Re: [PATCH] phy: dphy: Correct clk_pre parameter
From: Andrzej Hajda
Date: Tue Jan 18 2022 - 04:25:10 EST
Hi,
On 18.01.2022 03:59, Liu Ying wrote:
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@xxxxxxxxx>
Cc: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
Cc: Robert Foss <robert.foss@xxxxxxxxxx>
Cc: Laurent Pinchart <Laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: Jonas Karlman <jonas@xxxxxxxxx>
Cc: Jernej Skrabec <jernej.skrabec@xxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Kishon Vijay Abraham I <kishon@xxxxxx>
Cc: Vinod Koul <vkoul@xxxxxxxxxx>
Cc: Kevin Hilman <khilman@xxxxxxxxxxxx>
Cc: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
Cc: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
Cc: Heiko Stuebner <heiko@xxxxxxxxx>
Cc: Maxime Ripard <mripard@xxxxxxxxxx>
Cc: Guido Günther <agx@xxxxxxxxxxx>
Tested-by: Liu Ying <victor.liu@xxxxxxx> # RM67191 DSI panel on i.MX8mq EVK
Signed-off-by: Liu Ying <victor.liu@xxxxxxx>
---
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);
I have some doubts here. According to specs:
UI - duration of any HS state on the Clock Lane,
TxByteClkHS - exactly 1/8 the High-Speed(HS) bit rate
I'd like to emphasize "BIT RATE" above (not clock rate).
In such case I would expect that ui2bc would take into account number of
lanes:
byte clock cycles = div_round_up(ui * dsi->lanes, 8)
So in case of one lane we need 8 ticks to get byte, and in case of 4
lanes 2 ticks are enough.
Am I correct, or I've missed sth?
}
/*
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
Do we need to define it? I guess it is just BITS_PER_BYTE.
Regards
Andrzej
+
/**
* 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;