linux-kernel - Re: [PATCH v17 09/12] PCI/AER: Allow clearing Error Status Register in FF mode

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Date:   Tue, 10 Mar 2020 20:49:29 +0000
From:   <Austin.Bolen@...l.com>
To:     <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        <Austin.Bolen@...l.com>, <helgaas@...nel.org>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <ashok.raj@...el.com>
Subject: Re: [PATCH v17 09/12] PCI/AER: Allow clearing Error Status Register
 in FF mode

On 3/10/2020 3:44 PM, Kuppuswamy Sathyanarayanan wrote:
> 
<snip>
> 
> Please check the following spec reference (change to 4.5.1 Table 4-6)
> 
> the OS is permitted to read or write DPC Control and Status registers of a
> port while processing an Error Disconnect Recover notification from firmware
> on that port. Error Disconnect Recover notification processing begins
> with the
> Error Disconnect Recover notify from Firmware, and *ends when the OS
> releases
> DPC by clearing the DPC Trigger Status bit*.Firmware can read DPC Trigger
> Status bit to determine the ownership of DPC Control and Status
> registers. Firmware
> is not permitted to write to DPC Control and Status registers if DPC
> Trigger Status is
> set i.e. the link is in DPC state. *Outside of the Error Disconnect
> Recover notification
> processing window, the OS is not permitted to modify DPC Control or
> Status registers*;
> only firmware is allowed to.
> 
> Since the EDR processing window ends with clearing DPC Trigger status
> bit, OS needs to
> clear DPC and AER registers before it ends.
> 
> Austin,
> 
> I think the order needs to be reversed in the implementation note.

Agreed.