On Mon, Apr 11, 2022 at 01:56:24PM +0300, Andy Shevchenko wrote: > 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. In case somebody goes for it: #define minmax_not_zero(x, y) (min_not_zero(x, y) ?: 1) -- With Best Regards, Andy Shevchenko
