linux-kernel - Re: [PATCH v10 09/17] cxl/pci: Map CXL Endpoint Port and CXL Switch Port RAS registers

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Message-ID: <2c747d35-6793-4f0c-9351-a5be1ba44e7b@amd.com>
Date: Wed, 2 Jul 2025 16:41:20 -0500
From: "Bowman, Terry" <terry.bowman@....com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: dave@...olabs.net, dave.jiang@...el.com, alison.schofield@...el.com,
 dan.j.williams@...el.com, bhelgaas@...gle.com, shiju.jose@...wei.com,
 ming.li@...omail.com, Smita.KoralahalliChannabasappa@....com,
 rrichter@....com, dan.carpenter@...aro.org,
 PradeepVineshReddy.Kodamati@....com, lukas@...ner.de,
 Benjamin.Cheatham@....com, sathyanarayanan.kuppuswamy@...ux.intel.com,
 linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-pci@...r.kernel.org
Subject: Re: [PATCH v10 09/17] cxl/pci: Map CXL Endpoint Port and CXL Switch
 Port RAS registers



On 6/27/2025 6:17 AM, Jonathan Cameron wrote:
> On Thu, 26 Jun 2025 17:42:44 -0500
> Terry Bowman <terry.bowman@....com> wrote:
>
>> CXL Endpoint (EP) Ports may include Root Ports (RP) or Downstream Switch
>> Ports (DSP). CXL RPs and DSPs contain RAS registers that require memory
>> mapping to enable RAS logging. This initialization is currently missing and
>> must be added for CXL RPs and DSPs.
>>
>> Update cxl_dport_init_ras_reporting() to support RP and DSP RAS mapping.
>> Add alongside the existing Restricted CXL Host Downstream Port RAS mapping.
>>
>> Update cxl_endpoint_port_probe() to invoke cxl_dport_init_ras_reporting().
>> This will initiate the RAS mapping for CXL RPs and DSPs when each CXL EP is
>> created and added to the EP port.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@....com>
> One trivial comment inline.  I'm not super confident that I follow exactly
> what is going on here so more eyes needed.  However I think it's fine.
>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>

Thanks.
>> diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
>> index 021f35145c65..b52f82925891 100644
>> --- a/drivers/cxl/port.c
>> +++ b/drivers/cxl/port.c
>>  
>> +static void cxl_switch_port_init_ras(struct cxl_port *port)
>> +{
>> +	if (is_cxl_root(to_cxl_port(port->dev.parent)))
>> +		return;
>> +
>> +	/* May have upstream DSP or RP */
>> +	if (port->parent_dport && dev_is_pci(port->parent_dport->dport_dev)) {
>  A lot of port->parent_dport in here. Maybe a local variable for that with
> a suitable name to describe that its the next port in the upstream direction.
Ok, I'll add a local pointer to make it more readable.

-Terry
>> +		struct pci_dev *pdev = to_pci_dev(port->parent_dport->dport_dev);
>> +
>> +		if ((pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT) ||
>> +		    (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM))
>> +			cxl_dport_init_ras_reporting(port->parent_dport, &port->dev);
>> +	}
>> +
>> +	cxl_uport_init_ras_reporting(port, &port->dev);
>> +}
>> +
>> +static void cxl_endpoint_port_init_ras(struct cxl_port *port)
>> +{
>> +	struct cxl_dport *dport;
>> +	struct cxl_memdev *cxlmd = to_cxl_memdev(port->uport_dev);
>> +	struct cxl_port *parent_port __free(put_cxl_port) =
>> +		cxl_mem_find_port(cxlmd, &dport);
>> +
>> +	if (!dport || !dev_is_pci(dport->dport_dev)) {
>> +		dev_err(&port->dev, "CXL port topology not found\n");
>> +		return;
>> +	}
>> +
>> +	cxl_dport_init_ras_reporting(dport, cxlmd->cxlds->dev);
>> +}
>>