Hi Shimoda-san,
On Thu, Jun 23, 2016 at 12:42 PM, Yoshihiro Shimoda
<[email protected]> wrote:
>> From: Geert Uytterhoeven
>> Sent: Tuesday, June 21, 2016 11:52 PM
>> On Tue, Jun 21, 2016 at 9:35 AM, Yoshihiro Shimoda
>> <[email protected]> wrote:
>> >> From: Geert Uytterhoeven
>> >> Sent: Friday, May 27, 2016 3:19 AM
>> >>
>> >> Make sure the transmitter and receiver are stopped when shutting down
>> >> the port, and related interrupts are disabled.
>> >>
>> >> Without this:
>> >> - New input data may be received into the RX FIFO, possibly
>> >> triggering a new RX DMA completion,
>> >> - Transfers will still be enabled on a subsequent startup of the UART,
>> >> before the UART's FIFOs have been reset, causing reading of stale
>> >> data.
>> >>
>> >> Inspired by a patch in the BSP by Koji Matsuoka
>> >> <[email protected]>.
>> >>
>> >> Signed-off-by: Geert Uytterhoeven <[email protected]>
>> >> ---
>> >> Extracted from "[PATCH/RFC v3 0/4] serial: sh-sci: Add DT DMA support".
>> >> The issues with the serial console seen before on r8a7740/armadillo and
>> >> sh73a0/kzm9g seem to be gone.
>> >>
>> >> Changes after resurrection:
>> >> - Write zero to also disable related interrupts, as suggested by
>> >> Laurent Pinchart,
>> >
>> > If we write zero to the register, we cannot use the port as a console
>> > after it is called.
>> > In fact, I have an issue while rc scripts are running on my root
>> > filesystem.
>> > When rc scripts is running, "shutdown" is called a lot.
>> > After the "shutdown", if the kernel will put strings using a console, it
>> > cannot put strings
>> > because the register is zero (TE and CKE are 0). So, we have to consider
>> > it.
>> >
>> > FYI, I made a patch to fix this issue.
>> > (Perhaps, both the CKE and TE should be set in the serial_console_write(),
>> > but I don't know how to set the CKE for now :) )
>> >
>> > Best regards,
>> > Yoshihiro Shimoda
>> > ---
>> > diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
>> > index afa25ec..b5b1b38 100644
>> > --- a/drivers/tty/serial/sh-sci.c
>> > +++ b/drivers/tty/serial/sh-sci.c
>> > @@ -1989,6 +1989,7 @@ static void sci_shutdown(struct uart_port *port)
>> > {
>> > struct sci_port *s = to_sci_port(port);
>> > unsigned long flags;
>> > + unsigned int ctrl;
>> >
>> > dev_dbg(port->dev, "%s(%d)\n", __func__, port->line);
>> >
>> > @@ -1998,8 +1999,12 @@ static void sci_shutdown(struct uart_port *port)
>> > spin_lock_irqsave(&port->lock, flags);
>> > sci_stop_rx(port);
>> > sci_stop_tx(port);
>> > - /* Stop RX and TX, disable related interrupts */
>> > - serial_port_out(port, SCSCR, 0);
>> > + /* Stop RX and TX, disable related interrupts, keep clock source */
>> > + ctrl = serial_port_in(port, SCSCR);
>> > + ctrl = (s->cfg->scscr & ~(SCSCR_CKE1 | SCSCR_CKE0)) |
>> > + (ctrl & (SCSCR_CKE1 | SCSCR_CKE0));
>>
>> My bad. We should indeed keep CKE, as the serial console relies on that.
>> I'm just wondering why I didn't notice this, as at least on Koelsch, the
>> external SCIF clock is used, implying a non-zero CKEx setting.
>>
>> > + serial_port_out(port, SCSCR, ctrl);
>> > +
>> > spin_unlock_irqrestore(&port->lock, flags);
>> >
>> > #ifdef CONFIG_SERIAL_SH_SCI_DMA
>> > @@ -2801,6 +2806,8 @@ static void serial_console_write(struct console *co,
>> > const char *s,
>> > ctrl = serial_port_in(port, SCSCR);
>> > ctrl_temp = (sci_port->cfg->scscr & ~(SCSCR_CKE1 | SCSCR_CKE0)) |
>> > (ctrl & (SCSCR_CKE1 | SCSCR_CKE0));
>> > + ctrl_temp |= SCSCR_TE; /* FIXME: while "break ctl" is on */
>>
>> This shouldn't be needed, as SCSCR_TE should be set in sci_port->cfg->scscr
>> (look in all places where it's initialized).
>> Can you please double check?
>
> Sorry for the check (because I took a day off yesterday).
> As you mentioned it, this is not needed.
> (I should have tested on such a code before I sent this report...)
Thanks, I will send an updated patch shortly.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
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
