• Liu Ying's avatar
    phy: dphy: Correct clk_pre parameter · 9a8406ba
    Liu Ying authored
    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: 2ed86999 ("phy: Add MIPI D-PHY configuration options")
    Tested-by: Liu Ying <victor.liu@nxp.com> # RM67191 DSI panel on i.MX8mq EVK
    Reviewed-by: default avatarAndrzej Hajda <andrzej.hajda@intel.com>
    Reviewed-by: Neil Armstrong <narmstrong@baylibre.com> # for phy-meson-axg-mipi-dphy.c
    Tested-by: Neil Armstrong <narmstrong@baylibre.com> # for phy-meson-axg-mipi-dphy.c
    Tested-by: Guido Günther <agx@sigxcpu.org> # Librem 5 (imx8mq) with it's rather picky panel
    Reviewed-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
    Signed-off-by: default avatarLiu Ying <victor.liu@nxp.com>
    Link: https://lore.kernel.org/r/20220124024007.1465018-1-victor.liu@nxp.comSigned-off-by: default avatarVinod Koul <vkoul@kernel.org>
    9a8406ba
phy-core-mipi-dphy.c 3.75 KB