Re: [PATCH v3 6/8] cxl: create emulated decoders for devices without HDM decoders

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Wed, 18 Jan 2023 11:09:12 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

> CXL rev3.0 spec 8.1.3
> 
> RCDs may not have HDM register blocks. Create fake decoders based on CXL
> PCIe DVSEC registers. The DVSEC Range Registers provide the memory range
> for these decoder structs. For the RCD, there can be up to 2 decoders
> depending on the DVSEC Capability register HDM_count.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
FWIW
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> ---
> v3:
> - Drop unrelated bits from patch. (Jonathan)
> ---
>  drivers/cxl/core/hdm.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 86fe1be2e961..cbec955db4c9 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -748,6 +748,13 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
>  	if (is_endpoint_decoder(&cxld->dev))
>  		cxled = to_cxl_endpoint_decoder(&cxld->dev);
>  
> +	if (!hdm) {
> +		if (!cxled)
> +			return -EINVAL;
> +
> +		return cxl_setup_hdm_decoder_from_dvsec(port, cxld, which, info);
> +	}
> +
>  	ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(which));
>  	base = ioread64_hi_lo(hdm + CXL_HDM_DECODER0_BASE_LOW_OFFSET(which));
>  	size = ioread64_hi_lo(hdm + CXL_HDM_DECODER0_SIZE_LOW_OFFSET(which));
> 
>