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Date: Thu, 21 Jun 2018 08:05:25 -0600
From: Keith Busch <keith.busch@intel.com>
To: poza@codeaurora.org
Cc: Linux PCI <linux-pci@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Sinan Kaya <okaya@codeaurora.org>
Subject: Re: [PATCH 5/7] PCI/DPC: Print AER status in DPC event handling
Message-ID: <20180621140525.GB26623@localhost.localdomain>
References: <20180620213833.25072-1-keith.busch@intel.com>
 <20180620213833.25072-5-keith.busch@intel.com>
 <9cc1594055f03c0e4b4d1b50384107e8@codeaurora.org>
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On Thu, Jun 21, 2018 at 02:46:10PM +0530, poza@codeaurora.org wrote:
> On 2018-06-21 03:08, Keith Busch wrote:
> > @@ -185,6 +187,10 @@ static void dpc_work(struct work_struct *work)
> >  	/* show RP PIO error detail information */
> >  	if (dpc->rp_extensions && reason == 3 && ext_reason == 0)
> >  		dpc_process_rp_pio_error(dpc);
> > +	else if (reason == 0 && aer_get_device_error_info(pdev, &info)) {
> > +		aer_print_error(pdev, &info);
> > +		pci_cleanup_aer_uncorrect_error_status(pdev);
> 
> 6.2.10 for Downstream Port Containment:
> 
>   When DPC is triggered due to receipt of an uncorrectable error Message,
>   the Requester ID from the Message is recorded in the DPC Error
>   Source ID register and that Message is discarded and not forwarded
>   Upstream. When DPC is triggered by an unmasked uncorrectable error,
>   that error will not be signaled with an uncorrectable error Message,
>   even if otherwise enabled.
> 
> Inst the message is discarded and not forwarded to upstream.
> which means that we should not find AER status set in RP or Switch.
> in other words, at time either we will find DPC or AER triggered but not
> both at the same time.
> then when DPC is triggered why do we need to
> pci_cleanup_aer_uncorrect_error_status(pdev); ?

According to the sequence diagram in 6.2.5, an uncorrectable error has
the cooresponding bits set in the Device Status and AER Uncorrectable
Error Status registers before DPC specifics are considered. DPC just
suppresses the ERR_[NON]FATAL messages, but the detecting ports AER
status, if implemented, should reflect what occured.