[PATCH 2/3] usb: typec: ucsi: Move unregister out of atomic section

Bjorn Andersson
2024-08-18T23:17:57Z

Commit 'caa855189104 ("soc: qcom: pmic_glink: Fix race during
initialization")' 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 IRQ 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, but it becomes expecting to see a failing send
upon shutting down the remote processor (e.g. during a restart following
a firmware crash):

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

Fixes: caa855189104 ("soc: qcom: pmic_glink: Fix race during initialization")
Cc: stable@vger.kernel.org
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
---
drivers/soc/qcom/pmic_glink.c | 10 +++++++++-
drivers/usb/typec/ucsi/ucsi_glink.c | 28 +++++++++++++++++++++++-----
2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/drivers/soc/qcom/pmic_glink.c b/drivers/soc/qcom/pmic_glink.c
index 58ec91767d79..e4747f1d3da5 100644
--- a/drivers/soc/qcom/pmic_glink.c
+++ b/drivers/soc/qcom/pmic_glink.c
@@ -112,8 +112,16 @@ EXPORT_SYMBOL_GPL(pmic_glink_register_client);
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);

diff --git a/drivers/usb/typec/ucsi/ucsi_glink.c b/drivers/usb/typec/ucsi/ucsi_glink.c
index ac53a81c2a81..a33056eec83d 100644
--- a/drivers/usb/typec/ucsi/ucsi_glink.c
+++ b/drivers/usb/typec/ucsi/ucsi_glink.c
@@ -68,6 +68,9 @@ struct pmic_glink_ucsi {

struct work_struct notify_work;
struct work_struct register_work;
+ spinlock_t state_lock;
+ unsigned int pdr_state;
+ unsigned int new_pdr_state;

u8 read_buf[UCSI_BUF_SIZE];
};
@@ -244,8 +247,22 @@ static void pmic_glink_ucsi_notify(struct work_struct *work)
static void pmic_glink_ucsi_register(struct work_struct *work)
{
struct pmic_glink_ucsi *ucsi = container_of(work, struct pmic_glink_ucsi, register_work);
+ unsigned long flags;
+ unsigned int new_state;
+
+ spin_lock_irqsave(&ucsi->state_lock, flags);
+ new_state = ucsi->new_pdr_state;
+ spin_unlock_irqrestore(&ucsi->state_lock, flags);
+
+ if (ucsi->pdr_state != SERVREG_SERVICE_STATE_UP) {
+ if (new_state == SERVREG_SERVICE_STATE_UP)
+ ucsi_register(ucsi->ucsi);
+ } else {
+ if (new_state == SERVREG_SERVICE_STATE_DOWN)
+ ucsi_unregister(ucsi->ucsi);
+ }

- ucsi_register(ucsi->ucsi);
+ ucsi->pdr_state = new_state;
}

static void pmic_glink_ucsi_callback(const void *data, size_t len, void *priv)
@@ -269,11 +286,12 @@ static void pmic_glink_ucsi_callback(const void *data, size_t len, void *priv)
static void pmic_glink_ucsi_pdr_notify(void *priv, int state)
{
struct pmic_glink_ucsi *ucsi = priv;
+ unsigned long flags;

- if (state == SERVREG_SERVICE_STATE_UP)
- schedule_work(&ucsi->register_work);
- else if (state == SERVREG_SERVICE_STATE_DOWN)
- ucsi_unregister(ucsi->ucsi);
+ spin_lock_irqsave(&ucsi->state_lock, flags);
+ ucsi->new_pdr_state = state;
+ spin_unlock_irqrestore(&ucsi->state_lock, flags);
+ schedule_work(&ucsi->register_work);
}

static void pmic_glink_ucsi_destroy(void *data)

--
2.34.1