DRM: Armada: Add Armada DRM driver

This patch adds support for the pair of LCD controllers on the Marvell
Armada 510 SoCs.  This driver supports:
- multiple contiguous scanout buffers for video and graphics
- shm backed cacheable buffer objects for X pixmaps for Vivante GPU
  acceleration
- dual lcd0 and lcd1 crt operation
- video overlay on each LCD crt via DRM planes
- page flipping of the main scanout buffers
- DRM prime for buffer export/import

This driver is trivial to extend to other Armada SoCs.

Included in this commit is the core driver with no output support; output
support is platform and encoder driver dependent.

Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/gpu/drm/Kconfig

@@ -225,6 +225,8 @@ source "drivers/gpu/drm/mgag200/Kconfig"
 
 source "drivers/gpu/drm/cirrus/Kconfig"
 
+source "drivers/gpu/drm/armada/Kconfig"
+
 source "drivers/gpu/drm/rcar-du/Kconfig"
 
 source "drivers/gpu/drm/shmobile/Kconfig"

drivers/gpu/drm/Makefile

@@ -49,6 +49,7 @@ obj-$(CONFIG_DRM_EXYNOS) +=exynos/
 obj-$(CONFIG_DRM_GMA500) += gma500/
 obj-$(CONFIG_DRM_UDL) += udl/
 obj-$(CONFIG_DRM_AST) += ast/
+obj-$(CONFIG_DRM_ARMADA) += armada/
 obj-$(CONFIG_DRM_RCAR_DU) += rcar-du/
 obj-$(CONFIG_DRM_SHMOBILE) +=shmobile/
 obj-$(CONFIG_DRM_OMAP)	+= omapdrm/

drivers/gpu/drm/armada/Kconfig

@@ -0,0 +1,15 @@
+config DRM_ARMADA
+	tristate "DRM support for Marvell Armada SoCs"
+	depends on DRM && HAVE_CLK
+	select FB_CFB_FILLRECT
+	select FB_CFB_COPYAREA
+	select FB_CFB_IMAGEBLIT
+	select DRM_KMS_HELPER
+	help
+	  Support the "LCD" controllers found on the Marvell Armada 510
+	  devices.  There are two controllers on the device, each controller
+	  supports graphics and video overlays.
+
+	  This driver provides no built-in acceleration; acceleration is
+	  performed by other IP found on the SoC.  This driver provides
+	  kernel mode setting and buffer management to userspace.

drivers/gpu/drm/armada/Makefile

@@ -0,0 +1,7 @@
+armada-y	:= armada_crtc.o armada_drv.o armada_fb.o armada_fbdev.o \
+		   armada_gem.o armada_output.o armada_overlay.o \
+		   armada_slave.o
+armada-y	+= armada_510.o
+armada-$(CONFIG_DEBUG_FS) += armada_debugfs.o
+
+obj-$(CONFIG_DRM_ARMADA) := armada.o

drivers/gpu/drm/armada/armada_510.c

@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) 2012 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Armada 510 (aka Dove) variant support
+ */
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <drm/drmP.h>
+#include <drm/drm_crtc_helper.h>
+#include "armada_crtc.h"
+#include "armada_drm.h"
+#include "armada_hw.h"
+
+static int armada510_init(struct armada_private *priv, struct device *dev)
+{
+	priv->extclk[0] = devm_clk_get(dev, "ext_ref_clk_1");
+
+	if (IS_ERR(priv->extclk[0]) && PTR_ERR(priv->extclk[0]) == -ENOENT)
+		priv->extclk[0] = ERR_PTR(-EPROBE_DEFER);
+
+	return PTR_RET(priv->extclk[0]);
+}
+
+static int armada510_crtc_init(struct armada_crtc *dcrtc)
+{
+	/* Lower the watermark so to eliminate jitter at higher bandwidths */
+	armada_updatel(0x20, (1 << 11) | 0xff, dcrtc->base + LCD_CFG_RDREG4F);
+	return 0;
+}
+
+/*
+ * Armada510 specific SCLK register selection.
+ * This gets called with sclk = NULL to test whether the mode is
+ * supportable, and again with sclk != NULL to set the clocks up for
+ * that.  The former can return an error, but the latter is expected
+ * not to.
+ *
+ * We currently are pretty rudimentary here, always selecting
+ * EXT_REF_CLK_1 for LCD0 and erroring LCD1.  This needs improvement!
+ */
+static int armada510_crtc_compute_clock(struct armada_crtc *dcrtc,
+	const struct drm_display_mode *mode, uint32_t *sclk)
+{
+	struct armada_private *priv = dcrtc->crtc.dev->dev_private;
+	struct clk *clk = priv->extclk[0];
+	int ret;
+
+	if (dcrtc->num == 1)
+		return -EINVAL;
+
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	if (dcrtc->clk != clk) {
+		ret = clk_prepare_enable(clk);
+		if (ret)
+			return ret;
+		dcrtc->clk = clk;
+	}
+
+	if (sclk) {
+		uint32_t rate, ref, div;
+
+		rate = mode->clock * 1000;
+		ref = clk_round_rate(clk, rate);
+		div = DIV_ROUND_UP(ref, rate);
+		if (div < 1)
+			div = 1;
+
+		clk_set_rate(clk, ref);
+		*sclk = div | SCLK_510_EXTCLK1;
+	}
+
+	return 0;
+}
+
+const struct armada_variant armada510_ops = {
+	.has_spu_adv_reg = true,
+	.init = armada510_init,
+	.crtc_init = armada510_crtc_init,
+	.crtc_compute_clock = armada510_crtc_compute_clock,
+};