Re: [PATCH] coresight-etm4x: add isb() before reading the TRCSTATR

[Suzuki K Poulose]

Hi


On 04/12/2024 10:13, yuanfang zhang wrote:
> From: Yuanfang Zhang <quic_yuanfang@xxxxxxxxxxx>
>
> As recommended by section 4.3.7 ("Synchronization when using system
> instructions to progrom the trace unit") of ARM IHI 0064H.b, the
> self-hosted trace analyzer must perform a Context synchronization
> event between writing to the TRCPRGCTLR and reading the TRCSTATR.

Thanks for the patch. Please could you add the above in a comment
in the changes below ?

Also, add Fixes tag ? (It may go all the way back to initial support)

Otherwise looks sensible to me.

Suzuki

> Signed-off-by: Yuanfang Zhang <quic_yuanfang@xxxxxxxxxxx>
> ---
>   drivers/hwtracing/coresight/coresight-etm4x-core.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 66d44a404ad0..5da2c523c30a 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -906,6 +906,7 @@ static void etm4_disable_hw(void *info)
>   	tsb_csync();
>   	etm4x_relaxed_write32(csa, control, TRCPRGCTLR);
>   
> +	isb();
>   	/* wait for TRCSTATR.PMSTABLE to go to '1' */
>   	if (coresight_timeout(csa, TRCSTATR, TRCSTATR_PMSTABLE_BIT, 1))
>   		dev_err(etm_dev,