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Mon, 05 Apr 2021 14:41:19 -0700 (PDT) Sender: Guenter Roeck Subject: Re: [PATCH] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond To: Konstantin Aladyshev Cc: kunyi@google.com, Konstantin Aladyshev , Jean Delvare , linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210401214543.4073-1-aladyshev22@gmail.com> 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= Message-ID: Date: Mon, 5 Apr 2021 14:41:17 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210401214543.4073-1-aladyshev22@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/1/21 2:45 PM, Konstantin Aladyshev wrote: > From: Konstantin Aladyshev > > SBTSI sensors don't work when the CPU is off. > In this case every 'i2c_smbus_read_byte_data' function would fail > by a timeout. > Currently temp1_max/temp1_min file reads can cause two such timeouts > for every read. > Restructure code so there will be no more than one timeout for every > read opeartion. > operation > Signed-off-by: Konstantin Aladyshev > --- > drivers/hwmon/sbtsi_temp.c | 59 +++++++++++++++++++------------------- > 1 file changed, 29 insertions(+), 30 deletions(-) > > diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c > index e35357c48b8e..e09a8cf6de45 100644 > --- a/drivers/hwmon/sbtsi_temp.c > +++ b/drivers/hwmon/sbtsi_temp.c > @@ -74,53 +74,52 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type, > u32 attr, int channel, long *val) > { > struct sbtsi_data *data = dev_get_drvdata(dev); > + u8 temp_int_reg, temp_dec_reg; > s32 temp_int, temp_dec; > int err; > > switch (attr) { > case hwmon_temp_input: > - /* > - * ReadOrder bit specifies the reading order of integer and > - * decimal part of CPU temp for atomic reads. If bit == 0, > - * reading integer part triggers latching of the decimal part, > - * so integer part should be read first. If bit == 1, read > - * order should be reversed. > - */ > - err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG); > - if (err < 0) > - return err; > - > - mutex_lock(&data->lock); > - if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) { > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC); > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT); > - } else { > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT); > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC); > - } > - mutex_unlock(&data->lock); > + temp_int_reg = SBTSI_REG_TEMP_INT; > + temp_dec_reg = SBTSI_REG_TEMP_DEC; > break; > case hwmon_temp_max: > - mutex_lock(&data->lock); > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT); > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC); > - mutex_unlock(&data->lock); > + temp_int_reg = SBTSI_REG_TEMP_HIGH_INT; > + temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC; > break; > case hwmon_temp_min: > - mutex_lock(&data->lock); > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT); > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC); > - mutex_unlock(&data->lock); > + temp_int_reg = SBTSI_REG_TEMP_LOW_INT; > + temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC; > break; > default: > return -EINVAL; > } > > + /* > + * ReadOrder bit specifies the reading order of integer and > + * decimal part of CPU temp for atomic reads. If bit == 0, > + * reading integer part triggers latching of the decimal part, > + * so integer part should be read first. If bit == 1, read > + * order should be reversed. > + */ > + err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG); > + if (err < 0) > + return err; > + It seems the "fix" is to always execute above code, which presumably fails if the CPU is off. The downside of this approach is that it forces an unnecessary extra and unnecessary i2c operation when reading the limits. The real fix would be to check for error after each i2c operation, not only after both operations are complete. > + mutex_lock(&data->lock); > + if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) { > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg); > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg); > + } else { > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg); > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg); > + } > + mutex_unlock(&data->lock); > > - if (temp_int < 0) > - return temp_int; > if (temp_dec < 0) > return temp_dec; > + if (temp_int < 0) > + return temp_int; I don't see a value in swapping the checks. Guenter > > *val = sbtsi_reg_to_mc(temp_int, temp_dec); > >