Re: [PATCH] drivers: char: omap-uart: add "clock-hz" option

[Amneesh Singh <a-singh21@xxxxxx>]

On 10:16-20240806, Julien Grall wrote:
> Hi,
> 
> On 19/07/2024 12:33, Amneesh Singh wrote:
> > Quite a few TI K3 devices do not have clock-frequency specified in their
> > respective UART nodes.
> 
> Can you outline why fixing the device-tree is not solution?
Because other frequencies, say 96MHz or 192 MHz are also valid inputs.
> 
> > However hard-coding the frequency is not a
>  > solution as the function clock input can differ between SoCs.
> 
> Can you provide some details how Linux is handling those SoCs?
Yes, like omap-uart under xen, the 8250_omap driver also parses the DT,
but unlike omap-uart, falls back to clk_get_rate() and if the value is
still zero, it defaults to 48MHz.
> 
> > So,
> > similar to com1/com2, let the user pass the frequency as a dtuart option
> > via the bootargs. If not specified it will fallback to the same DT
> > parsing as before. For example, dtuart=serial2:clock-hz=48000000 can be
> > a valid bootarg.
> 
> Regardless my questions, any change to the command line needs to be
> documented in docs/misc/xen-command-line.pandoc.
I am not sure if that will be necessary as the dtuart option already
says: "The options are device specific."
> 
> Cheers,
> 
> --
> Julien Grall
> 
> 
Regards
Amneesh