Messages in this thread | | | Date | Thu, 27 Jan 2011 12:30:36 -0800 | From | Saravana Kannan <> | Subject | Re: Locking in the clk API |
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On 01/27/2011 12:54 AM, Russell King - ARM Linux wrote: > On Wed, Jan 26, 2011 at 08:34:20PM -0800, Saravana Kannan wrote: >> I'm not too familiar with serial/tty, does anyone know if the >> .set_termios needs to be atmoic? If not, we could just change >> cpm_uart/cpm_uart_core.c to use mutex instead of spinlock. > > The locking is there to protect against the interrupt handler accessing > the port->* stuff (which seems to have been forgotten by the cpm driver). > > I don't see any reason why clk_set_rate() needs to be under the spinlock > there - we need the reprogramming of the baud rate within the spinlock > on 8250 because of DLAB bit hiding the data registers. It's also a good > idea that it _is_ within the spinlock along with uart_update_timeout() > to ensure timeouts and the baud rate are updated together.
For internal tree purposes, does .set_termios need to be atomic? Can it grab mutexes instead of spinlock?
Going back to the topic, how about CPU freq drivers possibly using clk_set_rate() to change freq? Do you think that's not the case or a concern?
All,
Do any one of your mach's control CPU freq using clk_set_rate() and does it need to be atomic? CPUfreq doesn't need it to be atomic. So, you will need clk_set_rate() to be atomic only if you try to use it to lower CPU freq very late during idle/suspend.
-Saravana
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