Re: [PATCH v2] cxl/hdm: Extend DVSEC range register emulation for region enumeration

[Dave Jiang <dave.jiang@intel.com>]

On 4/3/23 4:06 PM, Dan Williams wrote:
> One motivation for mapping range registers to decoder objects is
> to use those settings for region autodiscovery.
> 
> The need to map a region for devices programmed to use range registers
> is especially urgent now that the kernel no longer routes "Soft
> Reserved" ranges in the memory map to device-dax by default. The CXL
> memory range loses all access mechanisms.
> 
> Complete the implementation by filling out ways and granularity, marking
> the DPA reservation, and setting the endpoint-decoder state to signal
> autodiscovery.

If you don't mind making a note that the default values of ways and 
granularity are coming from cxl_decode_init(). Thanks.

> 
> Fixes: 09d09e04d2fc ("cxl/dax: Create dax devices for CXL RAM regions")
> Tested-by: Dave Jiang <dave.jiang@intel.com>
> Tested-by: Gregory Price <gregory.price@memverge.com>
> Link: https://lore.kernel.org/r/168012575521.221280.14177293493678527326.stgit@dwillia2-xfh.jf.intel.com
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

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

> ---
> Changes since v1:
> - Swap out the local @range variable which was mostly only used for the
>    mapping length with a @len variable for that purpose (Jonathan)
> 
>   drivers/cxl/core/hdm.c |   27 ++++++++++++++++++++++-----
>   1 file changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 9884b6d4d930..02cc2c38b44b 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -738,14 +738,20 @@ static int cxl_decoder_reset(struct cxl_decoder *cxld)
>   	return 0;
>   }
>   
> -static int cxl_setup_hdm_decoder_from_dvsec(struct cxl_port *port,
> -					    struct cxl_decoder *cxld, int which,
> -					    struct cxl_endpoint_dvsec_info *info)
> +static int cxl_setup_hdm_decoder_from_dvsec(
> +	struct cxl_port *port, struct cxl_decoder *cxld, u64 *dpa_base,
> +	int which, struct cxl_endpoint_dvsec_info *info)
>   {
> +	struct cxl_endpoint_decoder *cxled;
> +	u64 len;
> +	int rc;
> +
>   	if (!is_cxl_endpoint(port))
>   		return -EOPNOTSUPP;
>   
> -	if (!range_len(&info->dvsec_range[which]))
> +	cxled = to_cxl_endpoint_decoder(&cxld->dev);
> +	len = range_len(&info->dvsec_range[which]);
> +	if (!len)
>   		return -ENOENT;
>   
>   	cxld->target_type = CXL_DECODER_EXPANDER;
> @@ -760,6 +766,16 @@ static int cxl_setup_hdm_decoder_from_dvsec(struct cxl_port *port,
>   	cxld->flags |= CXL_DECODER_F_ENABLE | CXL_DECODER_F_LOCK;
>   	port->commit_end = cxld->id;
>   
> +	rc = devm_cxl_dpa_reserve(cxled, *dpa_base, len, 0);
> +	if (rc) {
> +		dev_err(&port->dev,
> +			"decoder%d.%d: Failed to reserve DPA range %#llx - %#llx\n (%d)",
> +			port->id, cxld->id, *dpa_base, *dpa_base + len - 1, rc);
> +		return rc;
> +	}
> +	*dpa_base += len;
> +	cxled->state = CXL_DECODER_STATE_AUTO;
> +
>   	return 0;
>   }
>   
> @@ -779,7 +795,8 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
>   	} target_list;
>   
>   	if (should_emulate_decoders(info))
> -		return cxl_setup_hdm_decoder_from_dvsec(port, cxld, which, info);
> +		return cxl_setup_hdm_decoder_from_dvsec(port, cxld, dpa_base,
> +							which, info);
>   
>   	ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(which));
>   	base = ioread64_hi_lo(hdm + CXL_HDM_DECODER0_BASE_LOW_OFFSET(which));
>