Re: [PATCH 3/5] cxl/acpi: Minimize granularity for x1 interleaves

[Alison Schofield <alison.schofield@intel.com>]

On Fri, Jul 22, 2022 at 05:56:09PM -0700, Dan Williams wrote:
> The kernel enforces that region granularity is >= to the top-level
> interleave-granularity for the given CXL window. However, when the CXL
> window interleave is x1, i.e. non-interleaved at the host bridge level,
> then the specified granularity does not matter. Override the window
> specified granularity to the CXL minimum so that any valid region
> granularity is >= to the root granularity.
> 
> Reported-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Alison Schofield <alison.schofield@intel.com>

> ---
>  drivers/cxl/acpi.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index eb436268b92c..67137e17b8c9 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -140,6 +140,12 @@ static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
>  		.end = res->end,
>  	};
>  	cxld->interleave_ways = ways;
> +	/*
> +	 * Minimize the x1 granularity to advertise support for any
> +	 * valid region granularity
> +	 */
> +	if (ways == 1)
> +		ig = 256;
>  	cxld->interleave_granularity = ig;
>  
>  	rc = cxl_decoder_add(cxld, target_map);
>