Re: [PATCH v02] mailbox: pcc: report errors for PCC clients

[Adam Young]

On 6/3/26 11:15, Adam Young wrote:
> On 5/19/26 09:23, Sudeep Holla wrote:
> > On Mon, May 18, 2026 at 03:30:06PM -0400, Adam Young wrote:
> > > The tx_done callback function has a return code (rc) parameter
> > > that the tx_done callback can use to determine how to handle an error.
> > > However the IRQ handler was not setting that value if there is an 
> > > error.
> > >
> > > The following clients are affected:
> > >
> > > drivers/acpi/cppc_acpi.c
> > > drivers/i2c/busses/i2c-xgene-slimpro.c
> > > drivers/hwmon/xgene-hwmon.c
> > > drivers/soc/hisilicon/kunpeng_hccs.c
> > > drivers/devfreq/hisi_uncore_freq.c
> > >
> > > All of these only use the error code to report, so they
> > > are expecting an error code to come thorugh, but they
> > > do not modify behavior based on this code.
> > >
> > > In the case of an error code in the IRQ, the handler was returning
> > > IRQ_NONE which is not correct:  the IRQ handler was matched
> > > to the IRQ.  This mean that multiple error codes returned from
> > > a PCC triggered interrupt would end up disabling the device.
> > >
> > > In addition, if the error code IRQ was coming from a Type4 Device 
> > > that was
> > > expecting an IRQ response, that device would then be hung.
> > >
> > > Fixes: c45ded7e1135 ("mailbox: pcc: Add support for PCCT extended 
> > > PCC subspaces(type 3/4)")
> > > Signed-off-by: Adam Young <admiyo@xxxxxxxxxxxxxxxxxxxxxx>
> > >
> > > ---
> > > ---
> > >   drivers/mailbox/pcc.c | 9 +++++----
> > >   1 file changed, 5 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> > > index 636879ae1db7..16b9ce087b9e 100644
> > > --- a/drivers/mailbox/pcc.c
> > > +++ b/drivers/mailbox/pcc.c
> > > @@ -314,6 +314,7 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
> > >   {
> > >       struct pcc_chan_info *pchan;
> > >       struct mbox_chan *chan = p;
> > > +    int rc;
> > >         pchan = chan->con_priv;
> > >   @@ -327,8 +328,7 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
> > >       if (!pcc_mbox_cmd_complete_check(pchan))
> > >           return IRQ_NONE;
> > >   -    if (pcc_mbox_error_check_and_clear(pchan))
> > > -        return IRQ_NONE;
> > > +    rc = pcc_mbox_error_check_and_clear(pchan);
> > I think we may have to skip the check inside 
> > pcc_mbox_error_check_and_clear()
> > for Type 4 channel as the spec expects OSPM to ignore it. It is a 
> > separate
> > fix, just noting that here.
>
> I think that should be in this patch, for correctness.  It is a small 
> enough change.  I'll update.

Actually, it is a fix in its own right, and can be merged regardless of 
this patch, so:
https://lore.kernel.org/lkml/20260604163306.160017-1-admiyo@xxxxxxxxxxxxxxxxxxxxxx/