| Message ID | 95cf2c11-c7db-bdff-7165-282586e08b19@landley.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Rob, On Tue, Jul 11, 2017 at 12:37 PM, Rob Landley <rob@landley.net> wrote: > On 07/11/2017 03:59 AM, Geert Uytterhoeven wrote: >> On Tue, Jul 11, 2017 at 10:42 AM, Arnd Bergmann <arnd@arndb.de> wrote: >>> On Tue, Jul 11, 2017 at 8:59 AM, Geert Uytterhoeven >>> <geert@linux-m68k.org> wrote: >>>> On Tue, Jul 11, 2017 at 5:38 AM, Magnus Damm <magnus.damm@gmail.com> 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-m68k.org 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
On 07/11/2017 05:46 AM, Geert Uytterhoeven wrote: > Hi Rob, > > On Tue, Jul 11, 2017 at 12:37 PM, Rob Landley <rob@landley.net> wrote: >> On 07/11/2017 03:59 AM, Geert Uytterhoeven wrote: >>> On Tue, Jul 11, 2017 at 10:42 AM, Arnd Bergmann <arnd@arndb.de> wrote: >>>> On Tue, Jul 11, 2017 at 8:59 AM, Geert Uytterhoeven >>>> <geert@linux-m68k.org> wrote: >>>>> On Tue, Jul 11, 2017 at 5:38 AM, Magnus Damm <magnus.damm@gmail.com> 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, This issue is still there. QEMU's serial output is borked with the last year's worth of vanilla superh kernels. Rob
--- 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