clocksource/drivers/imx-tpm: Fix return -ETIME when delta exceeds INT_MAX

In tpm_set_next_event(delta), return -ETIME by wrong cast to int when delta
is larger than INT_MAX.

For example:

tpm_set_next_event(delta = 0xffff_fffe)
{
        ...
        next = tpm_read_counter(); // assume next is 0x10
        next += delta; // next will 0xffff_fffe + 0x10 = 0x1_0000_000e
        now = tpm_read_counter();  // now is 0x10
        ...

        return (int)(next - now) <= 0 ? -ETIME : 0;
                     ^^^^^^^^^^
                     0x1_0000_000e - 0x10 = 0xffff_fffe, which is -2 when
                     cast to int. So return -ETIME.
}

To fix this, introduce a 'prev' variable and check if 'now - prev' is
larger than delta.

Cc: [email protected]
Fixes: 059ab7b82eec ("clocksource/drivers/imx-tpm: Add imx tpm timer support")
Signed-off-by: Jacky Bai <[email protected]>
Reviewed-by: Peng Fan <[email protected]>
Reviewed-by: Ye Li <[email protected]>
Reviewed-by: Jason Liu <[email protected]>
Signed-off-by: Frank Li <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Daniel Lezcano <[email protected]>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/clocksource/timer-imx-tpm.c b/drivers/clocksource/timer-imx-tpm.c
index bd64a8a8427f..cd23caf1e599 100644
--- a/drivers/clocksource/timer-imx-tpm.c
+++ b/drivers/clocksource/timer-imx-tpm.c
@@ -83,10 +83,10 @@ static u64 notrace tpm_read_sched_clock(void)
 static int tpm_set_next_event(unsigned long delta,
 				struct clock_event_device *evt)
 {
-	unsigned long next, now;
+	unsigned long next, prev, now;
 
-	next = tpm_read_counter();
-	next += delta;
+	prev = tpm_read_counter();
+	next = prev + delta;
 	writel(next, timer_base + TPM_C0V);
 	now = tpm_read_counter();
 
@@ -96,7 +96,7 @@ static int tpm_set_next_event(unsigned long delta,
 	 * of writing CNT registers which may cause the min_delta event got
 	 * missed, so we need add a ETIME check here in case it happened.
 	 */
-	return (int)(next - now) <= 0 ? -ETIME : 0;
+	return (now - prev) >= delta ? -ETIME : 0;
 }
 
 static int tpm_set_state_oneshot(struct clock_event_device *evt)