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    Subject[PATCH 5.12 342/677] drm/stm: Fix bus_flags handling
    Date
    From: Marek Vasut <marex@denx.de>

    [ Upstream commit 99e360442f223dd40fc23ae07c7a263836fd27e6 ]

    The drm_display_mode_to_videomode() does not populate DISPLAY_FLAGS_DE_LOW
    or DISPLAY_FLAGS_PIXDATA_NEGEDGE flags in struct videomode. Therefore, no
    matter what polarity the next bridge or display might require, these flags
    are never set, and thus the LTDC GCR_DEPOL and GCR_PCPOL bits are never set
    and the LTDC behaves as if both DISPLAY_FLAGS_PIXDATA_POSEDGE and
    DISPLAY_FLAGS_DE_HIGH were always set.

    The fix for this problem is taken almost verbatim from MXSFB driver. In
    case there is a bridge attached to the LTDC, the bridge might have extra
    polarity requirements, so extract bus_flags from the bridge and use them
    for LTDC configuration. Otherwise, extract bus_flags from the connector,
    which is the display.

    Fixes: b759012c5fa7 ("drm/stm: Add STM32 LTDC driver")
    Signed-off-by: Marek Vasut <marex@denx.de>
    Signed-off-by: Yannick Fertre <yannick.fertre@st.com>
    Cc: Alexandre Torgue <alexandre.torgue@st.com>
    Cc: Antonio Borneo <antonio.borneo@st.com>
    Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
    Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
    Cc: Philippe Cornu <philippe.cornu@st.com>
    Cc: Sam Ravnborg <sam@ravnborg.org>
    Cc: Vincent Abriou <vincent.abriou@st.com>
    Cc: Yannick Fertre <yannick.fertre@st.com>
    Cc: linux-arm-kernel@lists.infradead.org
    Cc: linux-stm32@st-md-mailman.stormreply.com
    To: dri-devel@lists.freedesktop.org
    Tested-by: Yannick Fertre <yannick.fertre@foss.st.com>
    Signed-off-by: Philippe Cornu <philippe.cornu@foss.st.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20210127110756.125570-1-marex@denx.de
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/gpu/drm/stm/ltdc.c | 33 +++++++++++++++++++++++++++++++--
    1 file changed, 31 insertions(+), 2 deletions(-)

    diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
    index 7812094f93d6..6f3b523e16e8 100644
    --- a/drivers/gpu/drm/stm/ltdc.c
    +++ b/drivers/gpu/drm/stm/ltdc.c
    @@ -525,13 +525,42 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
    {
    struct ltdc_device *ldev = crtc_to_ltdc(crtc);
    struct drm_device *ddev = crtc->dev;
    + struct drm_connector_list_iter iter;
    + struct drm_connector *connector = NULL;
    + struct drm_encoder *encoder = NULL;
    + struct drm_bridge *bridge = NULL;
    struct drm_display_mode *mode = &crtc->state->adjusted_mode;
    struct videomode vm;
    u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h;
    u32 total_width, total_height;
    + u32 bus_flags = 0;
    u32 val;
    int ret;

    + /* get encoder from crtc */
    + drm_for_each_encoder(encoder, ddev)
    + if (encoder->crtc == crtc)
    + break;
    +
    + if (encoder) {
    + /* get bridge from encoder */
    + list_for_each_entry(bridge, &encoder->bridge_chain, chain_node)
    + if (bridge->encoder == encoder)
    + break;
    +
    + /* Get the connector from encoder */
    + drm_connector_list_iter_begin(ddev, &iter);
    + drm_for_each_connector_iter(connector, &iter)
    + if (connector->encoder == encoder)
    + break;
    + drm_connector_list_iter_end(&iter);
    + }
    +
    + if (bridge && bridge->timings)
    + bus_flags = bridge->timings->input_bus_flags;
    + else if (connector)
    + bus_flags = connector->display_info.bus_flags;
    +
    if (!pm_runtime_active(ddev->dev)) {
    ret = pm_runtime_get_sync(ddev->dev);
    if (ret) {
    @@ -567,10 +596,10 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
    if (vm.flags & DISPLAY_FLAGS_VSYNC_HIGH)
    val |= GCR_VSPOL;

    - if (vm.flags & DISPLAY_FLAGS_DE_LOW)
    + if (bus_flags & DRM_BUS_FLAG_DE_LOW)
    val |= GCR_DEPOL;

    - if (vm.flags & DISPLAY_FLAGS_PIXDATA_NEGEDGE)
    + if (bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
    val |= GCR_PCPOL;

    reg_update_bits(ldev->regs, LTDC_GCR,
    --
    2.30.2


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