Re: [PATCH] coresight: etm4x: Skip setting LPOVERRIDE bit for qcom,skip-power-up

[Suzuki Poulose]

Hi Sai,

On 10/16/20 11:10 AM, Sai Prakash Ranjan wrote:

There is a bug on the systems supporting to skip power up
(qcom,skip-power-up) where setting LPOVERRIDE bit(low-power
state override behaviour) will result in CPU hangs/lockups
even on the implementations which supports it. So skip
setting the LPOVERRIDE bit for such platforms.

Fixes: 02510a5aa78d ("coresight: etm4x: Add support to skip trace unit power 
up")
Signed-off-by: Sai Prakash Ranjan <saiprakash.ran...@codeaurora.org>

The fix is fine by me. Btw, is there a hardware Erratum assigned for
this ? It would be good to have the Erratum documented somewhere,
preferrably ( Documentation/arm64/silicon-errata.rst )

---
  drivers/hwtracing/coresight/coresight-etm4x-core.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c 
b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index abd706b216ac..6096d7abf80d 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -779,7 +779,7 @@ static void etm4_init_arch_data(void *info)
         * LPOVERRIDE, bit[23] implementation supports
         * low-power state override
         */
-       if (BMVAL(etmidr5, 23, 23))
+       if (BMVAL(etmidr5, 23, 23) && (!drvdata->skip_power_up))
                drvdata->lpoverride = true;
        else
                drvdata->lpoverride = false;

base-commit: 3477326277451000bc667dfcc4fd0774c039184c