Geert Uytterhoeven
geert****@linux*****
2017年 7月 11日 (火) 19:46:15 JST
Hi Rob, On Tue, Jul 11, 2017 at 12:37 PM, Rob Landley <rob****@landl*****> wrote: > On 07/11/2017 03:59 AM, Geert Uytterhoeven wrote: >> On Tue, Jul 11, 2017 at 10:42 AM, Arnd Bergmann <arnd****@arndb*****> wrote: >>> On Tue, Jul 11, 2017 at 8:59 AM, Geert Uytterhoeven >>> <geert****@linux*****> wrote: >>>> On Tue, Jul 11, 2017 at 5:38 AM, Magnus Damm <magnu****@gmail*****> wrote: >>>>> On Mon, Jul 10, 2017 at 10:28 PM, Geert Uytterhoeven >>>>> Since enabling DMA Engine still keeps PIO support around I wonder why >>>>> we need this Kconfig at all - other drivers seem to get by without >>>>> this kind of thing? >>>>> So in my opinion it would also be nice to get rid of SERIAL_SH_SCI_DMA >>>>> completely and reducing the number of special per-driver Kconfig >>>>> entries. >>>> >>>> In general, I would agree, and remove the option at the blimp of an eye. >>>> However, this driver is shared with H8/300 and SuperH. While both could use >>>> DMA (but it's not supported by Linux yet), I don't know if they are willing to >>>> live with the increased static and dynamic memory footprint of SH_SCI DMA >>>> support. >>> >>> One more thing: enabling the DMA support in the console driver generally >>> means you cannot use printk in the DMA driver anywhere that may be called >>> during printk(). Not sure if that is a concern here. >> >> Not anymore, as all of these prints should have been removed/disabled already. > > Last I checked qemu-system-sh4 still doesn't work with current linux > serial driver unless you do: > > --- a/drivers/tty/serial/sh-sci.c > +++ b/drivers/tty/serial/sh-sci.c > @@ -2193,7 +2193,7 @@ static void sci_reset(struct uart_port *port) > setup_timer(&s->rx_fifo_timer, rx_fifo_timer_fn, > (unsigned long)s); > } else { > - if (port->type == PORT_SCIFA || > + if (1 || port->type == PORT_SCIFA || > port->type == PORT_SCIFB) > scif_set_rtrg(port, 1); > else > > Does this DMA stuff make that situation worse? No, SH-SCI DMA is not used on your platform. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert****@linux***** In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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