2011-04-25 13:25:30

by Magnus Damm

Subject: [PATCH] clocksource: sh_cmt: __clocksource_updatefreq_hz() update

From: Magnus Damm <[email protected]>

This patch updates the clocksource part of the CMT driver
to make use of the __clocksource_updatefreq_hz() function.

Without this patch the old code uses clocksource_register()
together with a hack that assumes a never changing clock rate
(see clk_enable(), clk_get_rate() and clk_disable()).

The patch uses clocksource_register_hz() with 1 Hz as initial
value, then lets the ->enable() callback update the value
with __clocksource_updatefreq_hz() once the struct clk has
been enabled and the frequency is stable.

Signed-off-by: Magnus Damm <[email protected]>
---

Thanks to John Stultz for the framework changes and the
initial implementation.

Tested on the sh7372 Mackerel board with CMT10.

drivers/clocksource/sh_cmt.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)

--- 0001/drivers/clocksource/sh_cmt.c
+++ work/drivers/clocksource/sh_cmt.c 2011-04-25 14:47:06.000000000 +0900
@@ -416,11 +416,15 @@ static cycle_t sh_cmt_clocksource_read(s

static int sh_cmt_clocksource_enable(struct clocksource *cs)
{
+ int ret;
struct sh_cmt_priv *p = cs_to_sh_cmt(cs);

p->total_cycles = 0;

- return sh_cmt_start(p, FLAG_CLOCKSOURCE);
+ ret = sh_cmt_start(p, FLAG_CLOCKSOURCE);
+ if (!ret)
+ __clocksource_updatefreq_hz(cs, p->rate);
+ return ret;
}

static void sh_cmt_clocksource_disable(struct clocksource *cs)
@@ -448,19 +452,10 @@ static int sh_cmt_register_clocksource(s
cs->mask = CLOCKSOURCE_MASK(sizeof(unsigned long) * 8);
cs->flags = CLOCK_SOURCE_IS_CONTINUOUS;

- /* clk_get_rate() needs an enabled clock */
- clk_enable(p->clk);
- p->rate = clk_get_rate(p->clk) / ((p->width == 16) ? 512 : 8);
- clk_disable(p->clk);
-
- /* TODO: calculate good shift from rate and counter bit width */
- cs->shift = 0;
- cs->mult = clocksource_hz2mult(p->rate, cs->shift);
-
dev_info(&p->pdev->dev, "used as clock source\n");

- clocksource_register(cs);
-
+ /* Register with dummy 1 Hz value, gets updated in ->enable() */
+ clocksource_register_hz(cs, 1);
return 0;
}

2011-04-28 20:55:19

by john stultz

Subject: Re: [PATCH] clocksource: sh_cmt: __clocksource_updatefreq_hz() update

On Mon, 2011-04-25 at 22:32 +0900, Magnus Damm wrote:
> From: Magnus Damm <[email protected]>
>
> This patch updates the clocksource part of the CMT driver
> to make use of the __clocksource_updatefreq_hz() function.
>
> Without this patch the old code uses clocksource_register()
> together with a hack that assumes a never changing clock rate
> (see clk_enable(), clk_get_rate() and clk_disable()).
>
> The patch uses clocksource_register_hz() with 1 Hz as initial
> value, then lets the ->enable() callback update the value
> with __clocksource_updatefreq_hz() once the struct clk has
> been enabled and the frequency is stable.
>
> Signed-off-by: Magnus Damm <[email protected]>

Acked-by: John Stultz <[email protected]>

If these don't get picked up for 2.6.40, I'll queue them myself.

thanks
-john