On Thu, May 07, 2020 at 02:31:35AM +0300, Serge Semin wrote: > The race condition may happen if the UART reference clock is shared with > some other device (on Baikal-T1 SoC it's another DW UART port). In this > case if that device changes the clock rate while serial console is using > it the DW 8250 UART port might not only end up with an invalid uartclk > value saved, but may also experience a distorted output data since > baud-clock could have been changed. In order to fix this lets at least > try to adjust the 8250 port setting like UART clock rate in case if the > reference clock rate change is discovered. The driver will call the new > method to update 8250 UART port clock rate settings. It's done by means of > the clock event notifier registered at the port startup and unregistered > in the shutdown callback method. I'm wondering if clock framework itself can provide such a notifier? > Note 1. In order to avoid deadlocks we had to execute the UART port update > method in a dedicated deferred work. This is due to (in my opinion > redundant) the clock update implemented in the dw8250_set_termios() > method. So, and how you propose to update the clock when ->set_termios() is called? > Note 2. Before the ref clock is manually changed by the custom > set_termios() function we swap the port uartclk value with new rate > adjusted to be suitable for the requested baud. It is necessary in > order to effectively disable a functionality of the ref clock events > handler for the current UART port, since uartclk update will be done > a bit further in the generic serial8250_do_set_termios() function. ... > + struct notifier_block clk_notifier; > + struct work_struct clk_work; Oh, this seems too much. Perhaps, the compatible based quirk with your initial approach is much better for time being. -- With Best Regards, Andy Shevchenko
