Messages in this thread | | | Date | Fri, 06 Mar 2015 11:50:18 -0500 | From | Peter Hurley <> | Subject | Re: [RFC] With 8250 Designware UART, if writes to the LCR failed the kernel will hung up |
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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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