From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Magnus Damm <magnus.damm@gmail.com>
Cc: Linux-Renesas <linux-renesas-soc@vger.kernel.org>
Subject: Re: [PATCH/RFC] serial: sh-sci: Update uartclk based on selected clock
Date: Fri, 7 Feb 2020 12:54:29 +0100 [thread overview]
Message-ID: <CAMuHMdWJgos4540rhj54EmVKX+QCtAwXLWMH7mL286UUuv9HaA@mail.gmail.com> (raw)
In-Reply-To: <156630351537.24954.2550542042474735517.sendpatchset@octo>
Hi Magnus,
On Tue, Aug 20, 2019 at 2:16 PM Magnus Damm <magnus.damm@gmail.com> wrote:
> From: Magnus Damm <damm+renesas@opensource.se>
>
> I noticed that uartclk never gets updated as it is today.
>
> This compile tested patch makes sure uartclk is in sync with
> whatever clock is selected during sci_set_termios(). Exposing
> the actual value to user space seems like a good plan to me.
Except that it changes all the time.
What is userspace supposed to do with this value?
Support the deprecated UPF_SPD_CUST flag?
Anything else?
See also "[PATCH] serial: sh-sci: Support custom speed setting"
https://lore.kernel.org/linux-renesas-soc/20200129161955.30562-1-erosca@de.adit-jv.com/
> --- 0001/drivers/tty/serial/sh-sci.c
> +++ work/drivers/tty/serial/sh-sci.c 2019-08-20 20:32:17.680030451 +0900
> @@ -129,6 +129,7 @@ struct sci_port {
> /* Clocks */
> struct clk *clks[SCI_NUM_CLKS];
> unsigned long clk_rates[SCI_NUM_CLKS];
> + int sel_clk;
>
> int irqs[SCIx_NR_IRQS];
> char *irqstr[SCIx_NR_IRQS];
> @@ -542,7 +543,11 @@ static void sci_port_enable(struct sci_p
> clk_prepare_enable(sci_port->clks[i]);
> sci_port->clk_rates[i] = clk_get_rate(sci_port->clks[i]);
> }
> - sci_port->port.uartclk = sci_port->clk_rates[SCI_FCK];
> +
> + if (sci_port->sel_clk >= 0)
> + sci_port->port.uartclk = sci_port->clk_rates[sci_port->sel_clk];
> + else
> + sci_port->port.uartclk = sci_port->clk_rates[SCI_FCK];
> }
Iff this is worthwhile, I think it's better to use the highest rate of all
available clock inputs, as that gives a hint about the maximum usable
speed.
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
prev parent reply other threads:[~2020-02-07 11:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-20 12:18 [PATCH/RFC] serial: sh-sci: Update uartclk based on selected clock Magnus Damm
2019-08-29 9:21 ` Geert Uytterhoeven
2020-02-07 11:54 ` Geert Uytterhoeven [this message]
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