From: Guenter Roeck <linux@roeck-us.net>
To: jeroen.de_wachter.ext@nokia.com
Cc: jdelvare@suse.com, linux-hwmon@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] hwmon/tmp401: use smb word operations instead of 2 smb byte operations
Date: Mon, 9 Jan 2017 09:09:52 -0800 [thread overview]
Message-ID: <20170109170952.GB16253@roeck-us.net> (raw)
In-Reply-To: <1483980458-28202-1-git-send-email-jeroen.de_wachter.ext@nokia.com>
On Mon, Jan 09, 2017 at 05:47:37PM +0100, jeroen.de_wachter.ext@nokia.com wrote:
> From: Jeroen De Wachter <jeroen.de_wachter.ext@nokia.com>
>
> tmp401 separately read/wrote high and low bytes of temperature values while
> the hardware supports reading/writing those values in one operation. Driver
> has been modified to use word operations where possible.
>
> Tested with a tmp432 sensor on a mips64 platform.
>
> Signed-off-by: Jeroen De Wachter <jeroen.de_wachter.ext@nokia.com>
> ---
> drivers/hwmon/tmp401.c | 48 +++++++++++++++++++++++++++++-------------------
> 1 file changed, 29 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/hwmon/tmp401.c b/drivers/hwmon/tmp401.c
> index eeeed2c..88b17e4 100644
> --- a/drivers/hwmon/tmp401.c
> +++ b/drivers/hwmon/tmp401.c
> @@ -213,25 +213,29 @@ static int tmp401_update_device_reg16(struct i2c_client *client,
> for (i = 0; i < num_sensors; i++) { /* local / r1 / r2 */
> for (j = 0; j < num_regs; j++) { /* temp / low / ... */
> u8 regaddr;
> - /*
> - * High byte must be read first immediately followed
> - * by the low byte
> - */
> +
> regaddr = data->kind == tmp432 ?
> TMP432_TEMP_MSB_READ[j][i] :
> TMP401_TEMP_MSB_READ[j][i];
> - val = i2c_smbus_read_byte_data(client, regaddr);
> - if (val < 0)
> - return val;
> - data->temp[j][i] = val << 8;
> - if (j == 3) /* crit is msb only */
> - continue;
> - regaddr = data->kind == tmp432 ? TMP432_TEMP_LSB[j][i]
> - : TMP401_TEMP_LSB[j][i];
> - val = i2c_smbus_read_byte_data(client, regaddr);
> + if (j == 3) { /* crit is msb only */
> + val = i2c_smbus_read_byte_data(client, regaddr);
> + } else {
> + /*
> + * Hardware provides big endian data. However,
> + * the smbus protocol expects the LSB first in
> + * I2C_SMBUS_WORD_DATA operations.
> + * i2c_smbus_read_word_swapped swaps the bytes
> + * in the value it receives from
> + * i2c_smbus_read_word_data before returning the
> + * data, so we get the correct value.
> + */
Please drop the comment or make it shorter (such as "Hardware provides
big endian data").
> + val = i2c_smbus_read_word_swapped(client,
> + regaddr);
> + }
> if (val < 0)
> return val;
> - data->temp[j][i] |= val;
> +
> + data->temp[j][i] = j == 3 ? val << 8 : val;
> }
> }
> return 0;
> @@ -373,11 +377,17 @@ static ssize_t store_temp(struct device *dev, struct device_attribute *devattr,
>
> regaddr = data->kind == tmp432 ? TMP432_TEMP_MSB_WRITE[nr][index]
> : TMP401_TEMP_MSB_WRITE[nr][index];
> - i2c_smbus_write_byte_data(client, regaddr, reg >> 8);
> - if (nr != 3) {
> - regaddr = data->kind == tmp432 ? TMP432_TEMP_LSB[nr][index]
> - : TMP401_TEMP_LSB[nr][index];
> - i2c_smbus_write_byte_data(client, regaddr, reg & 0xFF);
> + if (nr == 3) { /* crit is msb only */
> + i2c_smbus_write_byte_data(client, regaddr, reg >> 8);
> + } else {
> + /*
> + * Hardware expects big endian data. However, the smbus protocol
> + * puts the LSB first in I2C_SMBUS_WORD_DATA operations.
> + * i2c_smbus_write_word_data_swapped will swap the bytes before
> + * passing them to i2c_smbus_write_word_data, so the hardware
> + * will receive the MSB first, as expected.
Comment in one place is enough.
Unless I am missing something, TMP432_TEMP_LSB and TMP401_TEMP_LSB are now
unused and can be removed.
Thanks,
Guenter
> + */
> + i2c_smbus_write_word_swapped(client, regaddr, reg);
> }
> data->temp[nr][index] = reg;
>
> --
> 1.8.3.1
>
next prev parent reply other threads:[~2017-01-09 17:10 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-09 16:47 [PATCH 1/2] hwmon/tmp401: use smb word operations instead of 2 smb byte operations jeroen.de_wachter.ext
2017-01-09 16:47 ` [PATCH 2/2] hwmon/tmp401: Fix some checkstyle warnings jeroen.de_wachter.ext
2017-01-09 17:11 ` Guenter Roeck
2017-01-09 17:09 ` Guenter Roeck [this message]
2017-01-09 17:55 ` [PATCH v2] hwmon/tmp401: use smb word operations instead of 2 smb byte operations jeroen.de_wachter.ext
2017-01-10 17:03 ` [v2] " Guenter Roeck
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170109170952.GB16253@roeck-us.net \
--to=linux@roeck-us.net \
--cc=jdelvare@suse.com \
--cc=jeroen.de_wachter.ext@nokia.com \
--cc=linux-hwmon@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).