linux-kernel - Re: [RFC PATCH 1/9] PCI/AER: Update AER driver to call root port and downstream port UCE handlers

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Date: Fri, 21 Jun 2024 12:17:32 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Terry Bowman <terry.bowman@....com>, <dan.j.williams@...el.com>,
	<ira.weiny@...el.com>, <dave@...olabs.net>, <dave.jiang@...el.com>,
	<alison.schofield@...el.com>, <ming4.li@...el.com>,
	<vishal.l.verma@...el.com>, <jim.harris@...sung.com>,
	<ilpo.jarvinen@...ux.intel.com>, <ardb@...nel.org>,
	<sathyanarayanan.kuppuswamy@...ux.intel.com>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <Yazen.Ghannam@....com>,
	<Robert.Richter@....com>
CC: Bjorn Helgaas <bhelgaas@...gle.com>, <linux-pci@...r.kernel.org>
Subject: Re: [RFC PATCH 1/9] PCI/AER: Update AER driver to call root port and
 downstream port UCE handlers

Terry Bowman wrote:
> The AER service driver does not currently call a handler for AER
> uncorrectable errors (UCE) detected in root ports or downstream
> ports. This is not needed in most cases because common PCIe port
> functionality is handled by portdrv service drivers.
> 
> CXL root ports include CXL specific RAS registers that need logging
> before starting do_recovery() in the UCE case.
> 
> Update the AER service driver to call the UCE handler for root ports
> and downstream ports. These PCIe port devices are bound to the portdrv
> driver that includes a CE and UCE handler to be called.
> 
> Signed-off-by: Terry Bowman <terry.bowman@....com>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: linux-pci@...r.kernel.org
> ---
>  drivers/pci/pcie/err.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> index 705893b5f7b0..a4db474b2be5 100644
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -203,6 +203,26 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>  	pci_ers_result_t status = PCI_ERS_RESULT_CAN_RECOVER;
>  	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
>  
> +	/*
> +	 * PCIe ports may include functionality beyond the standard
> +	 * extended port capabilities. This may present a need to log and
> +	 * handle errors not addressed in this driver. Examples are CXL
> +	 * root ports and CXL downstream switch ports using AER UIE to
> +	 * indicate CXL UCE RAS protocol errors.
> +	 */
> +	if (type == PCI_EXP_TYPE_ROOT_PORT ||
> +	    type == PCI_EXP_TYPE_DOWNSTREAM) {
> +		struct pci_driver *pdrv = dev->driver;
> +
> +		if (pdrv && pdrv->err_handler &&
> +		    pdrv->err_handler->error_detected) {
> +			const struct pci_error_handlers *err_handler;
> +
> +			err_handler = pdrv->err_handler;
> +			status = err_handler->error_detected(dev, state);
> +		}
> +	}
> +

Would not a more appropriate place for this be pci_walk_bridge() where
the ->subordinate == NULL and these type-check cases are unified?