From: Peter Hurley <peter@hurleysoftware.com>
To: Zhang Zhen <zhenzhang.zhang@huawei.com>
Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
tim.kryger@linaro.org, gregkh@linuxfoundation.org,
jamie@jamieiles.com, alan@linux.intel.com, arnd@arndb.de,
shenjiangjiang@huawei.com, long.wanglong@huawei.com
Subject: Re: [RFC] With 8250 Designware UART, if writes to the LCR failed the kernel will hung up
Date: Fri, 06 Mar 2015 11:50:18 -0500 [thread overview]
Message-ID: <54F9DACA.3020103@hurleysoftware.com> (raw)
In-Reply-To: <54F96F5B.2090601@huawei.com>
Hi Zhang,
On 03/06/2015 04:11 AM, Zhang Zhen wrote:
> Hi,
>
> I'm testing 4.0-rc1 kernel on my board with 8250 Designware UART.(ARM Cortex-a15 single core).
>
> I found if serial is busy and writes to the LCR failed after tried 1000 times.
> The kernel will hung up.
>
> The system boot success after changed from:
>
> 95 static void dw8250_serial_out(struct uart_port *p, int offset, int value)
> 96 {
> 97 struct dw8250_data *d = p->private_data;
> 98
> ...
> ...
> 112 writeb(value, p->membase + (UART_LCR << p->regshift));
> 113 }
> 114 dev_err(p->dev, "Couldn't set LCR to %d\n", value);
> 115 }
> 116 }
>
> to:
>
> 95 static void dw8250_serial_out(struct uart_port *p, int offset, int value)
> 96 {
> 97 struct dw8250_data *d = p->private_data;
> 98
> ...
> ...
> 112 writeb(value, p->membase + (UART_LCR << p->regshift));
> 113 }
> 114 dev_info(p->dev, "Couldn't set LCR to %d\n", value); //changed here
> 115 }
> 116 }
>
> The reason is serial8250_console_write can't get port->lock because serial8250_do_set_termios has
> got port->lock.
> So i think here we should change from dev_err to dev_info ?
That's not really going to help because this will still hang if the
console_loglevel is set to < KERN_INFO.
> Any suggestions are welcome.
Check that the port is not the uart_console() before logging the error,
like;
if (!uart_console(p))
dev_err(p->dev, "Couldn't .....");
Use a global flag to note the error and check it from other contexts.
Plus, find out why you can't write LCR there.
Also, consider re-designing how the 8250_dw driver implements that
"feature".
Regards,
Peter Hurley
next prev parent reply other threads:[~2015-03-06 16:50 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-06 9:11 [RFC] With 8250 Designware UART, if writes to the LCR failed the kernel will hung up Zhang Zhen
2015-03-06 16:50 ` Peter Hurley [this message]
2015-03-07 3:01 ` Tim Kryger
2015-03-09 7:10 ` long.wanglong
2015-03-09 13:32 ` Alan Cox
2015-03-09 14:36 ` Tim Kryger
2015-03-09 15:05 ` Alan Cox
2015-03-10 2:47 ` Tim Kryger
2015-03-10 3:15 ` Zhang Zhen
2015-03-10 13:25 ` Peter Hurley
2015-03-11 1:20 ` Zhang Zhen
2015-03-13 15:36 ` Andy Shevchenko
2015-03-15 14:50 ` Peter Hurley
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