Re: [PATCH] serial: imx: fix cached UCR2 read on software reset
From: Stefan Agner
Date: Thu Apr 19 2018 - 17:37:34 EST
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...
> Fixes: 3a0ab62f43de ("serial: imx: implement shadow registers for UCRx
> and UFCR")
> Signed-off-by: Stefan Agner <stefan@xxxxxxxx>
> 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;