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Mon, 24 Aug 2020 07:44:56 +0000 (GMT) Subject: Re: [PATCH] memory: samsung: exynos5422-dmc: propagate error from exynos5_counters_get() To: Lukasz Luba , Krzysztof Kozlowski Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Bartlomiej Zolnierkiewicz , linux-samsung-soc@vger.kernel.org, Chanwoo Choi From: Marek Szyprowski Message-ID: Date: Mon, 24 Aug 2020 09:44:56 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: Content-Transfer-Encoding: 8bit Content-Language: en-US X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrMKsWRmVeSWpSXmKPExsWy7djP87o/853jDe4fEbHYOGM9q8X1L89Z Lc6f38BucXnXHDaLz71HGC1mnN/HZLGwqYXdgd1jzbw1jB6bVnWyefRtWcXo8XmTXABLFJdN SmpOZllqkb5dAlfGm81rWQruyVbs3vabrYHxgUQXIweHhICJxNwW3i5GLg4hgRWMEk9bPzJD OF8YJd4eWAjlfGaUaDvwnb2LkROsY+KmN2wQieWMEks+XGMCSQgJvGeUmLFfEMQWFkiW2DHz OyPIChEBH4klr9VBwswCexklVh4LA7HZBAwlut52sYHYvAJ2EmcunWQHKWcRUJWYsDUNJCwq ECex9fhVJogSQYmTM5+wgNicAtYSnVc/s0OMlJdo3jqbGcIWl7j1ZD4TyGkSAuvYJVZfuswM cbOLxP2fs1ghbGGJV8e3QP0iI3F6cg8LREMzo8TDc2vZIZweRonLTTMYIaqsJe6c+8UGch2z gKbE+l36EGFHif5DP5ghwcgnceOtIMQRfBKTtk2HCvNKdLQJQVSrScw6vg5u7cELl5gnMCrN QvLaLCTvzELyziyEvQsYWVYxiqeWFuempxYb5aWW6xUn5haX5qXrJefnbmIEJp3T/45/2cG4 60/SIUYBDkYlHt4fh+zjhVgTy4orcw8xSnAwK4nwOp09HSfEm5JYWZValB9fVJqTWnyIUZqD RUmc13jRy1ghgfTEktTs1NSC1CKYLBMHp1QDo5ZT/ZWock7pqWsuF0emJXCpuH+vW/euk1X2 a11Fd62UtpnRjzPl4oY7/4S/+Pr5v6D1d1F9j8UBOxj8avRFMzzeXtF+neeqNzmhfdfBFx2s T4OuuZ697+JsFht67Xrzn1bW120V4UynVlXPkFFd3ca6Wu/4ncQZev12lol/tdr2WFhpPV+g xFKckWioxVxUnAgAhn3NIzYDAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrBIsWRmVeSWpSXmKPExsVy+t/xu7o/8p3jDWZ9M7fYOGM9q8X1L89Z Lc6f38BucXnXHDaLz71HGC1mnN/HZLGwqYXdgd1jzbw1jB6bVnWyefRtWcXo8XmTXABLlJ5N UX5pSapCRn5xia1StKGFkZ6hpYWekYmlnqGxeayVkamSvp1NSmpOZllqkb5dgl7Gm81rWQru yVbs3vabrYHxgUQXIyeHhICJxMRNb9i6GLk4hASWMkr0fWpjgUjISJyc1sAKYQtL/LnWBVX0 llFiV8dEJpCEsECyxI6Z3xm7GDk4RAR8JJa8VgepYRbYyyjxZPpPJoiGP0wSk5/eB5vKJmAo 0fUWZBInB6+AncSZSyfZQZpZBFQlJmxNAwmLCsRJPO79zwxRIihxcuYTsFZOAWuJzquf2UFs ZgEziXmbHzJD2PISzVtnQ9niEreezGeawCg0C0n7LCQts5C0zELSsoCRZRWjSGppcW56brGR XnFibnFpXrpecn7uJkZgrG079nPLDsaud8GHGAU4GJV4eH8cso8XYk0sK67MPcQowcGsJMLr dPZ0nBBvSmJlVWpRfnxRaU5q8SFGU6DfJjJLiSbnA9NAXkm8oamhuYWlobmxubGZhZI4b4fA wRghgfTEktTs1NSC1CKYPiYOTqkGRgWZGdEN7sIhPVGmj6uUFurl3vC9KGDxyPBiy7n7/Xnq X+a8+RnGpv7n5AoJgVdJQu1XXp+xfVR6Pbnh508e4ZV/p355XLIgvOoIn4HPJ+fzRauf/bkW oZ8g//aYqO7biJsXhE3DF066JRNo+3WX8+VMzXlavJ7eBywjTxqkr65vurtqrmGIhhJLcUai oRZzUXEiAG+UG9jLAgAA X-CMS-MailID: 20200824074456eucas1p1b3b686114ef31dd5ba8bd1e87d923894 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20200804061225eucas1p283c1e0dc404bc420a2184480fdfd2b0d X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20200804061225eucas1p283c1e0dc404bc420a2184480fdfd2b0d References: <20200804061210.5415-1-m.szyprowski@samsung.com> <24675559-b807-5b80-1318-805c1530ffb3@arm.com> <78c95f58-8142-7607-6d74-5cfa6a7ffb77@samsung.com> <20200817120724.GC2346@kozik-lap> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 17.08.2020 14:27, Lukasz Luba wrote: > On 8/17/20 1:07 PM, Krzysztof Kozlowski wrote: >> On Tue, Aug 04, 2020 at 01:38:11PM +0100, Lukasz Luba wrote: >>> On 8/4/20 1:19 PM, Marek Szyprowski wrote: >>>> On 04.08.2020 11:11, Lukasz Luba wrote: >>>>> On 8/4/20 7:12 AM, Marek Szyprowski wrote: >>>>>> exynos5_counters_get() might fail with -EPROBE_DEFER if the >>>>>> driver for >>>>>> devfreq event counter is not yet probed. Propagate that error >>>>>> value to >>>>>> the caller to ensure that the exynos5422-dmc driver will be >>>>>> probed again >>>>>> when devfreq event contuner is available. >>>>>> >>>>>> This fixes boot hang if both exynos5422-dmc and exynos-ppmu >>>>>> drivers are >>>>>> compiled as modules. >>>>>> >>>>>> Signed-off-by: Marek Szyprowski >>>>>> --- >>>>>>     drivers/memory/samsung/exynos5422-dmc.c | 2 +- >>>>>>     1 file changed, 1 insertion(+), 1 deletion(-) >>>>>> >>>>>> diff --git a/drivers/memory/samsung/exynos5422-dmc.c >>>>>> b/drivers/memory/samsung/exynos5422-dmc.c >>>>>> index b9c7956e5031..639811a3eecb 100644 >>>>>> --- a/drivers/memory/samsung/exynos5422-dmc.c >>>>>> +++ b/drivers/memory/samsung/exynos5422-dmc.c >>>>>> @@ -914,7 +914,7 @@ static int exynos5_dmc_get_status(struct device >>>>>> *dev, >>>>>>         } else { >>>>>>             ret = exynos5_counters_get(dmc, &load, &total); >>>>>>             if (ret < 0) >>>>>> -            return -EINVAL; >>>>>> +            return ret; >>>>>>               /* To protect from overflow, divide by 1024 */ >>>>>>             stat->busy_time = load >> 10; >>>>>> >>>>> >>>>> Thank you for the patch, LGTM. >>>>> Some questions are still there, though. The function >>>>> exynos5_performance_counters_init() should capture that the counters >>>>> couldn't be enabled or set. So the functions: >>>>> exynos5_counters_enable_edev() and exynos5_counters_set_event() >>>>> must pass gently because devfreq device is registered. >>>>> Then devfreq checks device status, and reaches the state when >>>>> counters 'get' function returns that they are not ready... >>>>> >>>>> If that is a kind of 2-stage initialization, maybe we should add >>>>> another 'check' in the exynos5_performance_counters_init() and call >>>>> the devfreq_event_get_event() to make sure that we are ready to go, >>>>> otherwise return ret from that function (which is probably >>>>> EPROBE_DEFER) >>>>> and not register the devfreq device. >>>> >>>> I've finally investigated this further and it turned out that the >>>> issue >>>> is elsewhere. The $subject patch can be discarded, as it doesn't fix >>>> anything. The -EPROBE_DEFER is properly returned by >>>> exynos5_performance_counters_init(), which redirects >>>> exynos5_dmc_probe() >>>> to remove_clocks label. This causes disabling mout_bpll/fout_bpll >>>> clocks >>>> what in turn *sometimes* causes boot hang. This random behavior >>>> mislead >>>> me that the $subject patch fixes the issue, but then longer tests >>>> revealed that it didn't change anything. >>> >>> Really good investigation, great work Marek! >>> >>>> >>>> It looks that the proper fix would be to keep fout_bpll enabled all >>>> the >>>> time. >>> >>> Yes, I agree. I am looking for your next patch to test it then. >> >> Hi all, >> >> Is the patch still useful then? Shall I apply it? > > Marek has created different patch for it, which fixes the clock: > https://lore.kernel.org/linux-clk/20200807133143.22748-1-m.szyprowski@samsung.com/ > > > So you don't have to apply this one IMO. Indeed, you can drop this one. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland