Re: [PATCH] cxl/hdm: Fix decoder count calculation

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

On Thu, 10 Jun 2021 14:53:32 -0700
Ben Widawsky <ben.widawsky@intel.com> wrote:

> The decoder count in the HDM decoder capability structure is an encoded
> field. As defined in the spec:
> 
> Decoder Count: Reports the number of memory address decoders implemented
> by the component.
> 0 – 1 Decoder
> 1 – 2 Decoders
> 2 – 4 Decoders
> 3 – 6 Decoders
> 4 – 8 Decoders
> 5 – 10 DecodersAll other values are reserved
> 
> Nothing is actually fixed by this as nothing actually used this mapping
> yet.
> 
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
lgtm.

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

> ---
>  drivers/cxl/core.c | 3 ++-
>  drivers/cxl/cxl.h  | 1 +
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/core.c b/drivers/cxl/core.c
> index cda09a9cd98e..92db02fe7aa8 100644
> --- a/drivers/cxl/core.c
> +++ b/drivers/cxl/core.c
> @@ -666,7 +666,8 @@ void cxl_probe_component_regs(struct device *dev, void __iomem *base,
>  
>  			hdr = readl(register_block);
>  
> -			decoder_cnt = FIELD_GET(CXL_HDM_DECODER_COUNT_MASK, hdr);
> +			decoder_cnt =
> +				cxl_hdm_decoder_count(FIELD_GET(CXL_HDM_DECODER_COUNT_MASK, hdr));
>  			length = 0x20 * decoder_cnt + 0x10;
>  
>  			map->hdm_decoder.valid = true;
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 1ffc5e07e24d..f0dff7d96286 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -35,6 +35,7 @@
>  /* HDM decoders CXL 2.0 8.2.5.12 CXL HDM Decoder Capability Structure */
>  #define CXL_HDM_DECODER_CAP_OFFSET 0x0
>  #define   CXL_HDM_DECODER_COUNT_MASK GENMASK(3, 0)
> +#define	    cxl_hdm_decoder_count(bits) ((bits) == 0 ? 1 : (bits) * 2)
>  #define   CXL_HDM_DECODER_TARGET_COUNT_MASK GENMASK(7, 4)
>  #define CXL_HDM_DECODER0_BASE_LOW_OFFSET 0x10
>  #define CXL_HDM_DECODER0_BASE_HIGH_OFFSET 0x14