[PATCH] phy: dphy: Correct clk_pre parameter

[Liu Ying <victor.liu@nxp.com>]

The D-PHY specification (v1.2) explicitly mentions that the T-CLK-PRE
parameter's unit is Unit Interval(UI) and the minimum value is 8.  Also,
kernel doc of the 'clk_pre' member of struct phy_configure_opts_mipi_dphy
mentions that it should be in UI.  However, the dphy core driver wrongly
sets 'clk_pre' to 8000, which seems to hint that it's in picoseconds.
And, the kernel doc of the 'clk_pre' member wrongly says the minimum value
is '8 UI', instead of 8.

So, let's fix both the dphy core driver and the kernel doc of the 'clk_pre'
member to correctly reflect the T-CLK-PRE parameter's unit and the minimum
value according to the D-PHY specification.

I'm assuming that all impacted custom drivers shall program values in
TxByteClkHS cycles into hardware for the T-CLK-PRE parameter.  The D-PHY
specification mentions that the frequency of TxByteClkHS is exactly 1/8
the High-Speed(HS) bit rate(each HS bit consumes one UI).  So, relevant
custom driver code is changed to program those values as
DIV_ROUND_UP(cfg->clk_pre, MIPI_DPHY_UI_PER_TXBYTECLKHS_PERIOD), then.

Note that I've only tested the patch with RM67191 DSI panel on i.MX8mq EVK.
Help is needed to test with other i.MX8mq, Meson and Rockchip platforms,
as I don't have the hardwares.

Fixes: 2ed869990e14 ("phy: Add MIPI D-PHY configuration options")
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Guido Günther <agx@sigxcpu.org>
Tested-by: Liu Ying <victor.liu@nxp.com> # RM67191 DSI panel on i.MX8mq EVK
Signed-off-by: Liu Ying <victor.liu@nxp.com>
---
 drivers/gpu/drm/bridge/nwl-dsi.c                 | 7 ++-----
 drivers/phy/amlogic/phy-meson-axg-mipi-dphy.c    | 3 ++-
 drivers/phy/phy-core-mipi-dphy.c                 | 4 ++--
 drivers/phy/rockchip/phy-rockchip-inno-dsidphy.c | 3 ++-
 include/linux/phy/phy-mipi-dphy.h                | 4 +++-
 5 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/bridge/nwl-dsi.c b/drivers/gpu/drm/bridge/nwl-dsi.c
index a7389a0facfb..f1fdcdf763ee 100644
--- a/drivers/gpu/drm/bridge/nwl-dsi.c
+++ b/drivers/gpu/drm/bridge/nwl-dsi.c
@@ -196,12 +196,9 @@ static u32 ps2bc(struct nwl_dsi *dsi, unsigned long long ps)
 /*
  * ui2bc - UI time periods to byte clock cycles
  */
-static u32 ui2bc(struct nwl_dsi *dsi, unsigned long long ui)
+static u32 ui2bc(struct nwl_dsi *dsi, unsigned int ui)
 {
-	u32 bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
-
-	return DIV64_U64_ROUND_UP(ui * dsi->lanes,
-				  dsi->mode.clock * 1000 * bpp);
+	return DIV_ROUND_UP(ui, MIPI_DPHY_UI_PER_TXBYTECLKHS_PERIOD);
 }
 
 /*
diff --git a/drivers/phy/amlogic/phy-meson-axg-mipi-dphy.c b/drivers/phy/amlogic/phy-meson-axg-mipi-dphy.c
index cd2332bf0e31..8a818cdb7606 100644
--- a/drivers/phy/amlogic/phy-meson-axg-mipi-dphy.c
+++ b/drivers/phy/amlogic/phy-meson-axg-mipi-dphy.c
@@ -250,7 +250,8 @@ static int phy_meson_axg_mipi_dphy_power_on(struct phy *phy)
 		     (DIV_ROUND_UP(priv->config.clk_zero, temp) << 16) |
 		     (DIV_ROUND_UP(priv->config.clk_prepare, temp) << 24));
 	regmap_write(priv->regmap, MIPI_DSI_CLK_TIM1,
-		     DIV_ROUND_UP(priv->config.clk_pre, temp));
+		     DIV_ROUND_UP(priv->config.clk_pre,
+				  MIPI_DPHY_UI_PER_TXBYTECLKHS_PERIOD));
 
 	regmap_write(priv->regmap, MIPI_DSI_HS_TIM,
 		     DIV_ROUND_UP(priv->config.hs_exit, temp) |
diff --git a/drivers/phy/phy-core-mipi-dphy.c b/drivers/phy/phy-core-mipi-dphy.c
index 288c9c67aa74..ccb4045685cd 100644
--- a/drivers/phy/phy-core-mipi-dphy.c
+++ b/drivers/phy/phy-core-mipi-dphy.c
@@ -36,7 +36,7 @@ int phy_mipi_dphy_get_default_config(unsigned long pixel_clock,
 
 	cfg->clk_miss = 0;
 	cfg->clk_post = 60000 + 52 * ui;
-	cfg->clk_pre = 8000;
+	cfg->clk_pre = 8;
 	cfg->clk_prepare = 38000;
 	cfg->clk_settle = 95000;
 	cfg->clk_term_en = 0;
@@ -97,7 +97,7 @@ int phy_mipi_dphy_config_validate(struct phy_configure_opts_mipi_dphy *cfg)
 	if (cfg->clk_post < (60000 + 52 * ui))
 		return -EINVAL;
 
-	if (cfg->clk_pre < 8000)
+	if (cfg->clk_pre < 8)
 		return -EINVAL;
 
 	if (cfg->clk_prepare < 38000 || cfg->clk_prepare > 95000)
diff --git a/drivers/phy/rockchip/phy-rockchip-inno-dsidphy.c b/drivers/phy/rockchip/phy-rockchip-inno-dsidphy.c
index 347dc79a18c1..67b0a17be7e3 100644
--- a/drivers/phy/rockchip/phy-rockchip-inno-dsidphy.c
+++ b/drivers/phy/rockchip/phy-rockchip-inno-dsidphy.c
@@ -364,7 +364,8 @@ static void inno_dsidphy_mipi_mode_enable(struct inno_dsidphy *inno)
 	 * The value of counter for HS Tclk-pre
 	 * Tclk-pre = Tpin_txbyteclkhs * value
 	 */
-	clk_pre = DIV_ROUND_UP(cfg->clk_pre, t_txbyteclkhs);
+	clk_pre = DIV_ROUND_UP(cfg->clk_pre,
+			       MIPI_DPHY_UI_PER_TXBYTECLKHS_PERIOD);
 
 	/*
 	 * The value of counter for HS Tlpx Time
diff --git a/include/linux/phy/phy-mipi-dphy.h b/include/linux/phy/phy-mipi-dphy.h
index a877ffee845d..ab1f736fbcd3 100644
--- a/include/linux/phy/phy-mipi-dphy.h
+++ b/include/linux/phy/phy-mipi-dphy.h
@@ -6,6 +6,8 @@
 #ifndef __PHY_MIPI_DPHY_H_
 #define __PHY_MIPI_DPHY_H_
 
+#define MIPI_DPHY_UI_PER_TXBYTECLKHS_PERIOD	8
+
 /**
  * struct phy_configure_opts_mipi_dphy - MIPI D-PHY configuration set
  *
@@ -42,7 +44,7 @@ struct phy_configure_opts_mipi_dphy {
 	 * the transmitter prior to any associated Data Lane beginning
 	 * the transition from LP to HS mode.
 	 *
-	 * Minimum value: 8 UI
+	 * Minimum value: 8
 	 */
 	unsigned int		clk_pre;
 
-- 
2.25.1