linux-kernel - Re: [PATCH v7 2/5] cxl: Add functions to get an instance of / count regblocks of a given type

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Message-ID: <670f8541-fbf2-8992-da88-78c3af925495@intel.com>
Date:   Tue, 30 May 2023 10:10:18 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Liang Kan <kan.liang@...ux.intel.com>,
        <linux-cxl@...r.kernel.org>, <peterz@...radead.org>,
        <mark.rutland@....com>, <will@...nel.org>,
        <dan.j.williams@...el.com>
CC:     <mingo@...hat.com>, <acme@...nel.org>, <linuxarm@...wei.com>,
        <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Namhyung Kim <namhyung@...il.com>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v7 2/5] cxl: Add functions to get an instance of / count
 regblocks of a given type


On 5/26/23 02:58, Jonathan Cameron wrote:
> Until the recently release CXL 3.0 specification, there
> was only ever one instance of any given register block pointed
> to by the Register Block Locator DVSEC. Now, the specification allows
> for multiple CXL PMU instances, each with their own register block.
>
> To enable this add cxl_find_regblock_instance() that takes an index
> parameter and use that to implement cxl_count_regblock() and
> cxl_find_regblock().
>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>


> ---
>   drivers/cxl/core/regs.c | 59 ++++++++++++++++++++++++++++++++++++-----
>   drivers/cxl/cxl.h       |  3 +++
>   2 files changed, 56 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
> index 1476a0299c9b..4b9672db867d 100644
> --- a/drivers/cxl/core/regs.c
> +++ b/drivers/cxl/core/regs.c
> @@ -286,20 +286,23 @@ static bool cxl_decode_regblock(struct pci_dev *pdev, u32 reg_lo, u32 reg_hi,
>   }
>   
>   /**
> - * cxl_find_regblock() - Locate register blocks by type
> + * cxl_find_regblock_instance() - Locate a register block by type / index
>    * @pdev: The CXL PCI device to enumerate.
>    * @type: Register Block Indicator id
>    * @map: Enumeration output, clobbered on error
> + * @index: Index into which particular instance of a regblock wanted in the
> + *	   order found in register locator DVSEC.
>    *
>    * Return: 0 if register block enumerated, negative error code otherwise
>    *
>    * A CXL DVSEC may point to one or more register blocks, search for them
> - * by @type.
> + * by @type and @index.
>    */
> -int cxl_find_regblock(struct pci_dev *pdev, enum cxl_regloc_type type,
> -		      struct cxl_register_map *map)
> +int cxl_find_regblock_instance(struct pci_dev *pdev, enum cxl_regloc_type type,
> +			       struct cxl_register_map *map, int index)
>   {
>   	u32 regloc_size, regblocks;
> +	int instance = 0;
>   	int regloc, i;
>   
>   	map->resource = CXL_RESOURCE_NONE;
> @@ -323,15 +326,59 @@ int cxl_find_regblock(struct pci_dev *pdev, enum cxl_regloc_type type,
>   		if (!cxl_decode_regblock(pdev, reg_lo, reg_hi, map))
>   			continue;
>   
> -		if (map->reg_type == type)
> -			return 0;
> +		if (map->reg_type == type) {
> +			if (index == instance)
> +				return 0;
> +			instance++;
> +		}
>   	}
>   
>   	map->resource = CXL_RESOURCE_NONE;
>   	return -ENODEV;
>   }
> +EXPORT_SYMBOL_NS_GPL(cxl_find_regblock_instance, CXL);
> +
> +/**
> + * cxl_find_regblock() - Locate register blocks by type
> + * @pdev: The CXL PCI device to enumerate.
> + * @type: Register Block Indicator id
> + * @map: Enumeration output, clobbered on error
> + *
> + * Return: 0 if register block enumerated, negative error code otherwise
> + *
> + * A CXL DVSEC may point to one or more register blocks, search for them
> + * by @type.
> + */
> +int cxl_find_regblock(struct pci_dev *pdev, enum cxl_regloc_type type,
> +		      struct cxl_register_map *map)
> +{
> +	return cxl_find_regblock_instance(pdev, type, map, 0);
> +}
>   EXPORT_SYMBOL_NS_GPL(cxl_find_regblock, CXL);
>   
> +/**
> + * cxl_count_regblock() - Count instances of a given regblock type.
> + * @pdev: The CXL PCI device to enumerate.
> + * @type: Register Block Indicator id
> + *
> + * Some regblocks may be repeated. Count how many instances.
> + *
> + * Return: count of matching regblocks.
> + */
> +int cxl_count_regblock(struct pci_dev *pdev, enum cxl_regloc_type type)
> +{
> +	struct cxl_register_map map;
> +	int rc, count = 0;
> +
> +	while (1) {
> +		rc = cxl_find_regblock_instance(pdev, type, &map, count);
> +		if (rc)
> +			return count;
> +		count++;
> +	}
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_count_regblock, CXL);
> +
>   resource_size_t cxl_rcrb_to_component(struct device *dev,
>   				      resource_size_t rcrb,
>   				      enum cxl_rcrb which)
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 044a92d9813e..f6e2a9ea5f41 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -260,6 +260,9 @@ int cxl_map_device_regs(struct device *dev, struct cxl_device_regs *regs,
>   			struct cxl_register_map *map);
>   
>   enum cxl_regloc_type;
> +int cxl_count_regblock(struct pci_dev *pdev, enum cxl_regloc_type type);
> +int cxl_find_regblock_instance(struct pci_dev *pdev, enum cxl_regloc_type type,
> +			       struct cxl_register_map *map, int index);
>   int cxl_find_regblock(struct pci_dev *pdev, enum cxl_regloc_type type,
>   		      struct cxl_register_map *map);
>