| Message ID | 1465202936-16832-6-git-send-email-bgolaszewski@baylibre.com |
|---|---|
| State | Accepted |
| Headers | show |
> +/* > + * Both reads and writes fail if the previous write didn't complete yet. This > + * macro loops a few times waiting at least long enough for one entire page > + * write to work. > + * > + * It takes two parameters: a variable in which the future timeout in jiffies > + * will be stored and a temporary variable holding the time of the last > + * iteration of processing the request. Both should be unsigned integers > + * holding at least 32 bits. > + */ > +#define loop_until_timeout(tout, op_time) \ > + for (tout = jiffies + msecs_to_jiffies(write_timeout), \ > + op_time = jiffies; \ > + time_before(op_time, tout); \ > + usleep_range(1000, 1500), op_time = jiffies) There is one subtle change coming with this change: the do-while loop is guaranteed to run at least once while the for-loop doesn't.
2016-07-15 14:24 GMT+02:00 Wolfram Sang <wsa@the-dreams.de>: >> +/* >> + * Both reads and writes fail if the previous write didn't complete yet. This >> + * macro loops a few times waiting at least long enough for one entire page >> + * write to work. >> + * >> + * It takes two parameters: a variable in which the future timeout in jiffies >> + * will be stored and a temporary variable holding the time of the last >> + * iteration of processing the request. Both should be unsigned integers >> + * holding at least 32 bits. >> + */ >> +#define loop_until_timeout(tout, op_time) \ >> + for (tout = jiffies + msecs_to_jiffies(write_timeout), \ >> + op_time = jiffies; \ >> + time_before(op_time, tout); \ >> + usleep_range(1000, 1500), op_time = jiffies) > > There is one subtle change coming with this change: the do-while loop is > guaranteed to run at least once while the for-loop doesn't. > While it's technically possible, it will never happen as long as write_timeout is set to some sensible value. Thanks, Bartosz -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> >> +#define loop_until_timeout(tout, op_time) \ > >> + for (tout = jiffies + msecs_to_jiffies(write_timeout), \ > >> + op_time = jiffies; \ > >> + time_before(op_time, tout); \ > >> + usleep_range(1000, 1500), op_time = jiffies) > > > > There is one subtle change coming with this change: the do-while loop is > > guaranteed to run at least once while the for-loop doesn't. > > > > While it's technically possible, it will never happen as long as > write_timeout is set to some sensible value. I know that. I prefer Linux to be rock-stable, though, even when slightly misconfigured (or under extreme load for that matter). An incremental patch would be enough, no need to resend.
> > >> +#define loop_until_timeout(tout, op_time) \ > > >> + for (tout = jiffies + msecs_to_jiffies(write_timeout), \ > > >> + op_time = jiffies; \ > > >> + time_before(op_time, tout); \ > > >> + usleep_range(1000, 1500), op_time = jiffies) What about: #define loop_until_timeout(tout, op_time) \ for (tout = jiffies + msecs_to_jiffies(write_timeout), op_time = 0; \ op_time ? time_before(op_time, tout) : true; \ usleep_range(1000, 1500), op_time = jiffies) ? Would probably need an explanation in a comment, though.
2016-07-16 6:56 GMT+02:00 Wolfram Sang <wsa@the-dreams.de>: > >> > >> +#define loop_until_timeout(tout, op_time) \ >> > >> + for (tout = jiffies + msecs_to_jiffies(write_timeout), \ >> > >> + op_time = jiffies; \ >> > >> + time_before(op_time, tout); \ >> > >> + usleep_range(1000, 1500), op_time = jiffies) > > What about: > > #define loop_until_timeout(tout, op_time) \ > for (tout = jiffies + msecs_to_jiffies(write_timeout), op_time = 0; \ > op_time ? time_before(op_time, tout) : true; \ > usleep_range(1000, 1500), op_time = jiffies) > > ? Would probably need an explanation in a comment, though. > Hi Wolfram, thanks for the suggestion, it looks good. I'm not at home right now and don't have access to any device with which I could test it. I'll try to send the patch tomorrow evening or Monday morning. Best regards, Bartosz Golaszewski -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> thanks for the suggestion, it looks good. I'm not at home right now > and don't have access to any device with which I could test it. I'll > try to send the patch tomorrow evening or Monday morning. Thanks. Please make it an incremental patch because I am going to apply the base patches right now.
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c index 0621937..2efb572 100644 --- a/drivers/misc/eeprom/at24.c +++ b/drivers/misc/eeprom/at24.c @@ -113,6 +113,22 @@ MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)"); ((1 << AT24_SIZE_FLAGS | (_flags)) \ << AT24_SIZE_BYTELEN | ilog2(_len)) +/* + * Both reads and writes fail if the previous write didn't complete yet. This + * macro loops a few times waiting at least long enough for one entire page + * write to work. + * + * It takes two parameters: a variable in which the future timeout in jiffies + * will be stored and a temporary variable holding the time of the last + * iteration of processing the request. Both should be unsigned integers + * holding at least 32 bits. + */ +#define loop_until_timeout(tout, op_time) \ + for (tout = jiffies + msecs_to_jiffies(write_timeout), \ + op_time = jiffies; \ + time_before(op_time, tout); \ + usleep_range(1000, 1500), op_time = jiffies) + static const struct i2c_device_id at24_ids[] = { /* needs 8 addresses as A0-A2 are ignored */ { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) }, @@ -225,14 +241,7 @@ static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf, msg[1].len = count; } - /* - * Reads fail if the previous write didn't complete yet. We may - * loop a few times until this one succeeds, waiting at least - * long enough for one entire page write to work. - */ - timeout = jiffies + msecs_to_jiffies(write_timeout); - do { - read_time = jiffies; + loop_until_timeout(timeout, read_time) { if (at24->use_smbus) { status = i2c_smbus_read_i2c_block_data_or_emulated(client, offset, count, buf); @@ -246,9 +255,7 @@ static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf, if (status == count) return count; - - usleep_range(1000, 1500); - } while (time_before(read_time, timeout)); + } return -ETIMEDOUT; } @@ -299,14 +306,7 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf, msg.len = i + count; } - /* - * Writes fail if the previous one didn't complete yet. We may - * loop a few times until this one succeeds, waiting at least - * long enough for one entire page write to work. - */ - timeout = jiffies + msecs_to_jiffies(write_timeout); - do { - write_time = jiffies; + loop_until_timeout(timeout, write_time) { if (at24->use_smbus_write) { switch (at24->use_smbus_write) { case I2C_SMBUS_I2C_BLOCK_DATA: @@ -331,9 +331,7 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf, if (status == count) return count; - - usleep_range(1000, 1500); - } while (time_before(write_time, timeout)); + } return -ETIMEDOUT; }
Before splitting the read/write routines into smaller, more specialized functions, unduplicate some code in advance. Use a 'for' loop instead of 'do while' when waiting for the previous write to complete and hide it behind a macro. Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com> --- drivers/misc/eeprom/at24.c | 42 ++++++++++++++++++++---------------------- 1 file changed, 20 insertions(+), 22 deletions(-)