From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BC6C7C433FE for ; Wed, 12 Oct 2022 09:10:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229717AbiJLJKP (ORCPT ); Wed, 12 Oct 2022 05:10:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48856 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229727AbiJLJKK (ORCPT ); Wed, 12 Oct 2022 05:10:10 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 622E83343B; Wed, 12 Oct 2022 02:10:05 -0700 (PDT) Received: from [192.168.1.100] (2-237-20-237.ip236.fastwebnet.it [2.237.20.237]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: kholk11) by madras.collabora.co.uk (Postfix) with ESMTPSA id 0519B6601704; Wed, 12 Oct 2022 10:10:02 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1665565803; bh=QUqQMPPFvgEfJrocAzZzhDQ+j/eNqklToiqdvzIIEEQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=JgO98MGuvsNRNwEPVTmjJJ68GStUNy6gZtnPu6gvWu/fCuAXu6sCUFl4O+sUWz4bJ CZw/tkEO+liUlJnYnovpXEbsHKv8kjPfKaCBWnfFU9kFlM73//al/EVJOJk6ExcEmI Zm64tTmAqo29o+1JmnO6Wzag63JaztDffWJHKkwT2BKZEqty2CejO2ldu60qapgB/k uhzx2KXqfQQVJ7zyS9n5DVuirBihBlzW6ZniUCegKBQC95hSL9GgHW3qBcp19wRLSP dQCsqCBfEiUGevg0mL5Fsl4NMC1WnAtQgi5pUoHnryp8dqoxQqcZL7vXAXxolJqAn0 490jgHArm0uQA== Message-ID: Date: Wed, 12 Oct 2022 11:09:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [PATCH v2] clk: mediatek: clk-mux: Add .determine_rate() callback Content-Language: en-US To: Maxime Ripard Cc: sboyd@kernel.org, mturquette@baylibre.com, matthias.bgg@gmail.com, chun-jie.chen@mediatek.com, miles.chen@mediatek.com, wenst@chromium.org, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org References: <20221011135548.318323-1-angelogioacchino.delregno@collabora.com> <20221012085555.3nls7ja56vlnaz2w@houat> From: AngeloGioacchino Del Regno In-Reply-To: <20221012085555.3nls7ja56vlnaz2w@houat> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-clk@vger.kernel.org Il 12/10/22 10:55, Maxime Ripard ha scritto: > Hi, > > On Tue, Oct 11, 2022 at 03:55:48PM +0200, AngeloGioacchino Del Regno wrote: >> Since commit 262ca38f4b6e ("clk: Stop forwarding clk_rate_requests >> to the parent"), the clk_rate_request is .. as the title says, not >> forwarded anymore to the parent: > > It's not entirely true, the rate request should still be forwarded, but > we don't pass the same instance of clk_rate_request anymore. > >> this produces an issue with the MediaTek clock MUX driver during GPU >> DVFS on MT8195, but not on MT8192 or others. >> >> This is because, differently from others, like MT8192 where all of >> the clocks in the MFG parents tree are of mtk_mux type, but in the >> parent tree of MT8195's MFG clock, we have one mtk_mux clock and >> one (clk framework generic) mux clock, like so: >> >> names: mfg_bg3d -> mfg_ck_fast_ref -> top_mfg_core_tmp (or) mfgpll >> types: mtk_gate -> mux -> mtk_mux (or) mtk_pll >> >> To solve this issue and also keep the GPU DVFS clocks code working >> as expected, wire up a .determine_rate() callback for the mtk_mux >> ops; for that, the standard clk_mux_determine_rate_flags() was used >> as it was possible to. > > It probably fixes things indeed, but I'm a bit worried that it just > works around the actual issue instead of fixing the actual bug... > >> This commit was successfully tested on MT6795 Xperia M5, MT8173 Elm, >> MT8192 Spherion and MT8195 Tomato; no regressions were seen. >> >> For the sake of some more documentation about this issue here's the >> trace of it: >> >> [ 12.211587] ------------[ cut here ]------------ >> [ 12.211589] WARNING: CPU: 6 PID: 78 at drivers/clk/clk.c:1462 clk_core_init_rate_req+0x84/0x90 >> [ 12.211593] Modules linked in: stp crct10dif_ce mtk_adsp_common llc rfkill snd_sof_xtensa_dsp >> panfrost(+) sbs_battery cros_ec_lid_angle cros_ec_sensors snd_sof_of >> cros_ec_sensors_core hid_multitouch cros_usbpd_logger snd_sof gpu_sched >> snd_sof_utils fuse ipv6 >> [ 12.211614] CPU: 6 PID: 78 Comm: kworker/u16:2 Tainted: G W 6.0.0-next-20221011+ #58 >> [ 12.211616] Hardware name: Acer Tomato (rev2) board (DT) >> [ 12.211617] Workqueue: devfreq_wq devfreq_monitor >> [ 12.211620] pstate: 40400009 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) >> [ 12.211622] pc : clk_core_init_rate_req+0x84/0x90 >> [ 12.211625] lr : clk_core_forward_rate_req+0xa4/0xe4 >> [ 12.211627] sp : ffff80000893b8e0 >> [ 12.211628] x29: ffff80000893b8e0 x28: ffffdddf92f9b000 x27: ffff46a2c0e8bc05 >> [ 12.211632] x26: ffff46a2c1041200 x25: 0000000000000000 x24: 00000000173eed80 >> [ 12.211636] x23: ffff80000893b9c0 x22: ffff80000893b940 x21: 0000000000000000 >> [ 12.211641] x20: ffff46a2c1039f00 x19: ffff46a2c1039f00 x18: 0000000000000000 >> [ 12.211645] x17: 0000000000000038 x16: 000000000000d904 x15: 0000000000000003 >> [ 12.211649] x14: ffffdddf9357ce48 x13: ffffdddf935e71c8 x12: 000000000004803c >> [ 12.211653] x11: 00000000a867d7ad x10: 00000000a867d7ad x9 : ffffdddf90c28df4 >> [ 12.211657] x8 : ffffdddf9357a980 x7 : 0000000000000000 x6 : 0000000000000004 >> [ 12.211661] x5 : ffffffffffffffc8 x4 : 00000000173eed80 x3 : ffff80000893b940 >> [ 12.211665] x2 : 00000000173eed80 x1 : ffff80000893b940 x0 : 0000000000000000 >> [ 12.211669] Call trace: >> [ 12.211670] clk_core_init_rate_req+0x84/0x90 >> [ 12.211673] clk_core_round_rate_nolock+0xe8/0x10c >> [ 12.211675] clk_mux_determine_rate_flags+0x174/0x1f0 >> [ 12.211677] clk_mux_determine_rate+0x1c/0x30 >> [ 12.211680] clk_core_determine_round_nolock+0x74/0x130 >> [ 12.211682] clk_core_round_rate_nolock+0x58/0x10c >> [ 12.211684] clk_core_round_rate_nolock+0xf4/0x10c >> [ 12.211686] clk_core_set_rate_nolock+0x194/0x2ac >> [ 12.211688] clk_set_rate+0x40/0x94 >> [ 12.211691] _opp_config_clk_single+0x38/0xa0 >> [ 12.211693] _set_opp+0x1b0/0x500 >> [ 12.211695] dev_pm_opp_set_rate+0x120/0x290 >> [ 12.211697] panfrost_devfreq_target+0x3c/0x50 [panfrost] >> [ 12.211705] devfreq_set_target+0x8c/0x2d0 >> [ 12.211707] devfreq_update_target+0xcc/0xf4 >> [ 12.211708] devfreq_monitor+0x40/0x1d0 >> [ 12.211710] process_one_work+0x294/0x664 >> [ 12.211712] worker_thread+0x7c/0x45c >> [ 12.211713] kthread+0x104/0x110 >> [ 12.211716] ret_from_fork+0x10/0x20 >> [ 12.211718] irq event stamp: 7102 >> [ 12.211719] hardirqs last enabled at (7101): [] finish_task_switch.isra.0+0xec/0x2f0 >> [ 12.211723] hardirqs last disabled at (7102): [] el1_dbg+0x24/0x90 >> [ 12.211726] softirqs last enabled at (6716): [] __do_softirq+0x414/0x588 >> [ 12.211728] softirqs last disabled at (6507): [] ____do_softirq+0x18/0x24 >> [ 12.211730] ---[ end trace 0000000000000000 ]--- > > ... Indeed, you shouldn't hit that warning at all. It happens in > clk_core_round_rate_nolock, which takes (before your patch) the > CLK_SET_RATE_PARENT branch. This indeed has been changed by the patch > you mentioned, and will call clk_core_forward_rate_req() now, that in > turn calls clk_core_init_rate_nolock(). > > I think the warning you hit is because core->parent is NULL, which is > passed to clk_core_forward_rate_req() as the parent argument, and we'll > call clk_core_init_rate_req() with parent set as the core argument. > > In clk_core_init_rate_req(), the first thing we do is a WARN_ON(!core), > which is what you hit here I think. > > This is different to the previous behavior that was calling > clk_core_round_rate_nolock() with core->parent directly, and > clk_core_round_rate_nolock() if its core argument is NULL will set > req->rate to 0 and bail out without returning an error. > > Now, your patch probably works because now that you provide a > determine_rate implementation, clk_core_can_round() returns true and > you'll take a different branch in clk_core_round_rate_nolock(), avoiding > that issue entirely. > > Does that patch work better (on top of next-20221012)? Hello Maxime, I admit I didn't go too deep in the research, as my brain processed that as "this is a mux clock, not really different from a standard mux, this callback is missing, that's not optimal"... then that fixed it and called it a day. I should've prolonged my research for a better understanding of what was actually going on. What you said actually opened my mind and, with little surprise, your patch works as good as mine - no warnings and the clock scales as expected! I still think that the mtk-mux driver should get a determine_rate callback but, at this point, that's going to have an entirely different commit description... Please go on and send your patch: if you want, please remember to add me to the Cc's, so that I can give you my R-b tag in a timely manner. Cheers! Angelo > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index c3c3f8c07258..b831a4227236 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -1459,12 +1459,15 @@ static void clk_core_init_rate_req(struct clk_core * const core, > { > struct clk_core *parent; > > - if (WARN_ON(!core || !req)) > + if (WARN_ON(!req)) > return; > > memset(req, 0, sizeof(*req)); > - > req->rate = rate; > + > + if (!core) > + return; > + > clk_core_get_boundaries(core, &req->min_rate, &req->max_rate); > > parent = core->parent; > > Thanks! > Maxime