On Mon, Jan 22, 2018 at 11:00:15AM +0200, Claudiu Beznea wrote:

On 17.01.2018 23:47, Ladislav Michl wrote:

quoted

Invalid value silently disables use of the prescaler.
Use -1 explicitely for that purpose and error out on
invalid value.

Signed-off-by: Ladislav Michl <redacted>
---
 drivers/clocksource/timer-dm.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/clocksource/timer-dm.c b/drivers/clocksource/timer-dm.c
index 60db1734ea3b..324ec93d3dd2 100644
--- a/drivers/clocksource/timer-dm.c
+++ b/drivers/clocksource/timer-dm.c

@@ -663,13 +663,13 @@ int omap_dm_timer_set_prescaler(struct omap_dm_timer *timer, int prescaler)
 {
 	u32 l;
 
-	if (unlikely(!timer))
+	if (unlikely(!timer) || prescaler < -1 || prescaler > 7)

You are checking the prescaller here to be in [0, 7] interval.

You mean [-1, 7] I suppose.

quoted

 		return -EINVAL;
 
 	omap_dm_timer_enable(timer);
 	l = omap_dm_timer_read_reg(timer, OMAP_TIMER_CTRL_REG);
 	l &= ~(OMAP_TIMER_CTRL_PRE | (0x07 << 2));
-	if (prescaler >= 0x00 && prescaler <= 0x07) {
+	if (prescaler >= 0) {

Is this check still necessary?

Yes, as we need also some way to disable prescaler, see commit message.

quoted

 		l |= OMAP_TIMER_CTRL_PRE;
 		l |= prescaler << 2;
 	}

Best regards,
	ladis