lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Tue, 16 Jul 2019 19:35:49 -0700 From: Sowjanya Komatineni <skomatineni@...dia.com> To: Dmitry Osipenko <digetx@...il.com>, Peter De Schrijver <pdeschrijver@...dia.com>, Joseph Lo <josephl@...dia.com> CC: <thierry.reding@...il.com>, <jonathanh@...dia.com>, <tglx@...utronix.de>, <jason@...edaemon.net>, <marc.zyngier@....com>, <linus.walleij@...aro.org>, <stefan@...er.ch>, <mark.rutland@....com>, <pgaikwad@...dia.com>, <sboyd@...nel.org>, <linux-clk@...r.kernel.org>, <linux-gpio@...r.kernel.org>, <jckuo@...dia.com>, <talho@...dia.com>, <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <mperttunen@...dia.com>, <spatra@...dia.com>, <robh+dt@...nel.org>, <devicetree@...r.kernel.org> Subject: Re: [PATCH V5 11/18] clk: tegra210: Add support for Tegra210 clocks On 7/16/19 7:18 PM, Sowjanya Komatineni wrote: > > On 7/16/19 3:06 PM, Sowjanya Komatineni wrote: >> >> On 7/16/19 3:00 PM, Dmitry Osipenko wrote: >>> 17.07.2019 0:35, Sowjanya Komatineni пишет: >>>> On 7/16/19 2:21 PM, Dmitry Osipenko wrote: >>>>> 17.07.2019 0:12, Sowjanya Komatineni пишет: >>>>>> On 7/16/19 1:47 PM, Dmitry Osipenko wrote: >>>>>>> 16.07.2019 22:26, Sowjanya Komatineni пишет: >>>>>>>> On 7/16/19 11:43 AM, Dmitry Osipenko wrote: >>>>>>>>> 16.07.2019 21:30, Sowjanya Komatineni пишет: >>>>>>>>>> On 7/16/19 11:25 AM, Dmitry Osipenko wrote: >>>>>>>>>>> 16.07.2019 21:19, Sowjanya Komatineni пишет: >>>>>>>>>>>> On 7/16/19 9:50 AM, Sowjanya Komatineni wrote: >>>>>>>>>>>>> On 7/16/19 8:00 AM, Dmitry Osipenko wrote: >>>>>>>>>>>>>> 16.07.2019 11:06, Peter De Schrijver пишет: >>>>>>>>>>>>>>> On Tue, Jul 16, 2019 at 03:24:26PM +0800, Joseph Lo wrote: >>>>>>>>>>>>>>>>> OK, Will add to CPUFreq driver... >>>>>>>>>>>>>>>>>> The other thing that also need attention is that T124 >>>>>>>>>>>>>>>>>> CPUFreq >>>>>>>>>>>>>>>>>> driver >>>>>>>>>>>>>>>>>> implicitly relies on DFLL driver to be probed first, >>>>>>>>>>>>>>>>>> which is >>>>>>>>>>>>>>>>>> icky. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Should I add check for successful dfll clk register >>>>>>>>>>>>>>>>> explicitly in >>>>>>>>>>>>>>>>> CPUFreq driver probe and defer till dfll clk registers? >>>>>>>>>>>>>> Probably you should use the "device links". See [1][2] >>>>>>>>>>>>>> for the >>>>>>>>>>>>>> example. >>>>>>>>>>>>>> >>>>>>>>>>>>>> [1] >>>>>>>>>>>>>> https://elixir.bootlin.com/linux/v5.2.1/source/drivers/gpu/drm/tegra/dc.c#L2383 >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> [2] >>>>>>>>>>>>>> https://www.kernel.org/doc/html/latest/driver-api/device_link.html >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Return EPROBE_DEFER instead of EINVAL if device_link_add() >>>>>>>>>>>>>> fails. >>>>>>>>>>>>>> And >>>>>>>>>>>>>> use of_find_device_by_node() to get the DFLL's device, >>>>>>>>>>>>>> see [3]. >>>>>>>>>>>>>> >>>>>>>>>>>>>> [3] >>>>>>>>>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/devfreq/tegra20-devfreq.c#n100 >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>> Will go thru and add... >>>>>>>>>>> Looks like I initially confused this case with getting orphaned >>>>>>>>>>> clock. >>>>>>>>>>> I'm now seeing that the DFLL driver registers the clock and >>>>>>>>>>> then >>>>>>>>>>> clk_get(dfll) should be returning EPROBE_DEFER until DFLL >>>>>>>>>>> driver is >>>>>>>>>>> probed, hence everything should be fine as-is and there is >>>>>>>>>>> no real >>>>>>>>>>> need >>>>>>>>>>> for the 'device link'. Sorry for the confusion! >>>>>>>>>>> >>>>>>>>>>>>>>>> Sorry, I didn't follow the mail thread. Just regarding the >>>>>>>>>>>>>>>> DFLL >>>>>>>>>>>>>>>> part. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> As you know it, the DFLL clock is one of the CPU clock >>>>>>>>>>>>>>>> sources and >>>>>>>>>>>>>>>> integrated with DVFS control logic with the regulator. We >>>>>>>>>>>>>>>> will not >>>>>>>>>>>>>>>> switch >>>>>>>>>>>>>>>> CPU to other clock sources once we switched to DFLL. >>>>>>>>>>>>>>>> Because the >>>>>>>>>>>>>>>> CPU has >>>>>>>>>>>>>>>> been regulated by the DFLL HW with the DVFS table (CVB >>>>>>>>>>>>>>>> or OPP >>>>>>>>>>>>>>>> table >>>>>>>>>>>>>>>> you see >>>>>>>>>>>>>>>> in the driver.). We shouldn't reparent it to other sources >>>>>>>>>>>>>>>> with >>>>>>>>>>>>>>>> unknew >>>>>>>>>>>>>>>> freq/volt pair. That's not guaranteed to work. We allow >>>>>>>>>>>>>>>> switching to >>>>>>>>>>>>>>>> open-loop mode but different sources. >>>>>>>>>>>>>> Okay, then the CPUFreq driver will have to enforce DFLL >>>>>>>>>>>>>> freq to >>>>>>>>>>>>>> PLLP's >>>>>>>>>>>>>> rate before switching to PLLP in order to have a proper CPU >>>>>>>>>>>>>> voltage. >>>>>>>>>>>>> PLLP freq is safe to work for any CPU voltage. So no need to >>>>>>>>>>>>> enforce >>>>>>>>>>>>> DFLL freq to PLLP rate before changing CCLK_G source to PLLP >>>>>>>>>>>>> during >>>>>>>>>>>>> suspend >>>>>>>>>>>>> >>>>>>>>>>>> Sorry, please ignore my above comment. During suspend, need to >>>>>>>>>>>> change >>>>>>>>>>>> CCLK_G source to PLLP when dfll is in closed loop mode >>>>>>>>>>>> first and >>>>>>>>>>>> then >>>>>>>>>>>> dfll need to be set to open loop. >>>>>>>>>>> Okay. >>>>>>>>>>> >>>>>>>>>>>>>>>> And I don't exactly understand why we need to switch to >>>>>>>>>>>>>>>> PLLP in >>>>>>>>>>>>>>>> CPU >>>>>>>>>>>>>>>> idle >>>>>>>>>>>>>>>> driver. Just keep it on CL-DVFS mode all the time. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> In SC7 entry, the dfll suspend function moves it the >>>>>>>>>>>>>>>> open-loop >>>>>>>>>>>>>>>> mode. That's >>>>>>>>>>>>>>>> all. The sc7-entryfirmware will handle the rest of the >>>>>>>>>>>>>>>> sequence to >>>>>>>>>>>>>>>> turn off >>>>>>>>>>>>>>>> the CPU power. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> In SC7 resume, the warmboot code will handle the >>>>>>>>>>>>>>>> sequence to >>>>>>>>>>>>>>>> turn on >>>>>>>>>>>>>>>> regulator and power up the CPU cluster. And leave it on >>>>>>>>>>>>>>>> PLL_P. >>>>>>>>>>>>>>>> After >>>>>>>>>>>>>>>> resuming to the kernel, we re-init DFLL, restore the >>>>>>>>>>>>>>>> CPU clock >>>>>>>>>>>>>>>> policy (CPU >>>>>>>>>>>>>>>> runs on DFLL open-loop mode) and then moving to close-loop >>>>>>>>>>>>>>>> mode. >>>>>>>>>>>>>> The DFLL is re-inited after switching CCLK to DFLL parent >>>>>>>>>>>>>> during of >>>>>>>>>>>>>> the >>>>>>>>>>>>>> early clocks-state restoring by CaR driver. Hence instead of >>>>>>>>>>>>>> having >>>>>>>>>>>>>> odd >>>>>>>>>>>>>> hacks in the CaR driver, it is much nicer to have a proper >>>>>>>>>>>>>> suspend-resume sequencing of the device drivers. In this >>>>>>>>>>>>>> case >>>>>>>>>>>>>> CPUFreq >>>>>>>>>>>>>> driver is the driver that enables DFLL and switches CPU >>>>>>>>>>>>>> to that >>>>>>>>>>>>>> clock >>>>>>>>>>>>>> source, which means that this driver is also should be >>>>>>>>>>>>>> responsible for >>>>>>>>>>>>>> management of the DFLL's state during of suspend/resume >>>>>>>>>>>>>> process. If >>>>>>>>>>>>>> CPUFreq driver disables DFLL during suspend and >>>>>>>>>>>>>> re-enables it >>>>>>>>>>>>>> during >>>>>>>>>>>>>> resume, then looks like the CaR driver hacks around DFLL >>>>>>>>>>>>>> are not >>>>>>>>>>>>>> needed. >>>>>>>>>>>>>> >>>>>>>>>>>>>>>> The DFLL part looks good to me. BTW, change the patch >>>>>>>>>>>>>>>> subject to >>>>>>>>>>>>>>>> "Add >>>>>>>>>>>>>>>> suspend-resume support" seems more appropriate to me. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>> To clarify this, the sequences for DFLL use are as follows >>>>>>>>>>>>>>> (assuming >>>>>>>>>>>>>>> all >>>>>>>>>>>>>>> required DFLL hw configuration has been done) >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Switch to DFLL: >>>>>>>>>>>>>>> 0) Save current parent and frequency >>>>>>>>>>>>>>> 1) Program DFLL to open loop mode >>>>>>>>>>>>>>> 2) Enable DFLL >>>>>>>>>>>>>>> 3) Change cclk_g parent to DFLL >>>>>>>>>>>>>>> For OVR regulator: >>>>>>>>>>>>>>> 4) Change PWM output pin from tristate to output >>>>>>>>>>>>>>> 5) Enable DFLL PWM output >>>>>>>>>>>>>>> For I2C regulator: >>>>>>>>>>>>>>> 4) Enable DFLL I2C output >>>>>>>>>>>>>>> 6) Program DFLL to closed loop mode >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Switch away from DFLL: >>>>>>>>>>>>>>> 0) Change cclk_g parent to PLLP so the CPU frequency is >>>>>>>>>>>>>>> ok for >>>>>>>>>>>>>>> any >>>>>>>>>>>>>>> vdd_cpu voltage >>>>>>>>>>>>>>> 1) Program DFLL to open loop mode >>>>>>>>>>>>>>> >>>>>>>>>>>> I see during switch away from DFLL (suspend), cclk_g parent >>>>>>>>>>>> is not >>>>>>>>>>>> changed to PLLP before changing dfll to open loop mode. >>>>>>>>>>>> >>>>>>>>>>>> Will add this ... >>>>>>>>>>> The CPUFreq driver switches parent to PLLP during the probe, >>>>>>>>>>> similar >>>>>>>>>>> should be done on suspend. >>>>>>>>>>> >>>>>>>>>>> I'm also wondering if it's always safe to switch to PLLP in the >>>>>>>>>>> probe. >>>>>>>>>>> If CPU is running on a lower freq than PLLP, then some other >>>>>>>>>>> more >>>>>>>>>>> appropriate intermediate parent should be selected. >>>>>>>>>>> >>>>>>>>>> CPU parents are PLL_X, PLL_P, and dfll. PLL_X always runs at >>>>>>>>>> higher >>>>>>>>>> rate >>>>>>>>>> so switching to PLL_P during CPUFreq probe prior to dfll clock >>>>>>>>>> enable >>>>>>>>>> should be safe. >>>>>>>>> AFAIK, PLLX could run at ~200MHz. There is also a divided >>>>>>>>> output of >>>>>>>>> PLLP >>>>>>>>> which CCLKG supports, the PLLP_OUT4. >>>>>>>>> >>>>>>>>> Probably, realistically, CPU is always running off a fast PLLX >>>>>>>>> during >>>>>>>>> boot, but I'm wondering what may happen on KEXEC. I guess ideally >>>>>>>>> CPUFreq driver should also have a 'shutdown' callback to teardown >>>>>>>>> DFLL >>>>>>>>> on a reboot, but likely that there are other clock-related >>>>>>>>> problems as >>>>>>>>> well that may break KEXEC and thus it is not very important at >>>>>>>>> the >>>>>>>>> moment. >>>>>>>>> >>>>>>>>> [snip] >>>>>>>> During bootup CPUG sources from PLL_X. By PLL_P source above I >>>>>>>> meant >>>>>>>> PLL_P_OUT4. >>>>>>>> >>>>>>>> As per clock policies, PLL_X is always used for high freq like >>>>>>>> >800Mhz >>>>>>>> and for low frequency it will be sourced from PLLP. >>>>>>> Alright, then please don't forget to pre-initialize PLLP_OUT4 >>>>>>> rate to a >>>>>>> reasonable value using tegra_clk_init_table or assigned-clocks. >>>>>> PLLP_OUT4 rate update is not needed as it is safe to run at 408Mhz >>>>>> because it is below fmax @ Vmin >>>>> So even 204MHz CVB entries are having the same voltage as 408MHz, >>>>> correct? It's not instantly obvious to me from the DFLL driver's code >>>>> where the fmax @ Vmin is defined, I see that there is the >>>>> min_millivolts >>>>> and frequency entries starting from 204MHZ defined per-table. >>>> Yes at Vmin CPU Fmax is ~800Mhz. So anything below that will work at >>>> Vmin voltage and PLLP max is 408Mhz. >>> Thank you for the clarification. It would be good to have that >>> commented >>> in the code as well. >> OK, Will add... > > Regarding, adding suspend/resume to CPUFreq, CPUFreq suspend happens > very early even before disabling non-boot CPUs and also need to export > clock driver APIs to CPUFreq. > > Was thinking of below way of implementing this... > > > Clock DFLL driver Suspend: > > - Save CPU clock policy registers, and Perform dfll suspend > which sets in open loop mode > > CPU Freq driver Suspend: does nothing > > > Clock DFLL driver Resume: > > - Re-init DFLL, Set in Open-Loop mode, restore CPU Clock > policy registers which actually sets source to DFLL along with other > CPU Policy register restore. > > CPU Freq driver Resume: > > - do clk_prepare_enable which acutally sets DFLL in Closed > loop mode > > > Adding one more note: Switching CPU Clock to PLLP is not needed as CPU > CLock can be from dfll in open-loop mode as DFLL is not disabled > anywhere throught the suspend/resume path and SC7 entry FW and Warm > boot code will switch CPU source to PLLP.
Powered by blists - more mailing lists