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([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-220d5366729sm105737245ad.79.2025.02.19.05.46.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Feb 2025 05:46:12 -0800 (PST) Sender: Guenter Roeck Message-ID: <07ec64e7-041d-4f5a-a04c-daa4b0794111@roeck-us.net> Date: Wed, 19 Feb 2025 05:46:10 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/2] hwmon: (amc6821) Add PWM polarity configuration with OF To: Quentin Schulz , Francesco Dolcini , Jean Delvare , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Farouk Bouabid Cc: Francesco Dolcini , linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250218165633.106867-1-francesco@dolcini.it> <20250218165633.106867-3-francesco@dolcini.it> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2/19/25 02:08, Quentin Schulz wrote: > Hi Francesco, > > On 2/18/25 5:56 PM, Francesco Dolcini wrote: >> From: Francesco Dolcini >> >> Add support to configure the PWM-Out pin polarity based on a device >> tree property. >> >> Signed-off-by: Francesco Dolcini >> --- >>   drivers/hwmon/amc6821.c | 7 +++++-- >>   1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c >> index 1e3c6acd8974..1ea2d97eebca 100644 >> --- a/drivers/hwmon/amc6821.c >> +++ b/drivers/hwmon/amc6821.c >> @@ -845,7 +845,7 @@ static int amc6821_detect(struct i2c_client *client, struct i2c_board_info *info >>       return 0; >>   } >> -static int amc6821_init_client(struct amc6821_data *data) >> +static int amc6821_init_client(struct i2c_client *client, struct amc6821_data *data) >>   { >>       struct regmap *regmap = data->regmap; >>       int err; >> @@ -864,6 +864,9 @@ static int amc6821_init_client(struct amc6821_data *data) >>           if (err) >>               return err; >> +        if (of_property_read_bool(client->dev.of_node, "ti,pwm-inverted")) > > I know that the AMC6821 is doing a lot of smart things, but this really tickled me. PWM controllers actually do support that already via PWM_POLARITY_INVERTED flag for example. See Documentation/devicetree/bindings/hwmon/adt7475.yaml which seems to be another HWMON driver which acts as a PWM controller. I'm not sure this is relevant, applicable or desired but I wanted to highlight this. > >> +            pwminv = 1; >> + > > This is silently overriding the module parameter. > > I don't think this is a good idea, at the very least not silently. > > I would suggest to add some logic in the probe function to set this value and check its consistency. > > Something like: > > """ > diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c > index 1e3c6acd89740..3a13a914e2bbb 100644 > --- a/drivers/hwmon/amc6821.c > +++ b/drivers/hwmon/amc6821.c > @@ -37,7 +37,7 @@ static const unsigned short normal_i2c[] = {0x18, 0x19, 0x1a, 0x2c, 0x2d, 0x2e, >   * Insmod parameters >   */ > > -static int pwminv;    /*Inverted PWM output. */ > +static int pwminv = -1;    /* -1 not modified by the user, 0 default PWM output, 1 inverted PWM output */ >  module_param(pwminv, int, 0444); > >  static int init = 1; /*Power-on initialization.*/ > @@ -904,6 +904,7 @@ static int amc6821_probe(struct i2c_client *client) >      struct amc6821_data *data; >      struct device *hwmon_dev; >      struct regmap *regmap; > +    bool pwminv_dt; >      int err; > >      data = devm_kzalloc(dev, sizeof(struct amc6821_data), GFP_KERNEL); > @@ -916,6 +917,18 @@ static int amc6821_probe(struct i2c_client *client) >                       "Failed to initialize regmap\n"); >      data->regmap = regmap; > > +    pwminv_dt = of_property_read_bool(client->dev.of_node, "ti,pwm-inverted"); > + > +    if (pwminv == -1) { > +        pwminv = pwminv_dt; A devicetree property, associated with a single instance of the driver, overriding a module parameter affecting all instances ? This is a no-go. Guenter