phy: dphy: Correct clk_pre parameter

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.

So, let's fix the dphy core driver to correctly reflect the T-CLK-PRE
parameter's 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, BITS_PER_BYTE), 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: 2ed8699 ("phy: Add MIPI D-PHY configuration options")
Tested-by: Liu Ying <[email protected]> # RM67191 DSI panel on i.MX8mq EVK
Reviewed-by: Andrzej Hajda <[email protected]>
Reviewed-by: Neil Armstrong <[email protected]> # for phy-meson-axg-mipi-dphy.c
Tested-by: Neil Armstrong <[email protected]> # for phy-meson-axg-mipi-dphy.c
Tested-by: Guido Günther <[email protected]> # Librem 5 (imx8mq) with it's rather picky panel
Reviewed-by: Laurent Pinchart <[email protected]>
Signed-off-by: Liu Ying <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

Author: Liu Ying

drivers/gpu/drm/bridge/nwl-dsi.c

@@ -7,6 +7,7 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/bits.h>
 #include <linux/clk.h>
 #include <linux/irq.h>
 #include <linux/math64.h>
@@ -196,12 +197,9 @@ 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(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, BITS_PER_BYTE);
 }
 
 /*
@@ -232,12 +230,12 @@ static int nwl_dsi_config_host(struct nwl_dsi *dsi)
 	}
 
 	/* values in byte clock cycles */
-	cycles = ui2bc(dsi, cfg->clk_pre);
+	cycles = ui2bc(cfg->clk_pre);
 	DRM_DEV_DEBUG_DRIVER(dsi->dev, "cfg_t_pre: 0x%x\n", cycles);
 	nwl_dsi_write(dsi, NWL_DSI_CFG_T_PRE, cycles);
 	cycles = ps2bc(dsi, cfg->lpx + cfg->clk_prepare + cfg->clk_zero);
 	DRM_DEV_DEBUG_DRIVER(dsi->dev, "cfg_tx_gap (pre): 0x%x\n", cycles);
-	cycles += ui2bc(dsi, cfg->clk_pre);
+	cycles += ui2bc(cfg->clk_pre);
 	DRM_DEV_DEBUG_DRIVER(dsi->dev, "cfg_t_post: 0x%x\n", cycles);
 	nwl_dsi_write(dsi, NWL_DSI_CFG_T_POST, cycles);
 	cycles = ps2bc(dsi, cfg->hs_exit);

drivers/phy/amlogic/phy-meson-axg-mipi-dphy.c

@@ -9,6 +9,7 @@
 
 #include <linux/bitfield.h>
 #include <linux/bitops.h>
+#include <linux/bits.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/io.h>
@@ -250,7 +251,7 @@ 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, BITS_PER_BYTE));
 
 	regmap_write(priv->regmap, MIPI_DSI_HS_TIM,
 		     DIV_ROUND_UP(priv->config.hs_exit, temp) |

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)

drivers/phy/rockchip/phy-rockchip-inno-dsidphy.c

@@ -5,6 +5,7 @@
  * Author: Wyon Bi <[email protected]>
  */
 
+#include <linux/bits.h>
 #include <linux/kernel.h>
 #include <linux/clk.h>
 #include <linux/iopoll.h>
@@ -364,7 +365,7 @@ 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, BITS_PER_BYTE);
 
 	/*
 	 * The value of counter for HS Tlpx Time