[PATCH v2 1/7] spi: spi-mem: Add support for panic mem writes

[Paul Cercueil]

Hi Miquèl,

Le mardi 13 octobre 2026 à 17:57 +0200, Miquel Raynal a écrit :
> Hi Paul,
> 
> On 13/10/2026 at 17:33:32 +02, Paul Cercueil <paul.cercueil at bootlin.com>
> wrote:
> 
> > Hi Sashiko,
> 
> :-)
> 
> > > > -		ret = spi_mem_access_start(mem);
> > > > +		if (!op->panic_write)
> > > > +			ret = spi_mem_access_start(mem);
> > > > +		else if (ctlr->auto_runtime_pm)
> > > > +			ret = pm_runtime_get_if_active(ctlr-
> > > > >dev.parent);
> > > >  		if (ret)
> > > >  			return ret;
> > > 
> > > [Severity: High]
> > > Is it safe to call pm_runtime_get_if_active() here during a kernel panic?
> > > 
> > > pm_runtime_get_if_active() relies on pm_runtime_get_conditional(), which
> > > unconditionally acquires dev->power.lock via spin_lock_irqsave(). In a
> > > panic
> > > context with NMIs or IRQs disabled, trying to acquire a spinlock that may
> > > be
> > > held by a halted CPU causes an infinite spin. On PREEMPT_RT,
> > > spin_lock_irqsave()
> > > maps to a sleeping rt_mutex, which is strictly forbidden in atomic
> > > context.
> > 
> > ACK, I'll just drop pm_runtime_get_if_active() here, and restore the return
> > -
> > EOPNOTSUPP that was in v1 when ctlr->auto_runtime_pm is set.
> 
> This is tricky but automatically rules out about 1/6th of the
> controllers (45 controllers set this boolean out of +300). I don't like
> it much. I guess it deserves a comment in case someone ever wants to
> enable this feature on their auto-RPM-enabled controller, to understand
> why this is not possible. My gut feeling is that the runtime PM layer
> lacks its own understanding of what a panic is. We should, I believe, be
> able to query the usage_count of a controller without taking the lock
> during a panic write.
> 
> Nevertheless, let's move forward and return an error for now.

I guess I can use pm_runtime_active() then?

Cheers,
-Paul