From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@linaro.org>
Subject: Re: [PATCH v2 2/3] xen/arm: Add new driver for R-Car
	Gen2 UART
Date: Thu, 22 Jan 2015 17:02:52 +0000
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To: Oleksandr Tyshchenko <oleksandr.tyshchenko@globallogic.com>
Cc: Iurii Konovalenko <iurii.konovalenko@globallogic.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Tim Deegan <tim@xen.org>, Ian Campbell <ian.campbell@citrix.com>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
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On 22/01/15 16:55, Oleksandr Tyshchenko wrote:
> On Thu, Jan 22, 2015 at 6:49 PM, Julien Grall <julien.grall@linaro.org> 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