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Date:   Mon, 18 Oct 2021 10:30:29 +0100
From:   Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To:     Dan Williams <dan.j.williams@intel.com>
CC:     <linux-cxl@vger.kernel.org>, Ira Weiny <ira.weiny@intel.com>,
        <linux-pci@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 06/10] cxl/pci: Add @base to cxl_register_map
Message-ID: <20211018103029.0000538d@Huawei.com>
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        <163433497228.889435.11271988238496181536.stgit@dwillia2-desk3.amr.corp.intel.com>
Organization: Huawei Technologies Research and Development (UK) Ltd.
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On Fri, 15 Oct 2021 14:57:27 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> In addition to carrying @barno, @block_offset, and @reg_type, add @base
> to keep all map/unmap parameters in one object. The helpers
> cxl_{map,unmap}_regblock() handle adjusting @base to the @block_offset
> at map and unmap time.
> 
> Document that @base incorporates @block_offset so that downstream
> consumers of a mapped cxl_register_map instance do not need perform any
> fixups / can use @base directly.
> 
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> Changes since v5:
> - add kernel-doc for cxl_register_map to explain the interaction between
>   @base and @block_offset. (Ira and Jonathan)
> 
>  drivers/cxl/cxl.h |   10 ++++++++++
>  drivers/cxl/pci.c |   31 ++++++++++++++++---------------
>  2 files changed, 26 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index a6687e7fd598..5e2e93451928 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -139,7 +139,17 @@ struct cxl_device_reg_map {
>  	struct cxl_reg_map memdev;
>  };
>  
> +/**
> + * struct cxl_register_map - DVSEC harvested register block mapping parameters
> + * @base: virtual base of the register-block-BAR + @block_offset
> + * @block_offset: offset to start of register block in @barno
> + * @reg_type: see enum cxl_regloc_type
> + * @barno: PCI BAR number containing the register block
> + * @component_map: cxl_reg_map for component registers
> + * @device_map: cxl_reg_maps for device registers
> + */
>  struct cxl_register_map {
> +	void __iomem *base;
>  	u64 block_offset;
>  	u8 reg_type;
>  	u8 barno;
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index eb0c2f1b9e65..7d5e5548b316 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -306,8 +306,7 @@ static int cxl_pci_setup_mailbox(struct cxl_mem *cxlm)
>  	return 0;
>  }
>  
> -static void __iomem *cxl_pci_map_regblock(struct pci_dev *pdev,
> -					  struct cxl_register_map *map)
> +static int cxl_map_regblock(struct pci_dev *pdev, struct cxl_register_map *map)
>  {
>  	void __iomem *addr;
>  	int bar = map->barno;
> @@ -318,24 +317,27 @@ static void __iomem *cxl_pci_map_regblock(struct pci_dev *pdev,
>  	if (pci_resource_len(pdev, bar) < offset) {
>  		dev_err(dev, "BAR%d: %pr: too small (offset: %pa)\n", bar,
>  			&pdev->resource[bar], &offset);
> -		return NULL;
> +		return -ENXIO;
>  	}
>  
>  	addr = pci_iomap(pdev, bar, 0);
>  	if (!addr) {
>  		dev_err(dev, "failed to map registers\n");
> -		return addr;
> +		return -ENOMEM;
>  	}
>  
>  	dev_dbg(dev, "Mapped CXL Memory Device resource bar %u @ %pa\n",
>  		bar, &offset);
>  
> -	return addr;
> +	map->base = addr + map->block_offset;
> +	return 0;
>  }
>  
> -static void cxl_pci_unmap_regblock(struct pci_dev *pdev, void __iomem *base)
> +static void cxl_unmap_regblock(struct pci_dev *pdev,
> +			       struct cxl_register_map *map)
>  {
> -	pci_iounmap(pdev, base);
> +	pci_iounmap(pdev, map->base - map->block_offset);
> +	map->base = NULL;
>  }
>  
>  static int cxl_pci_dvsec(struct pci_dev *pdev, int dvsec)
> @@ -361,12 +363,12 @@ static int cxl_pci_dvsec(struct pci_dev *pdev, int dvsec)
>  	return 0;
>  }
>  
> -static int cxl_probe_regs(struct pci_dev *pdev, void __iomem *base,
> -			  struct cxl_register_map *map)
> +static int cxl_probe_regs(struct pci_dev *pdev, struct cxl_register_map *map)
>  {
>  	struct cxl_component_reg_map *comp_map;
>  	struct cxl_device_reg_map *dev_map;
>  	struct device *dev = &pdev->dev;
> +	void __iomem *base = map->base;
>  
>  	switch (map->reg_type) {
>  	case CXL_REGLOC_RBI_COMPONENT:
> @@ -442,7 +444,6 @@ static void cxl_decode_regblock(u32 reg_lo, u32 reg_hi,
>   */
>  static int cxl_pci_setup_regs(struct cxl_mem *cxlm)
>  {
> -	void __iomem *base;
>  	u32 regloc_size, regblocks;
>  	int regloc, i, n_maps, ret = 0;
>  	struct device *dev = cxlm->dev;
> @@ -475,12 +476,12 @@ static int cxl_pci_setup_regs(struct cxl_mem *cxlm)
>  		if (map->reg_type > CXL_REGLOC_RBI_MEMDEV)
>  			continue;
>  
> -		base = cxl_pci_map_regblock(pdev, map);
> -		if (!base)
> -			return -ENOMEM;
> +		ret = cxl_map_regblock(pdev, map);
> +		if (ret)
> +			return ret;
>  
> -		ret = cxl_probe_regs(pdev, base + map->block_offset, map);
> -		cxl_pci_unmap_regblock(pdev, base);
> +		ret = cxl_probe_regs(pdev, map);
> +		cxl_unmap_regblock(pdev, map);
>  		if (ret)
>  			return ret;
>  
>