On Mon, Apr 11, 2022 at 01:52:18PM +0300, Andy Shevchenko wrote: > On Mon, Apr 11, 2022 at 11:33:10AM +0300, Ilpo Järvinen wrote: > > Struct uart_port currently stores FIFO timeout. Having character > > timing information readily available is useful. Even serial core > > itself determines char_time from port->timeout using inverse > > calculation. > > > > Store frame_time directly into uart_port. Character time is stored > > in nanoseconds to have reasonable precision with high rates. > > To avoid overflow, 64-bit math is necessary. > > > > It might be possible to determine timeout from frame_time by > > multiplying it with fifosize as needed but only part of the > > users seem to be protected by a lock. Thus, this patch does > > not pursue storing only frame_time in uart_port. ... > > - char_time = (port->timeout - HZ/50) / port->fifosize; > > - char_time = char_time / 5; > > - if (char_time == 0) > > - char_time = 1; > > + char_time = max(nsecs_to_jiffies(port->frame_time / 5), 1UL); > > + > > if (timeout && timeout < char_time) > > char_time = timeout; > > Seems it can be packed to something like > > char_time = min_not_zero(nsecs_to_jiffies(port->frame_time / 5), timeout); > > ? Actually: char_time = min_not_zero(timeout, nsecs_to_jiffies(port->frame_time / 5)); Ah, either way it would still miss the case when both == 0. So, we need something like minmax3_not_zero, where 1UL is implied argument. Probably a suggesting for the future, since here it doesn't make much sense to introduce. -- With Best Regards, Andy Shevchenko
