phy: dphy: Add configuration helpers

The MIPI D-PHY spec defines default values and boundaries for most of the
parameters it defines. Introduce helpers to help drivers get meaningful
values based on their current parameters, and validate the boundaries of
these parameters if needed.

These helpers and header are taken from Linux commit 9123e3a74ec7 ("Linux 5.9-rc1").

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

3 files changed, 167 insertions, 0 deletions

diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig
index ab638f0..425737c 100644
--- a/drivers/phy/Kconfig
+++ b/drivers/phy/Kconfig
@@ -59,6 +59,11 @@ config SPL_NOP_PHY
 	  This is useful when a driver uses the PHY framework but no real PHY
 	  hardware exists.
 
+config MIPI_DPHY_HELPERS
+	bool "MIPI D-PHY support helpers"
+	help
+	  Provides a number of helpers a core functions for MIPI D-PHY drivers.
+
 config BCM6318_USBH_PHY
 	bool "BCM6318 USBH PHY support"
 	depends on PHY && ARCH_BMIPS
diff --git a/drivers/phy/Makefile b/drivers/phy/Makefile
index 6b3761b..7b81ff7 100644
--- a/drivers/phy/Makefile
+++ b/drivers/phy/Makefile
@@ -5,6 +5,7 @@
 
 obj-$(CONFIG_$(SPL_)PHY) += phy-uclass.o
 obj-$(CONFIG_$(SPL_)NOP_PHY) += nop-phy.o
+obj-$(CONFIG_MIPI_DPHY_HELPERS) += phy-core-mipi-dphy.o
 obj-$(CONFIG_BCM6318_USBH_PHY) += bcm6318-usbh-phy.o
 obj-$(CONFIG_BCM6348_USBH_PHY) += bcm6348-usbh-phy.o
 obj-$(CONFIG_BCM6358_USBH_PHY) += bcm6358-usbh-phy.o
diff --git a/drivers/phy/phy-core-mipi-dphy.c b/drivers/phy/phy-core-mipi-dphy.c
new file mode 100644
index 0000000..ba5f648
--- /dev/null
+++ b/drivers/phy/phy-core-mipi-dphy.c
@@ -0,0 +1,161 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2013 NVIDIA Corporation
+ * Copyright (C) 2018 Cadence Design Systems Inc.
+ */
+
+#include <common.h>
+#include <div64.h>
+
+#include <phy-mipi-dphy.h>
+
+#define PSEC_PER_SEC	1000000000000LL
+
+/*
+ * Minimum D-PHY timings based on MIPI D-PHY specification. Derived
+ * from the valid ranges specified in Section 6.9, Table 14, Page 41
+ * of the D-PHY specification (v2.1).
+ */
+int phy_mipi_dphy_get_default_config(unsigned long pixel_clock,
+				     unsigned int bpp,
+				     unsigned int lanes,
+				     struct phy_configure_opts_mipi_dphy *cfg)
+{
+	unsigned long long hs_clk_rate;
+	unsigned long long ui;
+
+	if (!cfg)
+		return -EINVAL;
+
+	hs_clk_rate = pixel_clock * bpp;
+	do_div(hs_clk_rate, lanes);
+
+	ui = ALIGN(PSEC_PER_SEC, hs_clk_rate);
+	do_div(ui, hs_clk_rate);
+
+	cfg->clk_miss = 0;
+	cfg->clk_post = 60000 + 52 * ui;
+	cfg->clk_pre = 8000;
+	cfg->clk_prepare = 38000;
+	cfg->clk_settle = 95000;
+	cfg->clk_term_en = 0;
+	cfg->clk_trail = 60000;
+	cfg->clk_zero = 262000;
+	cfg->d_term_en = 0;
+	cfg->eot = 0;
+	cfg->hs_exit = 100000;
+	cfg->hs_prepare = 40000 + 4 * ui;
+	cfg->hs_zero = 105000 + 6 * ui;
+	cfg->hs_settle = 85000 + 6 * ui;
+	cfg->hs_skip = 40000;
+
+	/*
+	 * The MIPI D-PHY specification (Section 6.9, v1.2, Table 14, Page 40)
+	 * contains this formula as:
+	 *
+	 *     T_HS-TRAIL = max(n * 8 * ui, 60 + n * 4 * ui)
+	 *
+	 * where n = 1 for forward-direction HS mode and n = 4 for reverse-
+	 * direction HS mode. There's only one setting and this function does
+	 * not parameterize on anything other that ui, so this code will
+	 * assumes that reverse-direction HS mode is supported and uses n = 4.
+	 */
+	cfg->hs_trail = max(4 * 8 * ui, 60000 + 4 * 4 * ui);
+
+	cfg->init = 100;
+	cfg->lpx = 60000;
+	cfg->ta_get = 5 * cfg->lpx;
+	cfg->ta_go = 4 * cfg->lpx;
+	cfg->ta_sure = 2 * cfg->lpx;
+	cfg->wakeup = 1000;
+
+	cfg->hs_clk_rate = hs_clk_rate;
+	cfg->lanes = lanes;
+
+	return 0;
+}
+
+/*
+ * Validate D-PHY configuration according to MIPI D-PHY specification
+ * (v1.2, Section Section 6.9 "Global Operation Timing Parameters").
+ */
+int phy_mipi_dphy_config_validate(struct phy_configure_opts_mipi_dphy *cfg)
+{
+	unsigned long long ui;
+
+	if (!cfg)
+		return -EINVAL;
+
+	ui = ALIGN(PSEC_PER_SEC, cfg->hs_clk_rate);
+	do_div(ui, cfg->hs_clk_rate);
+
+	if (cfg->clk_miss > 60000)
+		return -EINVAL;
+
+	if (cfg->clk_post < (60000 + 52 * ui))
+		return -EINVAL;
+
+	if (cfg->clk_pre < 8000)
+		return -EINVAL;
+
+	if (cfg->clk_prepare < 38000 || cfg->clk_prepare > 95000)
+		return -EINVAL;
+
+	if (cfg->clk_settle < 95000 || cfg->clk_settle > 300000)
+		return -EINVAL;
+
+	if (cfg->clk_term_en > 38000)
+		return -EINVAL;
+
+	if (cfg->clk_trail < 60000)
+		return -EINVAL;
+
+	if ((cfg->clk_prepare + cfg->clk_zero) < 300000)
+		return -EINVAL;
+
+	if (cfg->d_term_en > (35000 + 4 * ui))
+		return -EINVAL;
+
+	if (cfg->eot > (105000 + 12 * ui))
+		return -EINVAL;
+
+	if (cfg->hs_exit < 100000)
+		return -EINVAL;
+
+	if (cfg->hs_prepare < (40000 + 4 * ui) ||
+	    cfg->hs_prepare > (85000 + 6 * ui))
+		return -EINVAL;
+
+	if ((cfg->hs_prepare + cfg->hs_zero) < (145000 + 10 * ui))
+		return -EINVAL;
+
+	if ((cfg->hs_settle < (85000 + 6 * ui)) ||
+	    (cfg->hs_settle > (145000 + 10 * ui)))
+		return -EINVAL;
+
+	if (cfg->hs_skip < 40000 || cfg->hs_skip > (55000 + 4 * ui))
+		return -EINVAL;
+
+	if (cfg->hs_trail < max(8 * ui, 60000 + 4 * ui))
+		return -EINVAL;
+
+	if (cfg->init < 100)
+		return -EINVAL;
+
+	if (cfg->lpx < 50000)
+		return -EINVAL;
+
+	if (cfg->ta_get != (5 * cfg->lpx))
+		return -EINVAL;
+
+	if (cfg->ta_go != (4 * cfg->lpx))
+		return -EINVAL;
+
+	if (cfg->ta_sure < cfg->lpx || cfg->ta_sure > (2 * cfg->lpx))
+		return -EINVAL;
+
+	if (cfg->wakeup < 1000)
+		return -EINVAL;
+
+	return 0;
+}