usb: typec: ucsi: Move unregister out of atomic section

Commit '9329933699b3 ("soc: qcom: pmic_glink: Make client-lock
non-sleeping")' moved the pmic_glink client list under a spinlock, as it
is accessed by the rpmsg/glink callback, which in turn is invoked from
IRQ context.

This means that ucsi_unregister() is now called from atomic context,
which isn't feasible as it's expecting a sleepable context. An effort is
under way to get GLINK to invoke its callbacks in a sleepable context,
but until then lets schedule the unregistration.

A side effect of this is that ucsi_unregister() can now happen
after the remote processor, and thereby the communication link with it, is
gone. pmic_glink_send() is amended with a check to avoid the resulting NULL
pointer dereference.
This does however result in the user being informed about this error by
the following entry in the kernel log:

  ucsi_glink.pmic_glink_ucsi pmic_glink.ucsi.0: failed to send UCSI write request: -5

Fixes: 9329933699b3 ("soc: qcom: pmic_glink: Make client-lock non-sleeping")
Cc: stable@vger.kernel.org
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: Amit Pundir <amit.pundir@linaro.org>
Reviewed-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Link: https://lore.kernel.org/r/20240820-pmic-glink-v6-11-races-v3-2-eec53c750a04@quicinc.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/drivers/soc/qcom/pmic_glink.c b/drivers/soc/qcom/pmic_glink.c
index 53b176d04fbd..b218460219b7 100644
--- a/drivers/soc/qcom/pmic_glink.c
+++ b/drivers/soc/qcom/pmic_glink.c
@@ -112,8 +112,16 @@ EXPORT_SYMBOL_GPL(pmic_glink_client_register);
 int pmic_glink_send(struct pmic_glink_client *client, void *data, size_t len)
 {
 	struct pmic_glink *pg = client->pg;
+	int ret;
 
-	return rpmsg_send(pg->ept, data, len);
+	mutex_lock(&pg->state_lock);
+	if (!pg->ept)
+		ret = -ECONNRESET;
+	else
+		ret = rpmsg_send(pg->ept, data, len);
+	mutex_unlock(&pg->state_lock);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(pmic_glink_send);