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SubjectRe: [PATCH] coresight: Defer probe when the child dev is not probed
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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,

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