clocksource/drivers/imx-tpm: Fix next event not taking effect sometime

The value written into the TPM CnV can only be updated into the hardware
when the counter increases. Additional writes to the CnV write buffer are
ignored until the register has been updated. Therefore, we need to check
if the CnV has been updated before continuing. This may require waiting for
1 counter cycle in the worst case.

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]>

diff --git a/drivers/clocksource/timer-imx-tpm.c b/drivers/clocksource/timer-imx-tpm.c
index cd23caf1e59995893fad70893b3e262293d84f2b..92c025b70eb62f5a03e9cf3aa9bf5e54f9e6c53a 100644 (file)
--- a/drivers/clocksource/timer-imx-tpm.c
+++ b/drivers/clocksource/timer-imx-tpm.c
@@ -90,6 +90,14 @@ static int tpm_set_next_event(unsigned long delta,
        writel(next, timer_base + TPM_C0V);
        now = tpm_read_counter();
 
+       /*
+        * Need to wait CNT increase at least 1 cycle to make sure
+        * the C0V has been updated into HW.
+        */
+       if ((next & 0xffffffff) != readl(timer_base + TPM_C0V))
+               while (now == tpm_read_counter())
+                       ;
+
        /*
         * NOTE: We observed in a very small probability, the bus fabric
         * contention between GPU and A7 may results a few cycles delay