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Re: [Xen-devel] [PATCH v2 2/3] xen/arm: Add new driver for R-Car Gen2 UART

On Thu, Jan 22, 2015 at 7:02 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> On 22/01/15 16:55, Oleksandr Tyshchenko wrote:
>> On Thu, Jan 22, 2015 at 6:49 PM, Julien Grall <julien.grall@xxxxxxxxxx> 
>> wrote:
>>> On 22/01/15 16:44, Oleksandr Tyshchenko wrote:
>>>> I understand, then I will implement local delay func in uart driver
>>>> based on READ_SYSREG64(CNTPCT_EL0).
>>> Unless I miss something, udelay should work in your case even if the
>>> xen_init_time is not called.
>> Unfortunately, no. If I understand correctly the var "cpu_khz" (used
>> in ticks_to_ns()) is initialized in init_xen_time().
> Hrm, right. I looked too quickly to the function.
> I don't like the idea to use READ_SYSREG64(CNTPCT_EL0) in the UART drivers.
> Does the udelay necessary here? If yes, maybe we should either split the
> xen_init_time in 2 parts or create a udelay_tick function to use when
> timer is not set.
> I'm not sure what is the best one.
> Regards,
> --
> Julien Grall

According to the TRM for this family we need to add delay after
changing baudrate before continuing init sequence.
I tried without udelay and it is worked fine. But, if the TRM says we
need to follow this.


Oleksandr Tyshchenko | Embedded Dev

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