linux-kernel - Re: [PATCH v2 1/5] cxl/mem: Introduce cxl_decode_register

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Date:   Tue, 25 May 2021 10:53:04 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     <ira.weiny@...el.com>
CC:     Ben Widawsky <ben.widawsky@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] cxl/mem: Introduce cxl_decode_register_block()

On Fri, 21 May 2021 17:11:50 -0700
<ira.weiny@...el.com> wrote:

> From: Ira Weiny <ira.weiny@...el.com>
> 
> Each register block located in the DVSEC needs to be decoded from 2
> words, 'register offset high' and 'register offset low'.
> 
> Create a function, cxl_decode_register_block() to perform this decode
> and return the bar, offset, and register type of the register block.
> 
> Then use the values decoded in cxl_mem_map_regblock() instead of passing
> the raw registers.
> 
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
Makes sense to factor this out.

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

> 
> ---
> Changes for V2:
> 	Push this to the start of the series
> ---
>  drivers/cxl/pci.c | 26 ++++++++++++++++++--------
>  1 file changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 8bdae74d7d78..b2f978954daa 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -922,17 +922,13 @@ static struct cxl_mem *cxl_mem_create(struct pci_dev *pdev)
>  	return cxlm;
>  }
>  
> -static void __iomem *cxl_mem_map_regblock(struct cxl_mem *cxlm, u32 reg_lo, u32 reg_hi)
> +static void __iomem *cxl_mem_map_regblock(struct cxl_mem *cxlm,
> +					  u8 bar, u64 offset)
>  {
>  	struct pci_dev *pdev = cxlm->pdev;
>  	struct device *dev = &pdev->dev;
> -	u64 offset;
> -	u8 bar;
>  	int rc;
>  
> -	offset = ((u64)reg_hi << 32) | (reg_lo & CXL_REGLOC_ADDR_MASK);
> -	bar = FIELD_GET(CXL_REGLOC_BIR_MASK, reg_lo);
> -
>  	/* Basic sanity check that BAR is big enough */
>  	if (pci_resource_len(pdev, bar) < offset) {
>  		dev_err(dev, "BAR%d: %pr: too small (offset: %#llx)\n", bar,
> @@ -974,6 +970,14 @@ static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec)
>  	return 0;
>  }
>  
> +static void cxl_decode_register_block(u32 reg_lo, u32 reg_hi,
> +				      u8 *bar, u64 *offset, u8 *reg_type)
> +{
> +	*offset = ((u64)reg_hi << 32) | (reg_lo & CXL_REGLOC_ADDR_MASK);
> +	*bar = FIELD_GET(CXL_REGLOC_BIR_MASK, reg_lo);
> +	*reg_type = FIELD_GET(CXL_REGLOC_RBI_MASK, reg_lo);
> +}
> +
>  /**
>   * cxl_mem_setup_regs() - Setup necessary MMIO.
>   * @cxlm: The CXL memory device to communicate with.
> @@ -1009,15 +1013,21 @@ static int cxl_mem_setup_regs(struct cxl_mem *cxlm)
>  	for (i = 0; i < regblocks; i++, regloc += 8) {
>  		u32 reg_lo, reg_hi;
>  		u8 reg_type;
> +		u64 offset;
> +		u8 bar;
>  
>  		/* "register low and high" contain other bits */
>  		pci_read_config_dword(pdev, regloc, &reg_lo);
>  		pci_read_config_dword(pdev, regloc + 4, &reg_hi);
>  
> -		reg_type = FIELD_GET(CXL_REGLOC_RBI_MASK, reg_lo);
> +		cxl_decode_register_block(reg_lo, reg_hi, &bar, &offset,
> +					  &reg_type);
> +
> +		dev_dbg(dev, "Found register block in bar %u @ 0x%llx of type %u\n",
> +			bar, offset, reg_type);
>  
>  		if (reg_type == CXL_REGLOC_RBI_MEMDEV) {
> -			base = cxl_mem_map_regblock(cxlm, reg_lo, reg_hi);
> +			base = cxl_mem_map_regblock(cxlm, bar, offset);
>  			if (IS_ERR(base))
>  				return PTR_ERR(base);
>  			break;