drm/mcde: Support DPI output

This implements support for DPI output using the port node
in the device tree to connect a DPI LCD display to the
MCDE. The block also supports TV-out but we leave that
for another day when we have a hardware using it.

We implement parsing and handling of the "port" node,
and follow that to the DPI endpoint.

The clock divider used by the MCDE to divide down the
"lcdclk" (this has been designed for TV-like frequencies)
is represented by an ordinary clock provider internally
in the MCDE. This idea was inspired by the PL111 solution
by Eric Anholt: the divider also works very similar to
the Pl111 clock divider.

We take care to clear up some errors regarding the number
of available formatters and their type. We have 6 DSI
formatters and 2 DPI formatters.

Tested on the Samsung GT-I9070 Janice mobile phone.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Stephan Gerhold <stephan@gerhold.net>
Cc: phone-devel@vger.kernel.org
Cc: upstreaming@lists.sr.ht
Link: https://patchwork.freedesktop.org/patch/msgid/20201112142925.2571179-2-linus.walleij@linaro.org

drivers/gpu/drm/mcde/Kconfig

@@ -4,6 +4,7 @@ config DRM_MCDE
 	depends on CMA
 	depends on ARM || COMPILE_TEST
 	depends on OF
+	depends on COMMON_CLK
 	select MFD_SYSCON
 	select DRM_MIPI_DSI
 	select DRM_BRIDGE

drivers/gpu/drm/mcde/Makefile

@@ -1,3 +1,3 @@
-mcde_drm-y +=	mcde_drv.o mcde_dsi.o mcde_display.o
+mcde_drm-y +=	mcde_drv.o mcde_dsi.o mcde_clk_div.o mcde_display.o
 
 obj-$(CONFIG_DRM_MCDE) += mcde_drm.o

drivers/gpu/drm/mcde/mcde_clk_div.c

@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/clk-provider.h>
+#include <linux/regulator/consumer.h>
+
+#include "mcde_drm.h"
+#include "mcde_display_regs.h"
+
+/* The MCDE internal clock dividers for FIFO A and B */
+struct mcde_clk_div {
+	struct clk_hw hw;
+	struct mcde *mcde;
+	u32 cr;
+	u32 cr_div;
+};
+
+static int mcde_clk_div_enable(struct clk_hw *hw)
+{
+	struct mcde_clk_div *cdiv = container_of(hw, struct mcde_clk_div, hw);
+	struct mcde *mcde = cdiv->mcde;
+	u32 val;
+
+	spin_lock(&mcde->fifo_crx1_lock);
+	val = readl(mcde->regs + cdiv->cr);
+	/*
+	 * Select the PLL72 (LCD) clock as parent
+	 * FIXME: implement other parents.
+	 */
+	val &= ~MCDE_CRX1_CLKSEL_MASK;
+	val |= MCDE_CRX1_CLKSEL_CLKPLL72 << MCDE_CRX1_CLKSEL_SHIFT;
+	/* Internal clock */
+	val |= MCDE_CRA1_CLKTYPE_TVXCLKSEL1;
+
+	/* Clear then set the divider */
+	val &= ~(MCDE_CRX1_BCD | MCDE_CRX1_PCD_MASK);
+	val |= cdiv->cr_div;
+
+	writel(val, mcde->regs + cdiv->cr);
+	spin_unlock(&mcde->fifo_crx1_lock);
+
+	return 0;
+}
+
+static int mcde_clk_div_choose_div(struct clk_hw *hw, unsigned long rate,
+				   unsigned long *prate, bool set_parent)
+{
+	int best_div = 1, div;
+	struct clk_hw *parent = clk_hw_get_parent(hw);
+	unsigned long best_prate = 0;
+	unsigned long best_diff = ~0ul;
+	int max_div = (1 << MCDE_CRX1_PCD_BITS) - 1;
+
+	for (div = 1; div < max_div; div++) {
+		unsigned long this_prate, div_rate, diff;
+
+		if (set_parent)
+			this_prate = clk_hw_round_rate(parent, rate * div);
+		else
+			this_prate = *prate;
+		div_rate = DIV_ROUND_UP_ULL(this_prate, div);
+		diff = abs(rate - div_rate);
+
+		if (diff < best_diff) {
+			best_div = div;
+			best_diff = diff;
+			best_prate = this_prate;
+		}
+	}
+
+	*prate = best_prate;
+	return best_div;
+}
+
+static long mcde_clk_div_round_rate(struct clk_hw *hw, unsigned long rate,
+				     unsigned long *prate)
+{
+	int div = mcde_clk_div_choose_div(hw, rate, prate, true);
+
+	return DIV_ROUND_UP_ULL(*prate, div);
+}
+
+static unsigned long mcde_clk_div_recalc_rate(struct clk_hw *hw,
+					       unsigned long prate)
+{
+	struct mcde_clk_div *cdiv = container_of(hw, struct mcde_clk_div, hw);
+	struct mcde *mcde = cdiv->mcde;
+	u32 cr;
+	int div;
+
+	/*
+	 * If the MCDE is not powered we can't access registers.
+	 * It will come up with 0 in the divider register bits, which
+	 * means "divide by 2".
+	 */
+	if (!regulator_is_enabled(mcde->epod))
+		return DIV_ROUND_UP_ULL(prate, 2);
+
+	cr = readl(mcde->regs + cdiv->cr);
+	if (cr & MCDE_CRX1_BCD)
+		return prate;
+
+	/* 0 in the PCD means "divide by 2", 1 means "divide by 3" etc */
+	div = cr & MCDE_CRX1_PCD_MASK;
+	div += 2;
+
+	return DIV_ROUND_UP_ULL(prate, div);
+}
+
+static int mcde_clk_div_set_rate(struct clk_hw *hw, unsigned long rate,
+				  unsigned long prate)
+{
+	struct mcde_clk_div *cdiv = container_of(hw, struct mcde_clk_div, hw);
+	int div = mcde_clk_div_choose_div(hw, rate, &prate, false);
+	u32 cr = 0;
+
+	/*
+	 * We cache the CR bits to set the divide in the state so that
+	 * we can call this before we can even write to the hardware.
+	 */
+	if (div == 1) {
+		/* Bypass clock divider */
+		cr |= MCDE_CRX1_BCD;
+	} else {
+		div -= 2;
+		cr |= div & MCDE_CRX1_PCD_MASK;
+	}
+	cdiv->cr_div = cr;
+
+	return 0;
+}
+
+static const struct clk_ops mcde_clk_div_ops = {
+	.enable = mcde_clk_div_enable,
+	.recalc_rate = mcde_clk_div_recalc_rate,
+	.round_rate = mcde_clk_div_round_rate,
+	.set_rate = mcde_clk_div_set_rate,
+};
+
+int mcde_init_clock_divider(struct mcde *mcde)
+{
+	struct device *dev = mcde->dev;
+	struct mcde_clk_div *fifoa;
+	struct mcde_clk_div *fifob;
+	const char *parent_name;
+	struct clk_init_data fifoa_init = {
+		.name = "fifoa",
+		.ops = &mcde_clk_div_ops,
+		.parent_names = &parent_name,
+		.num_parents = 1,
+		.flags = CLK_SET_RATE_PARENT,
+	};
+	struct clk_init_data fifob_init = {
+		.name = "fifob",
+		.ops = &mcde_clk_div_ops,
+		.parent_names = &parent_name,
+		.num_parents = 1,
+		.flags = CLK_SET_RATE_PARENT,
+	};
+	int ret;
+
+	spin_lock_init(&mcde->fifo_crx1_lock);
+	parent_name = __clk_get_name(mcde->lcd_clk);
+
+	/* Allocate 2 clocks */
+	fifoa = devm_kzalloc(dev, sizeof(*fifoa), GFP_KERNEL);
+	if (!fifoa)
+		return -ENOMEM;
+	fifob = devm_kzalloc(dev, sizeof(*fifob), GFP_KERNEL);
+	if (!fifob)
+		return -ENOMEM;
+
+	fifoa->mcde = mcde;
+	fifoa->cr = MCDE_CRA1;
+	fifoa->hw.init = &fifoa_init;
+	ret = devm_clk_hw_register(dev, &fifoa->hw);
+	if (ret) {
+		dev_err(dev, "error registering FIFO A clock divider\n");
+		return ret;
+	}
+	mcde->fifoa_clk = fifoa->hw.clk;
+
+	fifob->mcde = mcde;
+	fifob->cr = MCDE_CRB1;
+	fifob->hw.init = &fifob_init;
+	ret = devm_clk_hw_register(dev, &fifob->hw);
+	if (ret) {
+		dev_err(dev, "error registering FIFO B clock divider\n");
+		return ret;
+	}
+	mcde->fifob_clk = fifob->hw.clk;
+
+	return 0;
+}