struct video_ops mcde_simple_ops = {
+	.video_sync = mcde_simple_video_sync,
+};
+
+static const struct udevice_id mcde_simple_ids[] = {
+	{ .compatible = "ste,mcde" },
+	{ }
+};
+
+U_BOOT_DRIVER(mcde_simple) = {
+	.name		= "mcde_simple",
+	.id		= UCLASS_VIDEO,
+	.ops		= &mcde_simple_ops,
+	.of_match	= mcde_simple_ids,
+	.probe		= mcde_simple_probe,
+	.priv_auto	= sizeof(struct mcde_simple_priv),
+};