netdev - Re: [PATCH v18 04/20] cxl: allow Type2 drivers to map cxl component regs

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Message-ID: <20250918120348.000028a5@huawei.com>
Date: Thu, 18 Sep 2025 12:03:48 +0100
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: <alejandro.lucero-palau@....com>
CC: <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>, Alejandro Lucero <alucerop@....com>
Subject: Re: [PATCH v18 04/20] cxl: allow Type2 drivers to map cxl component
 regs

On Thu, 18 Sep 2025 10:17:30 +0100
alejandro.lucero-palau@....com wrote:

> From: Alejandro Lucero <alucerop@....com>
> 
> Export cxl core functions for a Type2 driver being able to discover and
> map the device component registers.
> 
> Use it in sfc driver cxl initialization.
> 
> Signed-off-by: Alejandro Lucero <alucerop@....com>
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> diff --git a/drivers/net/ethernet/sfc/efx_cxl.c b/drivers/net/ethernet/sfc/efx_cxl.c
> index 56d148318636..cdfbe546d8d8 100644
> --- a/drivers/net/ethernet/sfc/efx_cxl.c
> +++ b/drivers/net/ethernet/sfc/efx_cxl.c
> @@ -5,6 +5,7 @@
>   * Copyright (C) 2025, Advanced Micro Devices, Inc.
>   */
>  
> +#include <cxl/cxl.h>
>  #include <cxl/pci.h>
>  #include <linux/pci.h>
>  
> @@ -19,6 +20,7 @@ int efx_cxl_init(struct efx_probe_data *probe_data)
>  	struct pci_dev *pci_dev = efx->pci_dev;
>  	struct efx_cxl *cxl;
>  	u16 dvsec;
> +	int rc;
>  
>  	probe_data->cxl_pio_initialised = false;
>  
> @@ -45,6 +47,37 @@ int efx_cxl_init(struct efx_probe_data *probe_data)
>  	if (!cxl)
>  		return -ENOMEM;
>  
> +	rc = cxl_pci_setup_regs(pci_dev, CXL_REGLOC_RBI_COMPONENT,
> +				&cxl->cxlds.reg_map);
> +	if (rc) {
> +		dev_err(&pci_dev->dev, "No component registers (err=%d)\n", rc);
> +		return rc;
> +	}
> +
> +	if (!cxl->cxlds.reg_map.component_map.hdm_decoder.valid) {
> +		dev_err(&pci_dev->dev, "Expected HDM component register not found\n");
> +		return -ENODEV;
> +	}
> +
> +	if (!cxl->cxlds.reg_map.component_map.ras.valid)
> +		return dev_err_probe(&pci_dev->dev, -ENODEV,
> +				     "Expected RAS component register not found\n");

Why the mix of dev_err() and dev_err_probe()?
I'd prefer dev_err_probe() for all these, but we definitely don't
want a mix.

> +
> +	rc = cxl_map_component_regs(&cxl->cxlds.reg_map,
> +				    &cxl->cxlds.regs.component,
> +				    BIT(CXL_CM_CAP_CAP_ID_RAS));
> +	if (rc) {
> +		dev_err(&pci_dev->dev, "Failed to map RAS capability.\n");
> +		return rc;
> +	}
> +
> +	/*
> +	 * Set media ready explicitly as there are neither mailbox for checking
> +	 * this state nor the CXL register involved, both not mandatory for
> +	 * type2.
> +	 */
> +	cxl->cxlds.media_ready = true;
> +
>  	probe_data->cxl = cxl;
>  
>  	return 0;
> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
> index 13d448686189..3b9c8cb187a3 100644
> --- a/include/cxl/cxl.h
> +++ b/include/cxl/cxl.h

> +/**
> + * cxl_map_component_regs - map cxl component registers
> + *

Why 2 blank lines?

> + *
> + * @map: cxl register map to update with the mappings
> + * @regs: cxl component registers to work with
> + * @map_mask: cxl component regs to map
> + *
> + * Returns integer: success (0) or error (-ENOMEM)
> + *
> + * Made public for Type2 driver support.
> + */
> +int cxl_map_component_regs(const struct cxl_register_map *map,
> +			   struct cxl_component_regs *regs,
> +			   unsigned long map_mask);
>  #endif /* __CXL_CXL_H__ */
		       struct cxl_register_map *map);