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

[Adam Young <admiyo@amperemail.onmicrosoft.com>]

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@os.amperecomputing.com>
>>>
>>> ---
>>> ---
>>>   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@os.amperecomputing.com/