[U-Boot] [PATCH v5 3/9] arm: add support for arch timer

[FengHua]

> -----Original Messages-----
> From: "Andrianov, Vitaly" <vitalya at ti.com>
> Sent Time: 2014-04-03 19:22:34 (Thursday)
> To: "Masahiro Yamada" <yamada.m at jp.panasonic.com>, "Karicheri, Muralidharan" <m-karicheri2 at ti.com>
> Cc: "Rini, Tom" <trini at ti.com>, "u-boot at lists.denx.de" <u-boot at lists.denx.de>
> Subject: Re: [U-Boot] [PATCH v5 3/9] arm: add support for arch timer
> 
> Hi Masahiro,
> 
> > -----Original Message-----
> > From: u-boot-bounces at lists.denx.de [mailto:u-boot-
> > bounces at lists.denx.de] On Behalf Of Masahiro Yamada
> > Sent: Wednesday, April 02, 2014 9:46 PM
> > To: Karicheri, Muralidharan
> > Cc: Rini, Tom; u-boot at lists.denx.de
> > Subject: Re: [U-Boot] [PATCH v5 3/9] arm: add support for arch timer
> > 
> > Hi Murali,
> > 
> > On Tue, 1 Apr 2014 14:44:23 -0400
> > Murali Karicheri <m-karicheri2 at ti.com> wrote:
> > 
> > > From: Vitaly Andrianov <vitalya at ti.com>
> > >
> > > This patch add basic support for the architecture timer found on
> > > recent
> > > ARMv7 based SoCs.
> > >
> > > Signed-off-by: Vitaly Andrianov <vitalya at ti.com>
> > > Signed-off-by: Murali Karicheri <m-karicheri2 at ti.com>
> > > Acked-by: Tom Rini <trini at ti.com>
> > > ---
> > >  arch/arm/lib/Makefile     |    1 +
> > >  arch/arm/lib/arch_timer.c |   58
> > +++++++++++++++++++++++++++++++++++++++++++++
> > 
> > 
> > 
> > I am not familiar with this timer, but your commit description implies
> > it is specific to ARMv7.
> > 
> > If so, it looks like it should go to arch/arm/cpu/armv7/ .
> > Is this right?
> 
> This is for arch timer implemented in ARM Cortex-A15 which is ARMv7.
> I believe the same arch timer is in ARMv8. So, it is not specific to
> ARMv7 only. The commit description mentioned only ARMv7 because the
> driver was designed and tested on ARMv7.    
> 
If we want to apply the arch_timer.c to armv8,  the get_ticks() function should be modified
due to mrrc instuction. 
Furthermore, armv8 now make use of timer infrastructure of lib/time.c. 
Only get_tbclk() and timer_read_counter() are architecture specific and declared in generic_timer.c.
We'd better construct a common arch timer structure across arm platform.

Best regards,
David