Re: [PATCH 6/7] remoteproc: qcom_q6v5_pas: Add hwspinlock bust on stop

[Chris Lew]

On 5/21/2024 10:38 AM, Konrad Dybcio wrote:
> On 5/17/24 00:58, Chris Lew wrote:
> > From: Richard Maina <quic_rmaina@xxxxxxxxxxx>
> >
> > When remoteproc goes down unexpectedly this results in a state where any
> > acquired hwspinlocks will remain locked possibly resulting in deadlock.
> > In order to ensure all locks are freed we include a call to
> > hwspin_lock_bust() during remoteproc shutdown.
> >
> > For qcom_q6v5_pas remoteprocs, each remoteproc has an assigned id that
> > is used to take the hwspinlock. Remoteproc should use this id to try and
> > bust the lock on remoteproc stop.
> >
> > This edge case only occurs with q6v5_pas watchdog crashes. The error
> > fatal case has handling to clear the hwspinlock before the error fatal
> > interrupt is triggered.
> >
> > Signed-off-by: Richard Maina <quic_rmaina@xxxxxxxxxxx>
> > Signed-off-by: Chris Lew <quic_clew@xxxxxxxxxxx>
> > ---
>
>
> >   drivers/remoteproc/qcom_q6v5_pas.c | 28 ++++++++++++++++++++++++++++
> >   1 file changed, 28 insertions(+)
> >
> > diff --git a/drivers/remoteproc/qcom_q6v5_pas.c 
> > b/drivers/remoteproc/qcom_q6v5_pas.c
> > index 54d8005d40a3..57178fcb9aa3 100644
> > --- a/drivers/remoteproc/qcom_q6v5_pas.c
> > +++ b/drivers/remoteproc/qcom_q6v5_pas.c
> > @@ -10,6 +10,7 @@
> >   #include <linux/clk.h>
> >   #include <linux/delay.h>
> >   #include <linux/firmware.h>
> > +#include <linux/hwspinlock.h>
> >   #include <linux/interrupt.h>
> >   #include <linux/kernel.h>
> >   #include <linux/module.h>
> > @@ -52,6 +53,7 @@ struct adsp_data {
> >       const char *ssr_name;
> >       const char *sysmon_name;
> >       int ssctl_id;
> > +    int hwlock_id;
> >       int region_assign_idx;
> >       int region_assign_count;
> > @@ -84,6 +86,9 @@ struct qcom_adsp {
> >       bool decrypt_shutdown;
> >       const char *info_name;
> > +    struct hwspinlock *hwlock;
> > +    int hwlock_id;
>
> IIRC, this is the same one that is passed in the DT.
>
> Can we get it dynamically from there?

The argument passed in DT is the index of the hwlock in the TCSR mutex 
region. The index determines use of hwlock[0..n]

This id is supposed to be the identifier that is passed into 
hwspin_lock_bust(). The actual value that we would read from 
hwlock[0..n] to see if we need to bust the lock.

Maybe the naming of this variable is confusing. Do you have any 
suggestions to make it clearer? Could call it hwlock_bust_id.

We could also try increasing the #hwlock-cells to 2 and have something 
like <&phandle index bust_id>. To me this seemed odd for clients that 
weren't planning on using the bust_id.

> Konrad