Hi Guenter,

On 21 May 2015 at 23:28, Guenter Roeck [off-list ref] wrote:

On Thu, May 21, 2015 at 08:09:02AM -0500, Timur Tabi wrote:

quoted

Guenter Roeck wrote:

quoted

quoted

+static unsigned int sbsa_gwdt_get_timeleft(struct watchdog_device *wdd)
+{
+    struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
+    u64 timeleft = sbsa_gwdt_get_wcv(wdd) - arch_counter_get_cntvct();
+

Still not happy about the use of arch_counter_get_cntvct
instead of using the clock subsystem. I am quite sure this could be done,
possibly through arch_sys_counter, though at this point I am getting wary
of bringing it up, so I guess I'll just let it go.

You made the same comment with my driver, and I keep asking for
clarification.  The clk_get_sys() API does not work on my system, because
there are not clocks defined.  That must be an ACPI limitation that I can't
fix.

Would it be possible to define such clocks ?

quoted

The alternative to arch_counter_get_cntvct() is arch_timer_read_counter(),
which is not exported.  So we have two choices,

1) Continue to use arch_counter_get_cntvct(), which works on all ARM64
platforms that this driver supports anyway

2) Export arch_timer_read_counter()

I prefer option #1.

Do we have any feedback from the arm maintainers ?

My problem is that I don't want to be the first one to permit using
those functions outside architecture and clock code. If we do this,
we should get an Ack from an arm maintainer specifically for the use
of arch_counter_get_cntvct() and arch_timer_get_rate().

IMO, we may need to use  arch_timer_read_counter.
Reason:  Once the Linux kernel has KVM support and is in hyp mode. we
may need to use arch_counter_get_cntpct.
So arch_timer driver have helped us to make arch_timer_read_counter
point to the right function.
and arch_timer_read_counter is in the
include/clocksource/arm_arch_timer.h,  just like arch_timer_get_rate
as a interface

Thanks,
Guenter
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Best regards,

Fu Wei
Software Engineer
Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch
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