On Wed, Mar 16, 2022 at 04:01:49PM +0300, Dmitry Osipenko wrote: > On 3/16/22 12:12, Sascha Hauer wrote: > > On Mon, Mar 14, 2022 at 08:54:27PM +0300, Dmitry Osipenko wrote: > >> On 3/14/22 11:18, Sascha Hauer wrote: > >>> On Sun, Mar 13, 2022 at 12:07:56AM +0300, Dmitry Osipenko wrote: > >>>> On 3/11/22 11:33, Sascha Hauer wrote: > >>>>> The rk3568 HDMI has an additional clock that needs to be enabled for the > >>>>> HDMI controller to work. This clock is not needed for the HDMI > >>>>> controller itself, but to make the SoC internal bus logic work. From the > >>>>> reference manual: > >>>>> > >>>>>> 2.8.6 NIU Clock gating reliance > >>>>>> > >>>>>> A part of niu clocks have a dependence on another niu clock in order to > >>>>>> sharing the internal bus. When these clocks are in use, another niu > >>>>>> clock must be opened, and cannot be gated. These clocks and the special > >>>>>> clock on which they are relied are as following: > >>>>>> > >>>>>> Clocks which have dependency The clock which can not be gated > >>>>>> ----------------------------------------------------------------- > >>>>>> ... > >>>>>> pclk_vo_niu, hclk_vo_s_niu hclk_vo_niu > >>>>>> ... > >>>>> The clock framework does not support turning on a clock whenever another > >>>>> clock is turned on, so this patch adds support for the dependent clock > >>>>> to the HDMI driver. We call it "NIU", which is for "Native Interface > >>>>> Unit" > >>>> > >>>> This still doesn't make sense to me. You're saying that "pclk_vo_niu, > >>>> hclk_vo_s_niu" depend on "hclk_vo_niu", but HDMI doesn't use pclk_vo, it > >>>> uses pclk_hdmi. > >>> > >>> pclk_hdmi_host is a child clock of pclk_vo: > >>> > >>> aclk_vo 2 2 0 300000000 0 0 50000 Y > >>> aclk_hdcp 0 0 0 300000000 0 0 50000 N > >>> pclk_vo 2 3 0 75000000 0 0 50000 Y > >>> pclk_edp_ctrl 0 0 0 75000000 0 0 50000 N > >>> pclk_dsitx_1 0 0 0 75000000 0 0 50000 N > >>> pclk_dsitx_0 1 2 0 75000000 0 0 50000 Y > >>> pclk_hdmi_host 1 2 0 75000000 0 0 50000 Y > >>> pclk_hdcp 0 0 0 75000000 0 0 50000 N > >>> hclk_vo 2 5 0 150000000 0 0 50000 Y > >>> hclk_hdcp 0 0 0 150000000 0 0 50000 N > >>> hclk_vop 0 2 0 150000000 0 0 50000 N > >> > >> It was unclear that the pclk_hdmi is the child of pclk_vo by looking at > >> the clk driver's code, thank you! > >> > >> Won't be better if the implicit clk dependency would be handled > >> internally by the RK clk driver? > > > > I have considered handling something like coupled clocks in the clock > > framework, but I have not yet considered handling this internally in the > > Rockchip clock driver. > > > > I just had a quick look at the driver. While it sounds like an easy task > > to enable gate A whenever gate B is enabled I haven't found a good way to > > integrate that into the clk driver. It seems to me that it's not easier > > to implement in the clk driver than it is to implement it in the clk > > framework where it could be used by others as well. > > > >> For example, by making the common gate > >> shared/refcounted. Have you considered this variant? Then we won't need > >> to change the DT bindings. > > > > For the DT bindings it is just an additional clock. Should we have a > > better way to handle that case in the future we could simply ignore the > > additional clock. I wouldn't bother too much about this. > > To me that NIU quirk should be internal to the clk h/w module, so it > doesn't feel nice to mix the clk h/w description with the HDMI h/w > description. > > On the other hand, making clk driver to handle this case indeed will > take some effort as I see now. For example, clk driver of NVIDIA Tegra > has concept of shared gates, but bringing it to the RK clk driver will > be quite messy. > > Alright, let's work around the clk limitation like you're suggesting. I > agree that it shouldn't really be a problem to deprecate the extra clock > later on. > > I have last questions.. > > 1. Previously you said that the PD driver takes care of enabling all the > clocks it can find in the device by itself on RPM-resume, then why HDMI > driver needs to enable the clock explicitly? The PD driver only does so when the device has pm_runtime enabled. Currently that's not the case for the hdmi driver. That could be changed of course, but I am not convinced that it's a good idea that the PD driver messes with the consumers clocks. It would also make the PD driver mandatory which it currently not is. > > 2. You added clk_prepare_enable(), but there is no corresponding > clk_disable_unprepare(), AFAICS. Why? Because I missed it ;) Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
