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<3938092a-bbc7-b304-641d-31677539598d@nvidia.com> <932d4d50-120c-9191-6a9a-23bf9c96633b@nvidia.com> <0ee055ad-d397-32e5-60ee-d62c14c6f77b@gmail.com> <86fc07d5-ab2e-a52a-a570-b1dfff4c20fe@nvidia.com> <20190716083701.225f0fd9@dimatab> <21266e4f-16b1-4c87-067a-16c07c803b6e@nvidia.com> <20190716080610.GE12715@pdeschrijver-desktop.Nvidia.com> <72b5df8c-8acb-d0d0-ebcf-b406e8404973@nvidia.com> <2b701832-5548-7c83-7c17-05cc2f1470c8@nvidia.com> <76e341be-6f38-2bc1-048e-1aa6883f9b88@gmail.com> <0706576a-ce61-1cf3-bed1-05f54a1e2489@nvidia.com> <5b2945c5-fcb2-2ac0-2bf2-df869dc9c713@gmail.com> <27641e30-fdd1-e53a-206d-71e1f23343fd@gmail.com> <10c4b9a2-a857-d124-c22d-7fd71a473079@nvidia.com> From: Sowjanya Komatineni Message-ID: <0ee06d1a-310d-59f7-0aa6-b688b33447f5@nvidia.com> Date: Tue, 16 Jul 2019 14:35:44 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Content-Language: en-US DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1563312947; bh=TbH2Sg2RNKnHnNv+Rv8LAiRrZ+5qlm8tym2Z+em68No=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Transfer-Encoding: Content-Language; b=sPS3ZCw9ZW36xlabFWZcP8L6TfefysKXaizPB6uxMqp55Nk+E4Wn7DvnxKFooHJX1 FDbrk/u4Bpz/FbjVC4vOiYEeGipjRiUjF2RLovABxGwrleviWIIV1qGDmuOLdKjbvC AJkE97wzUikXteaT1ZaG3d6Ub53OUWUCj4F504eBaY+AZ7Fjbp7ANqgOQe6/86AYT9 vD7MfGQxeuosWV61QEhPrFlEr1TlBs9zVdRhB2wFSgZ0a6GWsncmLFQQQHkcz+w7Zg DSlm/a0aY4nfm2ahz1XI9VrDEUSuD53YqtVICPcGty7xbFxd+WuOjvNo5lXdRGPCcE xAoFea1rMDwXA== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/16/19 2:21 PM, Dmitry Osipenko wrote: > 17.07.2019 0:12, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> On 7/16/19 1:47 PM, Dmitry Osipenko wrote: >>> 16.07.2019 22:26, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>> On 7/16/19 11:43 AM, Dmitry Osipenko wrote: >>>>> 16.07.2019 21:30, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>>>> On 7/16/19 11:25 AM, Dmitry Osipenko wrote: >>>>>>> 16.07.2019 21:19, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1= =82: >>>>>>>> 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 =D0=BF=D0=B8=D1=88=D0=B5=D1= =82: >>>>>>>>>>> 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 CPUFre= q >>>>>>>>>>>>>> driver >>>>>>>>>>>>>> implicitly relies on DFLL driver to be probed first, which i= s >>>>>>>>>>>>>> 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/t= egra/dc.c#L2383 >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> [2] >>>>>>>>>> https://www.kernel.org/doc/html/latest/driver-api/device_link.ht= ml >>>>>>>>>> >>>>>>>>>> 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 DFL= L >>>>>>>>>>>> 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 t= he >>>>>>>>>>>> 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 wit= h >>>>>>>>>>>> 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 duri= ng >>>>>>>>> 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 i= n >>>>>>>>>>>> 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 mod= e. >>>>>>>>>> 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, simila= r >>>>>>> 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 enabl= e >>>>>> 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 DFL= L >>>>> on a reboot, but likely that there are other clock-related problems a= s >>>>> 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=20 Vmin voltage and PLLP max is 408Mhz.