Messages in this thread | | | Subject | Re: [PATCH 3/6] clk: qcom: gdsc: enable optional power domain support | From | Rajendra Nayak <> | Date | Mon, 5 Jul 2021 10:03:21 +0530 |
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On 7/3/2021 8:50 AM, Bjorn Andersson wrote: > On Fri 02 Jul 02:35 CDT 2021, Rajendra Nayak wrote: > >> >> >> On 7/2/2021 2:27 AM, Bjorn Andersson wrote: >>> On Thu 01 Jul 15:12 CDT 2021, Dmitry Baryshkov wrote: >>> >>>> On Thu, 1 Jul 2021 at 07:23, Bjorn Andersson <bjorn.andersson@linaro.org> wrote: >>>>> >>>>> On Wed 30 Jun 15:29 CDT 2021, Dmitry Baryshkov wrote: >>>>> >>>>>> On Wed, 30 Jun 2021 at 20:11, Bjorn Andersson >>>>>> <bjorn.andersson@linaro.org> wrote: >>>>>>> >>>>>>> On Wed 30 Jun 10:47 CDT 2021, Dmitry Baryshkov wrote: >>>>>>> >>>>>>>> Hi, >>>>>>>> >>>>>>>> On Wed, 30 Jun 2021 at 18:00, Bjorn Andersson >>>>>>>> <bjorn.andersson@linaro.org> wrote: >>>>>>>>> >>>>>>>>> On Wed 30 Jun 08:31 CDT 2021, Dmitry Baryshkov wrote: >>>>>>>>> >>>>>>>>>> On sm8250 dispcc and videocc registers are powered up by the MMCX power >>>>>>>>>> domain. Currently we used a regulator to enable this domain on demand, >>>>>>>>>> however this has some consequences, as genpd code is not reentrant. >>>>>>>>>> >>>>>>>>>> Teach Qualcomm clock controller code about setting up power domains and >>>>>>>>>> using them for gdsc control. >>>>>>>>>> >>>>>>>>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> >>>>>>>>> >>>>>>>>> There's a proposal to add a generic binding for statically assigning a >>>>>>>>> performance states here: >>>>>>>>> >>>>>>>>> https://lore.kernel.org/linux-arm-msm/1622095949-2014-1-git-send-email-rnayak@codeaurora.org/ >>>>>> >>>>>> I checked this thread. It looks like Rajendra will also switch to the >>>>>> "required-opps" property. So if that series goes in first, we can drop >>>>>> the call to set_performance_state. If this one goes in first, we can >>>>>> drop the set_performance_state call after getting Rajendra's work in. >>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> But that said, do you really need this? >>>>>>>>> >>>>>>>>> The requirement for driving MMCX to LOW_SVS on SM8250 (and NOM on >>>>>>>>> SM8150/SC8180x) seems to only come from the fact that you push MDP_CLK >>>>>>>>> to 460MHz in &mdss. >>>>>>>>> >>>>>>>>> But then in &mdss_mdp you do the same using an opp-table based on the >>>>>>>>> actual MDP_CLK, which per its power-domains will scale MMCX accordingly. >>>>>>>> >>>>>>>> MDSS and DSI would bump up MMCX performance state requirements on >>>>>>>> their own, depending on the frequency being selected. >>>>>>>> >>>>>>> >>>>>>> Right, but as I copied things from the sm8250.dtsi to come up with >>>>>>> sm8150/sc8180x.dtsi I concluded that as soon as the assigned-clockrate >>>>>>> in &mdss kicks in I need the performance state to be at NOM. >>>>>>> >>>>>>> So keeping the assigned-clockrate in &mdss means that MMCX will never go >>>>>>> below NOM. >>>>>> >>>>>> No, because once MDP is fully running, it will lower the clock frequency: >>>>>> >>>>>> # grep mdp_clk /sys/kernel/debug/clk/clk_summary >>>>>> disp_cc_mdss_mdp_clk_src 1 1 0 >>>>>> 150000000 0 0 50000 ? >>>>>> disp_cc_mdss_mdp_clk 2 2 0 >>>>>> 150000000 0 0 50000 Y >>>>>> >>>>> >>>>> But won't that just lower the performance state requested by the >>>>> &mdss_mdp, while the &mdss still votes for NOM - with the outcome being >>>>> that we maintain NOM even if the clock goes down? >>>> >>>> &mdss doesn't vote on performance state. At least it does not on >>>> msm/msm-next which I have at hand right now. >>>> &mdss toggles mdss_gdsc, but does not assign any performance state. >>>> >>> >>> Right, but per the upstream implementation, enabling MDSS_GDSC could in >>> itself fail, because unless something else has driven up the performance >>> state the enable that trickles up won't actually turn on the supply. >>> >>>> On the other hand &mdss_mdp and &dsi0 clearly vote on mmcx's performance state. >>>> >>> >>> Right, but it does so as part of its clock scaling, so this makes >>> perfect sense to me. >>> >>>>> >>>>>>> >>>>>>>>> So wouldn't it be sufficient to ensure that MDSS_GDSC is parented by >>>>>>>>> MMCX and then use opp-tables associated with the devices that scales the >>>>>>>>> clock and thereby actually carries the "required-opps". >>>>>>>> >>>>>>>> Actually no. I set the performance state in the qcom_cc_map, so that >>>>>>>> further register access is possible. Initially I was doing this in the >>>>>>>> qcom_cc_really_probe() and it was already too late. >>>>>>>> Just to remind: this patchset is not about MDSS_GDSC being parented by >>>>>>>> MMCX, it is about dispcc/videocc registers being gated with MMCX. >>>>>>>> >>>>>>> >>>>>>> So you're saying that just enabling MMCX isn't enough to touch the >>>>>>> dispcc/videocc registers? If that's the case it seems like MMCX's >>>>>>> definition of "on" needs to be adjusted - because just specifying MMCX >>>>>>> as the power-domain for dispcc/videocc and enabling pm_runtime should >>>>>>> ensure that MMCX is enabled when the clock registers are accessed (I >>>>>>> don't see anything like that for the GDSC part though). >>>>>> >>>>>> No, it is not enough. If I comment out the set_performance_state call, >>>>>> the board reboots. >>>>>> >>>>>> However I can set the opps as low as RET and register access will work. >>>>>> I'll run more experiments and if everything works as expected, I can >>>>>> use retention or min_svs level in the next iteration. >>>>>> Just note that downstream specifies low_svs as minimum voltage level >>>>>> for MMCX regulator. >>>>>> >>>>> >>>>> It doesn't make sense to me that a lone power_on on the power-domain >>>>> wouldn't give us enough juice to poke the registers. >>>>> >>>>> But digging into the rpmhpd implementation answers the question, simply >>>>> invoking rpmhpd_power_on() is a nop, unless >>>>> rpmhpd_set_performance_state() has previously been called, because >>>>> pd->corner is 0. So this explains why enable isn't sufficient. >>>>> >>>>> Compare this with the rpmpd implementation that will send an >>>>> enable request to the RPM in this case. >> >> Right, in case of RPMh, there was no separate 'enable' request which >> could be sent, there was just a 'corner' request. >> >> I don't completely recall, but the reason to not send a 'default corner' >> on enable was perhaps to keep the enable and set_performance orthogonal. >> >> However, given we then decided to send the lowest possible corner >> in disable, it perhaps makes sense to send a 'lowest non-zero corner' on enable >> as well. >> > > I was slightly worries that the change would dump cx and mx from > whatever level the bootloader put it at down to LOW_SVS during boot. > > But both rb3 and rb5 boots fine with this change, so I posted it here:
That seems to be a valid concern, perhaps this needs a little more wider testing on more platforms to really make sure it isn;t causing some regression.
> https://lore.kernel.org/linux-arm-msm/20210703025449.2687201-1-bjorn.andersson@linaro.org/ > >>>> >>>> Do you think that we should change that to: >>>> >>>> rpmhpd_aggregate_corner(pd, max(pd->corner, 1)) ? >>>> >>>> Or >>>> >>>> rpmhpd_aggregate_corner(pd, max(pd->corner, pd->levels[1])) ? >>>> >>> >>> In rpmhpd_power_on() and rpmhpd_set_performance_state() we pass the >>> index of the entry in pd->levels[] that we want, but in >>> rpmhpd_power_off() we pass the value of pd->levels[0]. >>> >>> So I would suggest dropping the if (pd->corner) and doing: >>> >>> rpmhpd_aggregate_corner(pd, max(pd->corner, 1)); >> >> So the index value represents the hlvl (0-15) that eventually gets sent to >> rpmh, the pd->levels are the sparse vlvl values that come from the command >> DB mappings. >> >> What seems sane is to sent the lowest non-zero vlvl. That in most cases >> would be at index 1, but for some which do not support complete off, >> it could be at index 0. >> > > I took this into consideration in above patch, keeping track of the > first non-zero corner and using this when the domain is enabled. > > Unfortunately, if the first entry would be say LOW_SVS power_off would > request corner (hlvl) 64. So I fixed that in patch 1/2 in above series.
That was by design to make sure rpmh does not ignore your request to 'turn off' a resource (since it really does not allow clients to dictate when to turn off) and keep it at the same level as before.
> > Regards, > Bjorn > >>> >>> And it seems both rb3 and rb5 still boots with this change (but I need >>> to do some more testing to know for sure). >>> >>>>> >>>>>>> I thought our problem you had was that you need to set a >>>>>>> performance_state in order to clock up some of the clocks - e.g. >>>>>>> MDP_CLK. >>>>>> >>>>>> No, even register access needs proper perf state. >>>>>> >>>>> >>>>> Per above finding you're right, enabling a rpmhpd power-domain doesn't >>>>> do anything. And I don't find this intuitive or even in line with the >>>>> expectations of the api... >>>>> >>>>> >>>>> >>>>> A quick test booting rb3 and rb5 seems to indicate that it's possible to >>>>> initialize pd->corner to 1 (to ensure that enable at least gives us the >>>>> lowest level). >>>>> >>>>> set_performance_state(0) will however then result in voting for "off", >>>>> rather than the lowest enabled level. >>>> >>>> Well, set_performance_state(0) means that "the device wouldn't >>>> participate anymore to find the target performance state of the >>>> genpd". >>> >>> I agree. >>> >>>> Strictly speaking it does not specify whether it is ok to turn >>>> it off or not. (like the regulator with the voltage set to 0V). >>>> But I'd also like to hear a comment from Stephen here. >>>> >>> >>> Looking at other power-domains (e.g. gdsc and rpmpd) enabling the >>> power-domain means it is no longer off and if you need some specific >>> performance state you have to vote for that. >>> >>> So I'm also interested in hearing if there's any reasoning behind how >>> this was written. >>> >>> Regards, >>> Bjorn >>> >> >> -- >> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member >> of Code Aurora Forum, hosted by The Linux Foundation
-- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
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