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([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-73905fd7a3fsm12903893b3a.67.2025.03.26.09.49.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Mar 2025 09:49:05 -0700 (PDT) Sender: Guenter Roeck Message-ID: Date: Wed, 26 Mar 2025 09:49:04 -0700 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] hwmon: (max6639) : Allow setting target RPM To: Naresh Solanki Cc: Jean Delvare , linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250324185744.2421462-1-you@example.com> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/26/25 09:36, Naresh Solanki wrote: > Hi Guenter, > > On Tue, 25 Mar 2025 at 05:00, Guenter Roeck wrote: >> >> On 3/24/25 11:57, Your Name wrote: >>> From: Naresh Solanki >>> >>> Currently, during startup, the fan is set to its maximum RPM by default, >>> which may not be suitable for all use cases. >>> This patch introduces support for specifying a target RPM via the Device >>> Tree property "target-rpm". >>> >>> Changes: >>> - Added `target_rpm` field to `max6639_data` structure to store the >>> target RPM for each fan channel. >>> - Modified `max6639_probe_child_from_dt()` to read the `"target-rpm"` >>> property from the Device Tree and set `target_rpm` accordingly. >>> - Updated `max6639_init_client()` to use `target_rpm` to compute the >>> initial PWM duty cycle instead of defaulting to full speed (120/120). >>> >>> Behavior: >>> - If `"target-rpm"` is specified, the fan speed is set accordingly. >>> - If `"target-rpm"` is not specified, the previous behavior (full speed >>> at startup) is retained. >>> >> >> Unless I am missing something, that is not really correct. See below. >> >>> This allows better control over fan speed during system initialization. >>> >>> Signed-off-by: Naresh Solanki >>> --- >>> drivers/hwmon/max6639.c | 15 ++++++++++++--- >>> 1 file changed, 12 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/hwmon/max6639.c b/drivers/hwmon/max6639.c >>> index 32b4d54b2076..ca8a8f58d133 100644 >>> --- a/drivers/hwmon/max6639.c >>> +++ b/drivers/hwmon/max6639.c >>> @@ -80,6 +80,7 @@ struct max6639_data { >>> /* Register values initialized only once */ >>> u8 ppr[MAX6639_NUM_CHANNELS]; /* Pulses per rotation 0..3 for 1..4 ppr */ >>> u8 rpm_range[MAX6639_NUM_CHANNELS]; /* Index in above rpm_ranges table */ >>> + u32 target_rpm[MAX6639_NUM_CHANNELS]; >>> >>> /* Optional regulator for FAN supply */ >>> struct regulator *reg; >>> @@ -560,8 +561,14 @@ static int max6639_probe_child_from_dt(struct i2c_client *client, >>> } >>> >> >> target_rpm[] is 0 here. >> >>> err = of_property_read_u32(child, "max-rpm", &val); >>> - if (!err) >>> + if (!err) { >>> data->rpm_range[i] = rpm_range_to_reg(val); >>> + data->target_rpm[i] = val; >>> + } >> >> If there is no max-rpm property, or if there is no devicetree support, >> target_rpm[i] is still 0. >> >>> + >>> + err = of_property_read_u32(child, "target-rpm", &val); >>> + if (!err) >>> + data->target_rpm[i] = val; >> >> If there is neither max-rpm nor target-rpm, target_rpm[i] is still 0. >> >>> >>> return 0; >>> } >>> @@ -573,6 +580,7 @@ static int max6639_init_client(struct i2c_client *client, >>> const struct device_node *np = dev->of_node; >>> struct device_node *child; >>> int i, err; >>> + u8 target_duty; >>> >>> /* Reset chip to default values, see below for GCONFIG setup */ >>> err = regmap_write(data->regmap, MAX6639_REG_GCONFIG, MAX6639_GCONFIG_POR); >>> @@ -639,8 +647,9 @@ static int max6639_init_client(struct i2c_client *client, >>> if (err) >>> return err; >>> >>> - /* PWM 120/120 (i.e. 100%) */ >>> - err = regmap_write(data->regmap, MAX6639_REG_TARGTDUTY(i), 120); >>> + /* Set PWM based on target RPM if specified */ >>> + target_duty = 120 * data->target_rpm[i] / rpm_ranges[data->rpm_range[i]]; >> >> If there is no devicetree support, or if neither max-rpm nor target-rpm are >> provided, target_duty will be 0, and the fans will stop. >> >> Maybe my interpretation is wrong, but I think both target_rpm[] and rpm_range[] >> will need to be initialized. Also, it seems to me that there will need to be an >> upper bound for target_rpm[]; without it, it is possible that target_duty > 120, >> which would probably not be a good idea. > Yes you're right. I missed it in my analysis. > > Here is the logic that would address: > target_rpm = 120; > /* Set PWM based on target RPM if specified */ > if (data->target_rpm[i] != 0 && > data->target_rpm[i] <= rpm_ranges[data->rpm_range[i]]) { > > target_duty = 120 * data->target_rpm[i] / > rpm_ranges[data->rpm_range[i]]; > } > > Please let me know your thoughts & suggestions. > I would prefer if target_rpm[] and rpm_range[] were pre-initialized with default values in the probe function. That would avoid runtime checks. Thanks, Guenter