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
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