From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0B2821349 for ; Tue, 3 Oct 2023 16:05:03 +0000 (UTC) Received: from mo4-p01-ob.smtp.rzone.de (mo4-p01-ob.smtp.rzone.de [81.169.146.167]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 219BAAF; Tue, 3 Oct 2023 09:04:59 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1696349096; cv=none; d=strato.com; s=strato-dkim-0002; b=S6ff578BowUfZj+1y4YbL9FMxYk8NpzCFUvB9oK9VrY2LRwfWN0H+JiPRjJ4vqUlka iOmqvtuPsen7sk+XYwr+qRrEK2qO0l7P712+nsYuVzR7fiDxZCAMLyLhIu/11WRyYo9s Ps7BjssuNp42/9q/Wv9cGcu+MIWphYnXuNxHurj45fet0hZeVhiUhErq5EzilPy9//Nl So4N4V6aa4NdHvMZwCShnFVTDNhKehKfWNJPHan2Vw5IKQQnl6+ccR10bHhzo0GZnl5E mAd1mJDd9uQZ3ePUrH32fQySnR5IaEAXpRhh5aqLwJuUvm+GWVuXygbesURm5V59Pqg6 UZZg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; t=1696349096; s=strato-dkim-0002; d=strato.com; h=In-Reply-To:References:Message-ID:Subject:Cc:To:From:Date:Cc:Date: From:Subject:Sender; bh=Fm0HbIGZeonJjTsTuZTF1RqPernihQA9D5wXeryyyjA=; b=ZEqlEC1vDYbAaheXC+lj6aM7qPqno1r2AZn5vE2nlYCv9mASeoYbkPf4bIyjPGFI7x ey8Lgr8kOcPyvcZupFZav0u37x9EVT7+H+n63tSQP+9/UG6lVYcRoxRW04YszF3o+h7x edD5Am0apPhkqbPYuIt3nkRHH6oAOURZiHVTOH7f8XSYZZ3K/I1VJQTyf01vYX48OKGR +0oGvFTQQunvcwjwo+exgfl7asj2UyYE+LJkICZ2L/VnPZE+gJ7WQJgpQC1MfRMqaZCD 8U6cF9og/J6rzqVzZ1zmzKT5NKWl+VHeayQIj869iSlXcqflGQBF+Y0bTJQmbBSRNzNf bfRQ== ARC-Authentication-Results: i=1; strato.com; arc=none; dkim=none X-RZG-CLASS-ID: mo01 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; t=1696349096; s=strato-dkim-0002; d=gerhold.net; h=In-Reply-To:References:Message-ID:Subject:Cc:To:From:Date:Cc:Date: From:Subject:Sender; bh=Fm0HbIGZeonJjTsTuZTF1RqPernihQA9D5wXeryyyjA=; b=eZOLwXZ/heVgjvqGk3RLwOtgM1AkmobM3dqBjEQlhLtdlAlNiiTNyNe73y9Ref9yO9 1AoIUwpyzXwbvxQWSnJqLNX7Sr9GLwXu9uimGBZqlXye2JTEMVk/7TpNYTDeNO7DPx9d rs3Yabvu5KmRWCStOeGxjxv3aXfsKc6xsGy7GyL5hOlotcMoDlHJrpLyttTCVEQf7+hc o8az18aPbKvoQ7JCTqwhWwF0AuB/ql3k2K+jM54GEHIsSvrF24I6evLlBW8LCil7BDwo JpExuz/TekkdtIOuRg+5H9ylqP6YqOqqnXz8e+wpA58hjQbxqoU2tV7S6+eu1F20r4L2 KkNw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; t=1696349096; s=strato-dkim-0003; d=gerhold.net; h=In-Reply-To:References:Message-ID:Subject:Cc:To:From:Date:Cc:Date: From:Subject:Sender; bh=Fm0HbIGZeonJjTsTuZTF1RqPernihQA9D5wXeryyyjA=; b=aWQH+0CSM5uZCY8uleo4ZcdHXJNeCnXKqTRK5jDTIy+zlCA9x+9eD0bQ0mbCAjCaBA 1XJUpSbKAwNAqjJ1UFDw== X-RZG-AUTH: ":P3gBZUipdd93FF5ZZvYFPugejmSTVR2nRPhVOQ/OcYgojyw4j34+u261EJF5OxJD4peA8paF1A==" Received: from gerhold.net by smtp.strato.de (RZmta 49.8.2 DYNA|AUTH) with ESMTPSA id R04c57z93G4t2dD (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits)) (Client did not present a certificate); Tue, 3 Oct 2023 18:04:55 +0200 (CEST) Date: Tue, 3 Oct 2023 18:04:48 +0200 From: Stephan Gerhold To: Dmitry Baryshkov Cc: Stephen Boyd , Andy Gross , Bjorn Andersson , Conor Dooley , Georgi Djakov , Ilia Lin , Konrad Dybcio , Krzysztof Kozlowski , Michael Turquette , Nishanth Menon , "Rafael J. Wysocki" , Rob Herring , Viresh Kumar , linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-pm@vger.kernel.org, linux-clk@vger.kernel.org, Christian Marangi Subject: Re: [PATCH v4 05/23] interconnect: icc-clk: add support for scaling using OPP Message-ID: References: <20230827115033.935089-1-dmitry.baryshkov@linaro.org> <20230827115033.935089-6-dmitry.baryshkov@linaro.org> <493aff10d698c9ca5bdbeae45250f5fe.sboyd@kernel.org> <7312633f-3b53-43a1-b6e3-010513c2a1e2@linaro.org> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_PASS,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Tue, Oct 03, 2023 at 06:31:27PM +0300, Dmitry Baryshkov wrote: > On Tue, 3 Oct 2023 at 17:17, Stephan Gerhold wrote: > > On Tue, Oct 03, 2023 at 04:36:11PM +0300, Dmitry Baryshkov wrote: > > > On Tue, 3 Oct 2023 at 16:02, Stephan Gerhold wrote: > > > > On Tue, Oct 03, 2023 at 11:30:28AM +0300, Dmitry Baryshkov wrote: > > > > > On 28/08/2023 21:09, Stephen Boyd wrote: > > > > > > Quoting Dmitry Baryshkov (2023-08-27 04:50:15) > > > > > > > diff --git a/drivers/interconnect/icc-clk.c b/drivers/interconnect/icc-clk.c > > > > > > > index d787f2ea36d9..45ffb068979d 100644 > > > > > > > --- a/drivers/interconnect/icc-clk.c > > > > > > > +++ b/drivers/interconnect/icc-clk.c > > > > > > > @@ -25,12 +28,16 @@ struct icc_clk_provider { > > > > > > > static int icc_clk_set(struct icc_node *src, struct icc_node *dst) > > > > > > > { > > > > > > > struct icc_clk_node *qn = src->data; > > > > > > > + unsigned long rate = icc_units_to_bps(src->peak_bw); > > > > > > > int ret; > > > > > > > if (!qn || !qn->clk) > > > > > > > return 0; > > > > > > > - if (!src->peak_bw) { > > > > > > > + if (qn->opp) > > > > > > > + return dev_pm_opp_set_rate(qn->dev, rate); > > > > > > > > > > > > Just curious how does lockdep do with this? Doesn't OPP call into > > > > > > interconnect code, so lockdep will complain about ABBA? > > > > > > > > > > Unfortunately it does. It seems, the icc-clk is not a proper way to go here. > > > > > I will take a look at reusing set_required_opps for this case. > > > > > > > > > > > > > Could you elaborate a bit which locks exactly cause trouble here? > > > > I'm probably missing something here. > > > > > > > > From a quick look at the OPP code I don't see a global lock taken there > > > > for the entire OPP switch sequence, so I'm not sure how this could cause > > > > an ABBA deadlock. > > > > > > For example: > > > > > > [ 7.680041] Chain exists of: > > > [ 7.680041] icc_bw_lock --> regulator_ww_class_acquire --> fs_reclaim > > > [ 7.680041] > > > [ 7.687955] Possible unsafe locking scenario: > > > [ 7.687955] > > > [ 7.699039] CPU0 CPU1 > > > [ 7.704752] ---- ---- > > > [ 7.709266] lock(fs_reclaim); > > > [ 7.713779] lock(regulator_ww_class_acquire); > > > [ 7.716919] lock(fs_reclaim); > > > [ 7.724204] lock(icc_bw_lock); > > > > > > > Hm, I'm not entirely sure how to interpret this. Is there really a > > connection between OPP and ICC here? It looks more like ICC <-> > > regulator and somehow related to memory allocations (the fs_reclaim). > > > > Was there more output around this? > > [ 7.362902] ====================================================== > [ 7.363447] WARNING: possible circular locking dependency detected > [ 7.369434] 6.6.0-rc3-next-20230929-08870-g49503b4b9f55 #129 Not tainted > [ 7.375604] ------------------------------------------------------ > [ 7.382453] swapper/0/1 is trying to acquire lock: > [ 7.388437] c143445c (icc_bw_lock){+.+.}-{3:3}, at: icc_init+0x0/0x104 > [ 7.393225] > [ 7.393225] but task is already holding lock: > [ 7.399730] c1397444 (fs_reclaim){+.+.}-{0:0}, at: icc_init+0x18/0x104 > [ 7.405547] > [ 7.405547] which lock already depends on the new lock. > [ 7.405547] > [ 7.412077] > [ 7.412077] the existing dependency chain (in reverse order) is: > [ 7.420310] > [ 7.420310] -> #2 (fs_reclaim){+.+.}-{0:0}: > [ 7.427767] fs_reclaim_acquire+0x60/0x94 > [ 7.433492] __kmem_cache_alloc_node+0x30/0x2b4 > [ 7.437742] __kmalloc_node_track_caller+0x48/0x244 > [ 7.442954] kstrdup+0x30/0x58 > [ 7.448325] create_regulator+0x70/0x2b8 > [ 7.451981] regulator_resolve_supply+0x3bc/0x7f4 > [ 7.456234] regulator_register+0x9b0/0xb50 > [ 7.461352] devm_regulator_register+0x50/0x8c > [ 7.466216] rpm_reg_probe+0xf4/0x1a0 > [ 7.471244] platform_probe+0x5c/0xb0 > [ 7.475157] really_probe+0xc8/0x2d8 > [ 7.479318] __driver_probe_device+0x88/0x1a0 > [ 7.483488] driver_probe_device+0x30/0x108 > [ 7.488262] __driver_attach_async_helper+0x4c/0xa0 > [ 7.493133] async_run_entry_fn+0x24/0xb0 > [ 7.498504] process_one_work+0x208/0x5e4 > [ 7.502844] worker_thread+0x1e0/0x4a4 > [ 7.507356] kthread+0x100/0x120 > [ 7.511874] ret_from_fork+0x14/0x28 > [ 7.515428] > [ 7.515428] -> #1 (regulator_ww_class_acquire){+.+.}-{0:0}: > [ 7.519528] lock_release+0x164/0x340 > [ 7.526713] __mutex_unlock_slowpath+0x3c/0x2fc > [ 7.530626] regulator_lock_dependent+0x1a4/0x298 > [ 7.535839] regulator_set_voltage+0x30/0xfc > [ 7.540866] krait_l2_set_one_supply+0x28/0x84 > [ 7.545729] krait_l2_config_regulators+0x90/0x1c4 > [ 7.550851] _set_opp+0xf0/0x438 > [ 7.556144] dev_pm_opp_set_rate+0x118/0x224 > [ 7.559703] icc_node_add+0xe8/0x15c > [ 7.564474] icc_clk_register+0x150/0x208 > [ 7.568556] krait_l2_probe+0x100/0x114 > [ 7.572988] platform_probe+0x5c/0xb0 > [ 7.577495] really_probe+0xc8/0x2d8 > [ 7.581487] __driver_probe_device+0x88/0x1a0 > [ 7.585658] driver_probe_device+0x30/0x108 > [ 7.590433] __device_attach_driver+0x94/0x10c > [ 7.595300] bus_for_each_drv+0x84/0xd8 > [ 7.600326] __device_attach+0xac/0x1a8 > [ 7.604580] bus_probe_device+0x8c/0x90 > [ 7.608919] device_add+0x5c8/0x7a4 > [ 7.613265] of_platform_device_create_pdata+0x90/0xbc > [ 7.617260] qcom_cpufreq_init+0xa8/0x130 > [ 7.622984] do_one_initcall+0x68/0x2d8 > [ 7.627235] kernel_init_freeable+0x1ac/0x208 > [ 7.631752] kernel_init+0x18/0x12c > [ 7.636441] ret_from_fork+0x14/0x28 > [ 7.640602] > [ 7.640602] -> #0 (icc_bw_lock){+.+.}-{3:3}: > [ 7.644607] __lock_acquire+0x1530/0x28fc > [ 7.650413] lock_acquire+0x10c/0x33c > [ 7.654757] icc_init+0x40/0x104 > [ 7.658917] do_one_initcall+0x68/0x2d8 > [ 7.662740] kernel_init_freeable+0x1ac/0x208 > [ 7.667168] kernel_init+0x18/0x12c > [ 7.671855] ret_from_fork+0x14/0x28 > [ 7.676018] > [ 7.676018] other info that might help us debug this: > [ 7.676018] > [ 7.680041] Chain exists of: > [ 7.680041] icc_bw_lock --> regulator_ww_class_acquire --> fs_reclaim > [ 7.680041] > [ 7.687955] Possible unsafe locking scenario: > [ 7.687955] > [ 7.699039] CPU0 CPU1 > [ 7.704752] ---- ---- > [ 7.709266] lock(fs_reclaim); > [ 7.713779] lock(regulator_ww_class_acquire); > [ 7.716919] lock(fs_reclaim); > [ 7.724204] lock(icc_bw_lock); > [ 7.729833] > [ 7.729833] *** DEADLOCK *** > [ 7.729833] > [ 7.733071] 1 lock held by swapper/0/1: > [ 7.738691] #0: c1397444 (fs_reclaim){+.+.}-{0:0}, at: icc_init+0x18/0x104 > [ 7.742528] > [ 7.742528] stack backtrace: > [ 7.749463] CPU: 3 PID: 1 Comm: swapper/0 Not tainted > 6.6.0-rc3-next-20230929-08870-g49503b4b9f55 #129 > [ 7.754010] Hardware name: Generic DT based system > [ 7.763183] unwind_backtrace from show_stack+0x10/0x14 > [ 7.767957] show_stack from dump_stack_lvl+0x60/0x90 > [ 7.773082] dump_stack_lvl from check_noncircular+0x174/0x18c > [ 7.778288] check_noncircular from __lock_acquire+0x1530/0x28fc > [ 7.784018] __lock_acquire from lock_acquire+0x10c/0x33c > [ 7.790178] lock_acquire from icc_init+0x40/0x104 > [ 7.795475] icc_init from do_one_initcall+0x68/0x2d8 > [ 7.800159] do_one_initcall from kernel_init_freeable+0x1ac/0x208 > [ 7.805286] kernel_init_freeable from kernel_init+0x18/0x12c > [ 7.811361] kernel_init from ret_from_fork+0x14/0x28 > [ 7.817177] Exception stack(0xf081dfb0 to 0xf081dff8) > Thanks! I assume you haven't noticed an actual deadlock (i.e. cpufreq not progressing) without lockdep? FWIW I'm not fully convinced that this deadlock can actually happen in practice for your particular limited use case (i.e. that it is not a false positive). > > In general, I would expect that adjusting a regulator from an > > interconnect driver should be made possible somehow. Just because the > > RPM firmware or similar typically handles this internally on Qualcomm > > platforms doesn't mean no one else will ever need to do this. If you > > have a higher bandwidth requests, need to increase the clock, which > > again depends on a higher voltage, then you need to be able to do the > > regulator_set_voltage() from the ICC driver somehow. > > This kind of dependency is handled by the consumer, not by the ICC > driver. Usually we explicitly put them to the opp tables, matching > rates and volage. > Right, but I'm talking about the voltage requirements of the aggregated bus clock. The rate for that is calculated from the different bandwidth requirements from all the consumers and not just a single one. From the kernel perspective, the interconnect driver is the consumer of that clock. On Qualcomm SMD RPM platforms the voltage adjustment for those is handled behind the scenes by the RPM firmware (no idea about RPMH and RPM-old). But one could easily think of a (non-Qualcomm) SoC without RPM, where the interconnect driver calculates a particular bus rate for multiple consumers and then needs to vote for a power domain or regulator to be able to generate that clock safely. > I think I'll still check the required-opps approach. It will require > manually aggregating the L2 rate requirements, but then we will be > safe from such kinds of interdependencies. And maybe then we can also > rewrite msm8996 to use required-opps too. > Sure, thanks! I think at the moment the required-opps implementation is somewhat entangled with power domains/genpd but perhaps it's easy enough to refactor that to be more general. Thanks, Stephan