Hi Jinlong

On 28/02/2022 13:31, Mao Jinlong wrote:

From: Mao Jinlong jinlmao@qti.qualcomm.com

It is possible that when device probe, its child device is not probed. Then it will fail when add sysfs connection for the device. Make device defer probe when the child device is not probed.

Please could you a bit a more specific on the exact issue ? I don't see a problem with probe deferral right now, with coresight/next.

For e.g.,

root@juno-server:~# lsmod Module Size Used by coresight 73728 0 root@juno-server:~# ls /sys/bus/coresight/devices/ root@juno-server:~# modprobe coresight-etm4x root@juno-server:~# lsmod Module Size Used by coresight_etm4x 81920 0 coresight 73728 1 coresight_etm4x root@juno-server:~# ls /sys/bus/coresight/devices/ etm0 etm1

-- Note etm2-etm5 doesn't appear --

root@juno-server:~# modprobe coresight-funnel root@juno-server:~# lsmod Module Size Used by coresight_funnel 20480 0 coresight_etm4x 81920 0 coresight 73728 2 coresight_etm4x,coresight_funnel root@juno-server:~# ls /sys/bus/coresight/devices/ etm0 etm1

-- Still don't appear ---

root@juno-server:~# modprobe coresight-replicator root@juno-server:~# ls /sys/bus/coresight/devices/ etm0 etm1 root@juno-server:~# modprobe coresight-tmc

-- At this stage, the devices automatically get probed and appear -- root@juno-server:~# ls /sys/bus/coresight/devices/ etm0 etm1 etm2 etm3 etm4 etm5 funnel0 funnel1 funnel2 tmc_etf0 tmc_etr0

root@juno-server:~# lsmod Module Size Used by coresight_tmc 40960 0 coresight_replicator 20480 0 coresight_funnel 20480 0 coresight_etm4x 81920 0 coresight 73728 4 coresight_tmc,coresight_etm4x,coresight_replicator,coresight_funnel

So, my question is, what is this patch trying to solve ?

Cheers Suzuki

Signed-off-by: Mao Jinlong jinlmao@qti.qualcomm.com

drivers/hwtracing/coresight/coresight-sysfs.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c index 34d2a2d31d00..7df9eb59bf2c 100644 --- a/drivers/hwtracing/coresight/coresight-sysfs.c +++ b/drivers/hwtracing/coresight/coresight-sysfs.c @@ -73,8 +73,10 @@ int coresight_add_sysfs_link(struct coresight_sysfs_link *info) if (!info->orig || !info->target || !info->orig_name || !info->target_name) return -EINVAL;

• if (!info->orig->has_conns_grp || !info->target->has_conns_grp)

• if (!info->orig->has_conns_grp) return -EINVAL;
• if (!info->target->has_conns_grp)

• return -EPROBE_DEFER;
  

/* first link orig->target */ ret = sysfs_add_link_to_group(&info->orig->dev.kobj,