linux-kernel - Re: [PATCH] serial: mxs-auart: keep the AUART unit in reset state when not in use

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Message-ID: <1463261573.74606.1436895184420.JavaMail.open-xchange@oxbsltgw03.schlund.de>
Date:	Tue, 14 Jul 2015 19:33:04 +0200 (CEST)
From:	Stefan Wahren <stefan.wahren@...e.com>
To:	Juergen Borleis <jbe@...gutronix.de>
Cc:	linux-serial@...r.kernel.org, kernel@...gutronix.de,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: mxs-auart: keep the AUART unit in reset state
 when not in use

Hello Juergen,

> Juergen Borleis <jbe@...gutronix.de> hat am 14. Juli 2015 um 16:41
> geschrieben:
>
>
> [...]
> ---
> drivers/tty/serial/mxs-auart.c | 38 ++++++++++++++++++++++++++++++--------
> 1 file changed, 30 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
> index 13cf773..f42b6ad 100644
> --- a/drivers/tty/serial/mxs-auart.c
> +++ b/drivers/tty/serial/mxs-auart.c
> @@ -858,6 +858,30 @@ static void mxs_auart_reset(struct uart_port *u)
> writel(AUART_CTRL0_CLKGATE, u->membase + AUART_CTRL0_CLR);
> }
>
> +static void mxs_auart_do_reset(struct uart_port *u)

i think the naming of this new function is too similiar to mxs_auart_reset() and
doesn't represent the exact behavior. How about mxs_auart_keep_reset() or
mxs_auart_gate()?

> +{
> + int i;
> + u32 reg;
> +
> + reg = readl(u->membase + AUART_CTRL0);
> + /* if already in reset state, keep it untouched */
> + if (reg & AUART_CTRL0_SFTRST)
> + return;
> +
> + writel(AUART_CTRL0_CLKGATE, u->membase + AUART_CTRL0_CLR);
> + writel(AUART_CTRL0_SFTRST, u->membase + AUART_CTRL0_SET);
> +
> + for (i = 0; i < 1000; i++) {
> + reg = readl(u->membase + AUART_CTRL0);
> + /* reset is finished when the clock is gated */
> + if (reg & AUART_CTRL0_CLKGATE)
> + return;
> + udelay(10);

The delay in mxs_auart_reset() has a value of 3 microseconds. Why not the same
here?

> + }
> +
> + dev_err(u->dev, "Failed to reset the unit.");
> +}
> +
> static int mxs_auart_startup(struct uart_port *u)
> {
> int ret;
> @@ -867,7 +891,10 @@ static int mxs_auart_startup(struct uart_port *u)
> if (ret)
> return ret;
>
> - writel(AUART_CTRL0_CLKGATE, u->membase + AUART_CTRL0_CLR);
> + /* reset the unit if not aready done */

Just a typo: already?

Thanks
Stefan
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