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.

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,
-- 
2.17.1

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,