Re: [PATCH 3/5] cxl/pci: Discover and cache pointer to RCD dport's CXL RAS registers

[Terry Bowman]

Hi Ariel,


On 10/28/22 07:53, Ariel.Sibley@xxxxxxxxxxxxx wrote:
>> -----Original Message-----
>> From: Terry Bowman <terry.bowman@xxxxxxx>
>> Sent: Friday, October 21, 2022 3:56 PM
>> To: alison.schofield@xxxxxxxxx; vishal.l.verma@xxxxxxxxx; dave.jiang@xxxxxxxxx; ira.weiny@xxxxxxxxx;
>> bwidawsk@xxxxxxxxxx; dan.j.williams@xxxxxxxxx
>> Cc: terry.bowman@xxxxxxx; linux-cxl@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx;
>> rafael@xxxxxxxxxx; lenb@xxxxxxxxxx; Jonathan.Cameron@xxxxxxxxxx; dave@xxxxxxxxxxxx; rrichter@xxxxxxx
>> Subject: [PATCH 3/5] cxl/pci: Discover and cache pointer to RCD dport's CXL RAS registers
>>
>> CXL RAS information resides in a RAS capability structure located in
>> CXL.cache and CXL.mem registers.[1] The RAS capability provides CXL
>> specific error information that can be helpful in debugging. This
>> information is not currently logged but needs to be logged during PCIe AER
>> error handling.
>>
>> Update the CXL driver to find and cache a pointer to the CXL RAS
>> capability. The RAS registers resides in the downport's component register
>> block. Note:RAS registers are not in the upport. The component registers
>> can be found by first using the RCRB to goto the downport. Next, the
>> downport's 64-bit BAR[0] will point to the component register block.
> 
> I realize this patch is for dport only, but regarding "Note:RAS registers
> are not in the upport.", the upstream port also has RAS registers.
> 

Correct. Thanks for pointing this out.

> Per CXL 3.0 Section 12.2.1.2 RCD Upstream Port-detected Errors:
> "1. If a CXL.cache or CXL.mem logic block in UPZ detects a protocol or link
> error, the block shall log the error in the CXL RAS Capability (see Section
> 8.2.4.16)."