[PATCH 15/26] phy: dphy: Correct lpx parameter and its derivatives(ta_{get, go, sure})

Dario Binacchi
2024-09-13T09:59:36Z

From: Michael Trimarchi <michael@amarulasolutions.com>

Upstream linux commit 3153fa38e38af5.

According to the comment of the function phy_mipi_dphy_get_default_config(),
it uses minimum D-PHY timings based on MIPI D-PHY specification. They are
derived from the valid ranges specified in Section 6.9, Table 14, Page 41
of the D-PHY specification (v1.2). The table 14 explicitly mentions that
the minimum T-LPX parameter is 50 nanoseconds and the minimum TA-SURE
parameter is T-LPX nanoseconds. Likewise, the kernel doc of the 'lpx' and
'ta_sure' members of struct phy_configure_opts_mipi_dphy mentions that
the minimum values are 50000 picoseconds and @lpx picoseconds respectively.
Also, the function phy_mipi_dphy_config_validate() checks if cfg->lpx is
less than 50000 picoseconds and if cfg->ta_sure is less than cfg->lpx,
which hints the same minimum values.

Without this patch, the function phy_mipi_dphy_get_default_config()
wrongly sets cfg->lpx to 60000 picoseconds and cfg->ta_sure to 2 * cfg->lpx.
So, let's correct them to 50000 picoseconds and cfg->lpx respectively.

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.

Signed-off-by: Liu Ying <victor.liu@nxp.com>
Link: https://lore.kernel.org/r/20220216071257.1647703-1-victor.liu@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
---

drivers/phy/phy-core-mipi-dphy.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/phy-core-mipi-dphy.c b/drivers/phy/phy-core-mipi-dphy.c
index 727c2b040520..79cab9125002 100644
--- a/drivers/phy/phy-core-mipi-dphy.c
+++ b/drivers/phy/phy-core-mipi-dphy.c
@@ -64,10 +64,10 @@ static int phy_mipi_dphy_calc_config(unsigned long pixel_clock,
cfg->hs_trail = max(4 * 8 * ui, 60000 + 4 * 4 * ui);

cfg->init = 100;
- cfg->lpx = 60000;
+ cfg->lpx = 50000;
cfg->ta_get = 5 * cfg->lpx;
cfg->ta_go = 4 * cfg->lpx;
- cfg->ta_sure = 2 * cfg->lpx;
+ cfg->ta_sure = cfg->lpx;
cfg->wakeup = 1000;

cfg->hs_clk_rate = hs_clk_rate;
--
2.43.0