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From: Stefan Agner <stefan@agner.ch>
To: u.kleine-koenig@pengutronix.de
Cc: gregkh@linuxfoundation.org, jslaby@suse.com,
	linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] serial: imx: fix cached UCR2 read on software reset
Date: Thu, 19 Apr 2018 23:37:23 +0200	[thread overview]
Message-ID: <581f0f26d7191aa3355a6c63b531f876@agner.ch> (raw)
In-Reply-To: <20180416153502.11814-1-stefan@agner.ch>

Hi Uwe,

On 16.04.2018 17:35, Stefan Agner wrote:
> To reset the UART the SRST needs be cleared (low active). According
> to the documentation the bit will remain active for 4 module clocks
> until it is cleared (set to 1).
> 
> Hence the real register need to be read in case the cached register
> indcates that the SRST bit is zero.
> 
> This bug lead to wrong baudrate because the baud rate register got
> restored before reset completed in imx_flush_buffer.

Given that you reviewed my other patch rather quickly, you might have
overlooked this one?

Since it is a regression, this should go into v4.17 still...

--
Stefan

> 
> Fixes: 3a0ab62f43de ("serial: imx: implement shadow registers for UCRx
> and UFCR")
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---
>  drivers/tty/serial/imx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 91f3a1a5cb7f..4ff6bd6eb9ab 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -316,7 +316,7 @@ static u32 imx_uart_readl(struct imx_port *sport,
> u32 offset)
>  		 * differ from the value that was last written. As it only
>  		 * clears after being set, reread conditionally.
>  		 */
> -		if (sport->ucr2 & UCR2_SRST)
> +		if (!(sport->ucr2 & UCR2_SRST))
>  			sport->ucr2 = readl(sport->port.membase + offset);
>  		return sport->ucr2;
>  		break;

  reply	other threads:[~2018-04-19 21:37 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-16 15:35 Stefan Agner
2018-04-19 21:37 ` Stefan Agner [this message]
2018-04-20  6:03   ` Uwe Kleine-König
2018-04-20  8:22     ` Stefan Agner
2018-04-19 22:15 ` Fabio Estevam

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