This patch series fixes a black screen seen at boot on Trogdor devices. The details of that problem are in the second patch, but the TL;DR is that shared RCGs report the wrong parent to the clk framework and shared RCGs never get turned off if they're left force enabled out of boot, wedging the display GDSC causing the display bridge to fail to probe because it can't turn on DSI. The first patch is basically a hack. It avoids a problem where the mdss driver probes, turns on and off the mdp clk, and hangs the rotator clk because the rotator clk is using the same parent. We don't care about this case on sc7180, so we simply disable the clk at driver probe so it can't get stuck on. The second patch fixes the shared RCG implementation so that the parent is properly reported and so that the force enable bit is cleared. Fixing the parent causes the problem that the first patch is avoiding, which is why that patch is first. Just applying this second patch will make it so that disabling the mdp clk disables the display pll that the rotator clk is also using, causing the rotator clk to be stuck on. This problem comes about because of a combination of issues. The clk framework doesn't handle the case where two clks share the same parent and are enabled at boot. The first clk to enable and disable will turn off the parent. The mdss driver doesn't stay out of runtime suspend while populating the child devices. In fact, of_platform_populate() triggers runtime resume and suspend of the mdss device multiple times while devices are being added. These patches side-step the larger issues here with the goal of fixing Trogdor in the short-term. Long-term we need to fix the clk framework and display driver so that shared parents aren't disabled during boot and so that mdss can't runtime suspend until the display pipeline/card is fully formed. Stephen Boyd (2): clk: qcom: dispcc-sc7180: Force off rotator clk at probe clk: qcom: Properly initialize shared RCGs upon registration drivers/clk/qcom/clk-rcg2.c | 19 +++++++++++++++++++ drivers/clk/qcom/dispcc-sc7180.c | 14 ++++++++++++++ 2 files changed, 33 insertions(+) Cc: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> Cc: Douglas Anderson <dianders@xxxxxxxxxxxx> Cc: Taniya Das <quic_tdas@xxxxxxxxxxx> Cc: Laura Nao <laura.nao@xxxxxxxxxxxxx> base-commit: e8f897f4afef0031fe618a8e94127a0934896aba -- https://chromeos.dev
