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[78.11.189.27]) by smtp.googlemail.com with ESMTPSA id q15-20020a1709060e4f00b006cdf4535cf2sm9473886eji.67.2022.03.23.02.47.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Mar 2022 02:47:05 -0700 (PDT) Message-ID: Date: Wed, 23 Mar 2022 10:47:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 From: Krzysztof Kozlowski Subject: Re: [PATCH 2/4] power: supply: max17042_battery: use ModelCfg refresh on max17055 Content-Language: en-US To: Sebastian Krzyszkowiak , Hans de Goede , Marek Szyprowski , Sebastian Reichel , linux-pm@vger.kernel.org Cc: Purism Kernel Team , Rob Herring , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org References: <20220318001048.20922-1-sebastian.krzyszkowiak@puri.sm> <7080597.aeNJFYEL58@pliszka> <5d43031e-382d-b12c-bba2-0e630fbec1ad@kernel.org> <2957015.e9J7NaK4W3@pliszka> In-Reply-To: <2957015.e9J7NaK4W3@pliszka> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 20/03/2022 21:44, Sebastian Krzyszkowiak wrote: > On niedziela, 20 marca 2022 13:18:49 CET Krzysztof Kozlowski wrote: >> On 18/03/2022 20:58, Sebastian Krzyszkowiak wrote: >>> On piątek, 18 marca 2022 09:22:16 CET Krzysztof Kozlowski wrote: >>>> On 18/03/2022 01:10, Sebastian Krzyszkowiak wrote: >>>>> Unlike other models, max17055 doesn't require cell characterization >>>>> data and operates on smaller amount of input variables (DesignCap, >>>>> VEmpty, IChgTerm and ModelCfg). Input data can already be filled in >>>>> by max17042_override_por_values, however model refresh bit has to be >>>>> set after adjusting input variables in order to make them apply. >>>>> >>>>> Signed-off-by: Sebastian Krzyszkowiak >>>>> --- >>>>> >>>>> drivers/power/supply/max17042_battery.c | 73 +++++++++++++++---------- >>>>> include/linux/power/max17042_battery.h | 3 + >>>>> 2 files changed, 48 insertions(+), 28 deletions(-) >>>>> >>>>> diff --git a/drivers/power/supply/max17042_battery.c >>>>> b/drivers/power/supply/max17042_battery.c index >>>>> c019d6c52363..c39250349a1d 100644 >>>>> --- a/drivers/power/supply/max17042_battery.c >>>>> +++ b/drivers/power/supply/max17042_battery.c >>>>> @@ -806,6 +806,13 @@ static inline void >>>>> max17042_override_por_values(struct max17042_chip *chip)> >>>>> >>>>> (chip->chip_type == MAXIM_DEVICE_TYPE_MAX17055)) { >>>>> >>>>> max17042_override_por(map, MAX17047_V_empty, config- >>>> >>>> vempty); >>>> >>>>> } >>>>> >>>>> + >>>>> + if (chip->chip_type == MAXIM_DEVICE_TYPE_MAX17055) { >>>>> + max17042_override_por(map, MAX17055_ModelCfg, config- >>>> >>>> model_cfg); >>>> >>>>> + // VChg is 1 by default, so allow it to be set to 0 >>>> >>>> Consistent comment, so /* */ >>>> >>>> I actually do not understand fully the comment and the code. You write >>>> entire model_cfg to MAX17055_ModelCfg and then immediately do it again, >>>> but with smaller mask. Why? >>> >>> That's because VChg is 1 on POR, and max17042_override_por doesn't do >>> anything when value equals 0 - which means that if the whole >>> config->model_cfg is 0, VChg won't get unset (which is needed for 4.2V >>> batteries). >>> >>> This could actually be replaced with a single regmap_write. >> >> I got it now. But if config->model_cfg is 0, should VChg be unset? > > That's a good question. > > max17042_override_por doesn't override the register value when the given value > equals zero in order to not override POR defaults with unset platform data. > This way one can set only the registers that they want to change in `config` > and the rest are untouched. This, however, only works if we assume that zero > means "don't touch", which isn't the case for ModelCfg. > > On the Librem 5, we need to unset VChg bit because our battery is only being > charged up to 4.2V. Allowing to unset this bit only without having to touch > the rest of the register was the motivation behind the current version of this > patch, however, thinking about it now I can see that it fails to do that in > the opposite case - when the DT contains a simple-battery with maximum voltage > higher than 4.25V, VChg will be set in config->model_cfg causing the whole > register to be overwritten. This is actually nice description which could be put into a comment there. > > So, I see two possible solutions: > > 1) move VChg handling to a separate variable in struct max17042_config_data. > This way model_cfg can stay zero when there's no need to touch the rest of the > register. This minimizes changes over current code. > > 2) remove max17042_override_por_values in its current shape altogether and > make it only deal with the values that are actually being set by the driver > (and only extend it in the future as it gains more ability). Currently most of > this function is only usable with platform data - is there actually any user > of max17042 that would need to configure the gauge without DT in the mainline > kernel? My quick search didn't find any. Do we need or want to keep platform > data support at all? > > I'm leaning towards option 2, as it seems to me that currently this driver is > being cluttered quite a lot by what's essentially a dead code. Adding new > parameters to read from DT for POR initialization (which is necessary for > other models than MAX17055) should be rather easy, but trying to fit them into > current platform_data-oriented code may be not. I am in for removal of platform data. Best regards, Krzysztof