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Thu, 28 May 2020 13:11:43 +0000 (GMT) From: Marek Szyprowski To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Mark Brown , Dmitry Osipenko Cc: Marek Szyprowski , Liam Girdwood , Lucas Stach , Bartlomiej Zolnierkiewicz , Krzysztof Kozlowski , Viresh Kumar , peron.clem@gmail.com, Nishanth Menon , Stephen Boyd , Vincent Guittot , Rafael Wysocki , linux-samsung-soc@vger.kernel.org, Chanwoo Choi Subject: [PATCH] regulator: do not balance regulators without constraints Date: Thu, 28 May 2020 15:11:30 +0200 Message-Id: <20200528131130.17984-1-m.szyprowski@samsung.com> X-Mailer: git-send-email 2.17.1 X-Brightmail-Tracker: H4sIAAAAAAAAA0VSfSyUcRzv9zx3zz2ss8dh94smrrfV5H3tZ72MZuvp5Y/+qyUvh2eOvO3O y2lrIyNOpJZCwlhl5OXEdV5q0eW2xIm8lJfl1IwhIUJHzkP++7z+vt/v9iNxQRXXmgyNjGGk keJwEWHKUbUtdx7LVuv8nKdfuCJlbjUX5Yx+J1D/wjgXVfwaA0inq+Ghb0++YGjxcxqGehoL CDSfqQEoV/cGQ5WaYR6a+tOBocHCHg762N7NRWt9Sg5K0yziSPmb9jSnG/KHeXRteTpBD/U1 E/RdgzNd13ubQ2fVlQNaO/AKo+drbS+RV01PBjPhoXGM1Ol0gKmkLbsWi9YI5UsjedxEkGeh ACQJKXeo/ylRAFNSQJUBaNBouSxZAHAptx6wZB5AvUEPthtq3VlWfw5g/cLkTuNhi5pQABOS oFygYlpBGA1LKmkjVdyFGQ2cWsXh60/2RmxBnYOlc3O4EXOog3DdkL5Z5lOnYH7py00dUvtg Rc1b3PgQpFQ8+GAwjcca3vCDSr0VsoCT2rotfS9cbyjC2EIygKOdlTyW3AGw51YuYFMn4FDn CmE8CKeOwOpGJ1b2gqvpKVz2TjM4MG3OLm0G76se4azMh2mpAjZ9COZrq/6Pbenq3lqHhmOP yzhGLKB8YdHACpENbPN3ZhUDUA6ETKwsIoSRuUYy8Y4ycYQsNjLEMSgqohZs/KL2Ne2CGjT+ DWwFFAlEu/k1eTo/AVccJ0uIaAWQxEWW/DMd7X4CfrA44QYjjfKXxoYzslZgQ3JEQr5byYSv gAoRxzDXGSaakW67GGlinQiCo/fUFbu0Pi3omQg78O7ij6abU14iH3HzyFjJ+ytW9ql21ocv j2QWZnXJVVVfRcv6xnoHL+GujCkbf+Va1rVVb48ku7JxXfOslZvcw5B+PDn+3vnwC01hEgd5 X0WOfNAsqCrQpylAkjkgbPGcddc3hPU+W0qZqczonykhS+fj94s4MonY5SgulYn/ATXzBu5B AwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFmplkeLIzCtJLcpLzFFi42I5/e/4Pd0JO87HGXz4KmexccZ6VoupD5+w WVz/8pzVYvXHx4wW589vYLd4MPcmk8W3Kx1MFpd3zWGz+Nx7hNFixvl9TBZrj9xlt3jz4yyT xe15l1kszpy+xGrx79pGFouOI9+YLTZ+9XAQ9Ng56y67x6ZVnWwed67tYfPo/2vgseVqO4tH 35ZVjB7Hb2xn8vi8SS6AI0rPpii/tCRVISO/uMRWKdrQwkjP0NJCz8jEUs/Q2DzWyshUSd/O JiU1J7MstUjfLkEv49iETUwFR8Qrvt+bydrAOFO4i5GDQ0LARGLHefcuRi4OIYGljBJ3zmxj 7mLkBIrLSJyc1sAKYQtL/LnWxQZR9IlRYsmUJ+wgCTYBQ4mutxAJEYFWRonzr1cxgTjMAq0s EgvurAIbJSzgKbH40ycwm0VAVeL/3042EJtXwFZi1uLNUOvkJVZvOMA8gZFnASPDKkaR1NLi 3PTcYkO94sTc4tK8dL3k/NxNjMAo2Hbs5+YdjJc2Bh9iFOBgVOLh3TDzfJwQa2JZcWXuIUYJ DmYlEV6ns6fjhHhTEiurUovy44tKc1KLDzGaAi2fyCwlmpwPjNC8knhDU0NzC0tDc2NzYzML JXHeDoGDMUIC6YklqdmpqQWpRTB9TBycUg2MgnIT626c7mz5Kbmz96pa1ra/k9OORf1bZHnJ Xbxh0UPu2Pj9qnwWv7rk205sNp3GERa35BF3xa+ipt9pe5rrzt/MWf8zYe00pg13a124mtbH fbsmFh7tU3bnUkSasaNhz9niXWd0k+Z9Ctct/JL88upZY8bJU1jU7rGrRhRbKXm4bs7YfZlL iaU4I9FQi7moOBEAyCh4b5gCAAA= X-CMS-MailID: 20200528131144eucas1p121b9151996fa3f780a5028f68c69d5ba X-Msg-Generator: CA X-RootMTR: 20200528131144eucas1p121b9151996fa3f780a5028f68c69d5ba X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20200528131144eucas1p121b9151996fa3f780a5028f68c69d5ba References: Sender: linux-samsung-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org Balancing coupled regulators must wait until the clients for all of the coupled regualtors set their constraints, otherwise the balancing code might change the voltage of the not-yet-constrained regulator to the value below the bootloader-configured operation point, what might cause a system crash. Signed-off-by: Marek Szyprowski --- This is probably a generalization of the issue aleady observed and reported here: https://lore.kernel.org/linux-samsung-soc/20191008101709.qVNy8eijBi0LynOteWFMnTg4GUwKG599n6OyYoX1Abs@z/ https://lore.kernel.org/lkml/20191017102758.8104-1-m.szyprowski@samsung.com/ https://lore.kernel.org/linux-pm/cover.1589528491.git.viresh.kumar@linaro.org/ The problem is with "vdd_int" regulator coupled with "vdd_arm" on Odroid XU3/XU4 boards family. "vdd_arm" is handled by CPUfreq. "vdd_int" is handled by devfreq. CPUfreq initialized quite early during boot and it starts changing OPPs and "vdd_arm" value. Sometimes CPU activity during boot goes down and some low-frequency OPPs are selected, what in turn causes lowering "vdd_arm". This happens before devfreq applies its requirements on "vdd_int". Regulator balancing code reduces "vdd_arm" voltage value, what in turn causes lowering "vdd_int" value to the lowest possible value. This is much below the operation point of the wcore bus, which still runs at the highest frequency. The issue was hard to notice because in the most cases the board managed to boot properly, even when the regulator was set to lowest value allowed by the regulator constraints. However, it caused some random issues, which can be observed as "Unhandled prefetch abort" or low USB stability. I know that adding more and more special cases to the generic code is not the best idea, but so far I see no other way to fix this issue. The only other solution that comes to my mind is admiting that it is not possible to have generic regulator coupler and this needs board-specific code in all cases. Such code might take care of those corner cases if they are critical. Best regards, Marek Szyprowski --- drivers/regulator/core.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c index 941783a14b45..c1d77d44186b 100644 --- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -3697,10 +3697,21 @@ static int regulator_balance_voltage(struct regulator_dev *rdev, * the coupled voltages. */ int optimal_uV = 0, optimal_max_uV = 0, current_uV = 0; + int cons_uV = 0, cons_max_uV = INT_MAX; if (test_bit(i, &c_rdev_done)) continue; + ret = regulator_check_consumers(c_rdevs[i], + &cons_uV, + &cons_max_uV, state); + if (ret < 0) + goto out; + + /* no constraints set - ignore */ + if (cons_uV == 0) + continue; + ret = regulator_get_optimal_voltage(c_rdevs[i], ¤t_uV, &optimal_uV,