| Message ID | 20241001062855.6928-4-kfting@nuvoton.com |
|---|---|
| State | New |
| Headers | show |
| Series | i2c: npcm: read/write operation, checkpatch | expand |
On Tue, Oct 01, 2024 at 02:28:52PM +0800, Tyrone Ting wrote: > From: Tyrone Ting <kfting@nuvoton.com> > > The users want to connect a lot of masters on the same bus. > This timeout is used to determine the time it takes to take bus ownership. > The transactions are very long, so waiting 35ms is not enough. > > Increase the timeout and treat it as the total timeout, including retries. > The total timeout is 2 seconds now. > > The i2c core layer will have chances to retry to call the i2c driver > transfer function if the i2c driver reports that the bus is busy and > returns EAGAIN. -EAGAIN ... > + /* > + * Adaptive TimeOut: estimated time in usec + 100% margin: > + * 2: double the timeout for clock stretching case > + * 9: bits per transaction (including the ack/nack) > + */ > + timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite); Side note (as I see it was in the original code), from physics point of view the USEC_PER_SEC here should be simply MICRO (as 1/Hz == s, and here it will be read as s^2 in the result), but if one finds the current more understandable, okay then.
Hi Andy: Thank you for your comments. Andy Shevchenko <andriy.shevchenko@linux.intel.com> 於 2024年10月1日 週二 下午9:14寫道： > > On Tue, Oct 01, 2024 at 02:28:52PM +0800, Tyrone Ting wrote: > > From: Tyrone Ting <kfting@nuvoton.com> > > > > The users want to connect a lot of masters on the same bus. > > This timeout is used to determine the time it takes to take bus ownership. > > The transactions are very long, so waiting 35ms is not enough. > > > > Increase the timeout and treat it as the total timeout, including retries. > > The total timeout is 2 seconds now. > > > > The i2c core layer will have chances to retry to call the i2c driver > > transfer function if the i2c driver reports that the bus is busy and > > returns EAGAIN. > > -EAGAIN > > ... > > > + /* > > + * Adaptive TimeOut: estimated time in usec + 100% margin: > > + * 2: double the timeout for clock stretching case > > + * 9: bits per transaction (including the ack/nack) > > + */ > > + timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite); > > Side note (as I see it was in the original code), from physics > point of view the USEC_PER_SEC here should be simply MICRO > (as 1/Hz == s, and here it will be read as s^2 in the result), > but if one finds the current more understandable, okay then. > I just check with Nuvoton members and they prefer the USEC_PER_SEC way. > -- > With Best Regards, > Andy Shevchenko > > Thank you. Regards, Tyrone
diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c index 7620bdcdc235..03d6c8702ecf 100644 --- a/drivers/i2c/busses/i2c-npcm7xx.c +++ b/drivers/i2c/busses/i2c-npcm7xx.c @@ -2132,19 +2132,12 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, } } - /* - * Adaptive TimeOut: estimated time in usec + 100% margin: - * 2: double the timeout for clock stretching case - * 9: bits per transaction (including the ack/nack) - */ - timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite); - timeout = max_t(unsigned long, bus->adap.timeout, usecs_to_jiffies(timeout_usec)); if (nwrite >= 32 * 1024 || nread >= 32 * 1024) { dev_err(bus->dev, "i2c%d buffer too big\n", bus->num); return -EINVAL; } - time_left = jiffies + timeout + 1; + time_left = jiffies + bus->adap.timeout / bus->adap.retries + 1; do { /* * we must clear slave address immediately when the bus is not @@ -2192,6 +2185,14 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, if (npcm_i2c_master_start_xmit(bus, slave_addr, nwrite, nread, write_data, read_data, read_PEC, read_block)) { + /* + * Adaptive TimeOut: estimated time in usec + 100% margin: + * 2: double the timeout for clock stretching case + * 9: bits per transaction (including the ack/nack) + */ + timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite); + timeout = max_t(unsigned long, bus->adap.timeout / bus->adap.retries, + usecs_to_jiffies(timeout_usec)); time_left = wait_for_completion_timeout(&bus->cmd_complete, timeout); @@ -2317,7 +2318,12 @@ static int npcm_i2c_probe_bus(struct platform_device *pdev) adap = &bus->adap; adap->owner = THIS_MODULE; adap->retries = 3; - adap->timeout = msecs_to_jiffies(35); + /* + * The users want to connect a lot of masters on the same bus. + * This timeout is used to determine the time it takes to take bus ownership. + * The transactions are very long, so waiting 35ms is not enough. + */ + adap->timeout = 2 * HZ; adap->algo = &npcm_i2c_algo; adap->quirks = &npcm_i2c_quirks; adap->algo_data = bus;