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rockchip64-current: HDMI resolutions (NanoPi M4v2)



I'm working on a project using the nanopim4v2-current image.  I noticed an issue with the available HDMI output resolutions.  Only a select few resolutions are available, despite the connected screen advertising support for additional ones.  I was also unable to output a custom resolution (for example 1920x538) by adding the proper modeline in manually through xrandr.


I've been looking into this for a bit and managed to find a partial solution in Miouyouyou's recent pull request "[RFC] RK3288 : Add HDMI resolutions".   Adding the patches to my build enabled support for my monitor's native resolution (1920x1200) and allowed me the ability to output custom resolutions as well.  However, some custom resolutions, which work with the legacy 4.4.x kernel, still don't output properly.


The restriction on the available resolutions stems from the dw_hdmi_rockchip_mode_valid function.  It currently rejects any modes with a clock rate that isn't in the rockchip_mpll_cfg table (as mentioned by Kwiboo).  I'm able to fix my issue by just removing the registration of the helper function with the following patch:

diff --git a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
index 906891b03..8a9ccf508 100644
--- a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
@@ -459,7 +459,6 @@ static struct rockchip_hdmi_chip_data rk3399_chip_data = {
 static const struct dw_hdmi_plat_data rk3399_hdmi_drv_data = {
-       .mode_valid = dw_hdmi_rockchip_mode_valid,
        .mpll_cfg   = rockchip_mpll_cfg,
        .cur_ctr    = rockchip_cur_ctr,
        .phy_config = rockchip_phy_config,

I'd like to see this functionality (setting custom resolutions) added to Armbian.   Is this a patch worth submitting as a pull request?  I understand that this is more of a hack than a proper solution.   I saw that Kwiboo mentioned he was working on something more comprehensive.


What can I do to help with this?

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