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SubjectRe: dw8250_set_termios() questions
Heikki, ping.

On 07/11/2014 07:57 AM, Alex Elder wrote:
> Heikki, I have not been a subscriber of the linux-serial
> mailing list and didn't see this patch go by:
> serial: 8250_dw: clock rate handling for all ACPI platforms
> http://www.spinics.net/lists/linux-serial/msg12861.html
>
> I had been working on doing something very similar for some
> Broadcom device tree based devices and it might have been
> helpful for me to have seen it. What I ended up with was
> *very* similar to what you did. Here is the last version
> of the patch I posted:
> https://lkml.org/lkml/2014/7/1/323
>
> There *are* some differences, and I'd like to inquire about
> them before I simply use the code you have for my purpose.
>
> These first two relate to whether I can use your
> code as-is:
> - Why do you skip setting the clock if a null "old"
> pointer is supplied?
> - I don't believe it's necessary to surround the clock
> rate change with clk_disable_unprepare() and
> clk_prepare_enable(). Do you believe otherwise?
>
> This one is addressed to how your code is used now:
> - Alan Cox had this question about my patch, and
> it seems to apply to your code as well:
> "This assumes an arbitarily configurable clock,
> which is not I think the usual case."
> https://lkml.org/lkml/2014/6/28/91
> His point is that the clock, if adjustable, may
> not support a rate that produces an acceptable
> signal rate. Put another way, there may be a
> better frequency than what the clock framework
> selects that (in combination with the UART
> divisor latch registers) produces the best--or
> even a good--signal. Is there any chance any
> ACPI platforms will suffer this problem?
>
> Thanks.
>
> -Alex
>



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