netdev - Re: [PATCH v9 06/27] cxl: add function for type2 cxl regs setup

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Message-ID: <678b092428a86_20fa29462@dwillia2-xfh.jf.intel.com.notmuch>
Date: Fri, 17 Jan 2025 17:51:32 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: <alejandro.lucero-palau@....com>, <linux-cxl@...r.kernel.org>,
	<netdev@...r.kernel.org>, <dan.j.williams@...el.com>, <edward.cree@....com>,
	<davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<edumazet@...gle.com>, <dave.jiang@...el.com>
CC: Alejandro Lucero <alucerop@....com>
Subject: Re: [PATCH v9 06/27] cxl: add function for type2 cxl regs setup

alejandro.lucero-palau@ wrote:
> From: Alejandro Lucero <alucerop@....com>
> 
> Create a new function for a type2 device initialising
> cxl_dev_state struct regarding cxl regs setup and mapping.
> 
> Signed-off-by: Alejandro Lucero <alucerop@....com>
> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> Reviewed-by: Fan Ni <fan.ni@...sung.com>
> ---
>  drivers/cxl/core/pci.c | 51 ++++++++++++++++++++++++++++++++++++++++++
>  include/cxl/cxl.h      |  2 ++
>  2 files changed, 53 insertions(+)
> 
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index 5821d582c520..493ab33fe771 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -1107,6 +1107,57 @@ int cxl_pci_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
>  }
>  EXPORT_SYMBOL_NS_GPL(cxl_pci_setup_regs, "CXL");
>  
> +static int cxl_pci_setup_memdev_regs(struct pci_dev *pdev,
> +				     struct cxl_dev_state *cxlds)
> +{
> +	struct cxl_register_map map;
> +	int rc;
> +
> +	rc = cxl_pci_setup_regs(pdev, CXL_REGLOC_RBI_MEMDEV, &map,
> +				cxlds->capabilities);
> +	/*
> +	 * This call can return -ENODEV if regs not found. This is not an error
> +	 * for Type2 since these regs are not mandatory. If they do exist then
> +	 * mapping them should not fail. If they should exist, it is with driver
> +	 * calling cxl_pci_check_caps where the problem should be found.
> +	 */

There is no common definition of type-2 so the core should not try to
assume it knows, or be told what is mandatory. Just export the raw
helpers and leave it to the caller to make these decisions.

> +	if (rc == -ENODEV)
> +		return 0;
> +
> +	if (rc)
> +		return rc;
> +
> +	return cxl_map_device_regs(&map, &cxlds->regs.device_regs);
> +}
> +
> +int cxl_pci_accel_setup_regs(struct pci_dev *pdev, struct cxl_dev_state *cxlds)
> +{
> +	int rc;
> +
> +	rc = cxl_pci_setup_memdev_regs(pdev, cxlds);
> +	if (rc)
> +		return rc;
> +
> +	rc = cxl_pci_setup_regs(pdev, CXL_REGLOC_RBI_COMPONENT,
> +				&cxlds->reg_map, cxlds->capabilities);
> +	if (rc) {
> +		dev_warn(&pdev->dev, "No component registers (%d)\n", rc);
> +		return rc;
> +	}
> +
> +	if (!test_bit(CXL_CM_CAP_CAP_ID_RAS, cxlds->capabilities))
> +		return rc;
> +
> +	rc = cxl_map_component_regs(&cxlds->reg_map,
> +				    &cxlds->regs.component,
> +				    BIT(CXL_CM_CAP_CAP_ID_RAS));
> +	if (rc)
> +		dev_dbg(&pdev->dev, "Failed to map RAS capability.\n");
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_pci_accel_setup_regs, "CXL");

Only after we have multiple instances of CXL accelerator drivers that
start copying the same init code should a helper be created that wraps
that duplication. Otherwise move this probing and error determination
out to SFC for now.