Hi Shimoda-san,
On Tue, Jun 21, 2016 at 9:35 AM, Yoshihiro Shimoda
<yoshihiro.shimoda.uh@xxxxxxxxxxx> 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
>> <koji.matsuoka.xm@xxxxxxxxxxx>.
>>
>> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
>> ---
>> 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?
> +
> serial_port_out(port, SCSCR, ctrl_temp);
>
> uart_console_write(port, s, count, serial_console_putchar);
Thanks for your report!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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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