On Thu, 2018-07-05 at 14:54 +0800, Jisheng Zhang wrote: > On Thu, 5 Jul 2018 14:39:21 +0800 Jisheng Zhang wrote: > > <snip> > > > > > > > > + serial_port_out(p, UART_LCR, up->lcr | UART_LCR_DLAB); > > > > + serial_dl_write(up, quot); > > > > > > At some point it would be a helper, I think. We can call > > > serial8250_do_set_divisor() here. So, perhaps we might export > > > it. > > > > serial8250_do_set_divisor will drop the frac, that's not we want ;) > > > > And most importantly, serial8250_do_set_divisor() will set a wrong > BRD(I) > for fractional capable DW uarts. For example, clk = 25MHZ, baud = > 115200. > > In fractional capable DW uarts, we should set BRD(I) as > 25000000/(16*115200) = 13 > > but serial8250_do_set_divisor() will set BRD(I) as > DIV_ROUND_CLOSEST(25*1000000, 16*115200)) = 14 How come? It doesn't do any calculus (for DW 8250), it just writes few registers based on input. -- Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> Intel Finland Oy -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
