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

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Message-ID: <b11d65db-d691-4f5d-b41a-db5b29a8ae01@linaro.org>
Date: Mon, 19 Aug 2024 11:16:16 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Bjorn Andersson <quic_bjorande@...cinc.com>,
 Sebastian Reichel <sre@...nel.org>, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konrad.dybcio@...aro.org>,
 Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Johan Hovold <johan+linaro@...nel.org>, Chris Lew
 <quic_clew@...cinc.com>, Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Stephen Boyd <swboyd@...omium.org>, Amit Pundir <amit.pundir@...aro.org>,
 linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH 2/3] usb: typec: ucsi: Move unregister out of atomic
 section

On 19/08/2024 01:17, Bjorn Andersson wrote:
> 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@...r.kernel.org
> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.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)
> 

Looks good, I'll run it on the 8550/8650 platforms

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>