Re: [PATCH 02/26] cxl/core: Separate region mode from decoder mode

Jonathan Cameron
2024-03-25T16:20:14Z

On Sun, 24 Mar 2024 16:18:05 -0700
ira.weiny@intel.com wrote:

> From: Navneet Singh <navneet.singh@intel.com>
>
> Until now region modes and decoder modes were equivalent in that they
> were either PMEM or RAM. With the upcoming addition of Dynamic Capacity
> regions (which will represent an array of device regions [better named
> partitions] the index of which could be different on different
> interleaved devices), the mode of an endpoint decoder and a region will
> no longer be equivalent.
>
> Define a new region mode enumeration and adjust the code for it.
>
> Suggested-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
> Signed-off-by: Navneet Singh <navneet.singh@intel.com>
> Co-developed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

I can't really remember the reasoning behind this split, but from a fresh
read it seems reasonable. Some trivial comments inline.

Jonathan

>
> ---
> Changes for v1
> <none>
> ---
> drivers/cxl/core/region.c | 77 +++++++++++++++++++++++++++++++++++------------
> drivers/cxl/cxl.h | 26 ++++++++++++++--
> 2 files changed, 81 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 4c7fd2d5cccb..1723d17f121e 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c

> @@ -2800,6 +2814,24 @@ static int match_region_by_range(struct device *dev, void *data)
> return rc;
> }
>
> +static enum cxl_region_mode
> +cxl_decoder_to_region_mode(enum cxl_decoder_mode mode)
> +{
> + switch (mode) {
> + case CXL_DECODER_NONE:
> + return CXL_REGION_NONE;
> + case CXL_DECODER_RAM:
> + return CXL_REGION_RAM;
> + case CXL_DECODER_PMEM:
> + return CXL_REGION_PMEM;
> + case CXL_DECODER_MIXED:
> + default:
> + return CXL_REGION_MIXED;
> + }
> +

Dead code.

> + return CXL_REGION_MIXED;
> +}
> +
> /* Establish an empty region covering the given HPA range */
> static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> struct cxl_endpoint_decoder *cxled)
> @@ -2808,12 +2840,17 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> struct cxl_port *port = cxlrd_to_port(cxlrd);
> struct range *hpa = &cxled->cxld.hpa_range;
> struct cxl_region_params *p;
> + enum cxl_region_mode mode;
> struct cxl_region *cxlr;
> struct resource *res;
> int rc;
>
> + if (cxled->mode == CXL_DECODER_DEAD)
> + return ERR_PTR(-EINVAL);

Not a bad thing necessarily, but why do we now need this and didn't before?

> +
> + mode = cxl_decoder_to_region_mode(cxled->mode);
> do {
> - cxlr = __create_region(cxlrd, cxled->mode,
> + cxlr = __create_region(cxlrd, mode,
> atomic_read(&cxlrd->region_id));
> } while (IS_ERR(cxlr) && PTR_ERR(cxlr) == -EBUSY);

> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 003feebab79b..9a0cce1e6fca 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h

> /*
> * Track whether this decoder is reserved for region autodiscovery, or
> * free for userspace provisioning.
> @@ -511,7 +532,8 @@ struct cxl_region_params {
> * struct cxl_region - CXL region
> * @dev: This region's device
> * @id: This region's id. Id is globally unique across all regions
> - * @mode: Endpoint decoder allocation / access mode
> + * @mode: Region mode which defines which endpoint decoder mode the region is
mode or potentially modes?

If region is mixed, I guess that means endpoint could be pmem or ram in theory?
Don't think anyone has implemented anything yet, but is the potential there?

> + * compatible with