Re: [PATCH v24 06/11] cxl/hdm: Add support for getting region from committed decoder

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

On 3/23/26 4:31 AM, alejandro.lucero-palau@amd.com wrote:
> From: Alejandro Lucero <alucerop@amd.com>
> 

Maybe subject should be "Add helper function to retrieve a committed decoder and its region"?

> A Type2 device configured by the BIOS can already have its HDM
> committed. Add a cxl_get_committed_decoder() function for cheking
> so after memdev creation. A CXL region should have been created

Sentence doesn't quite make sense to me.

> during memdev initialization, therefore a Type2 driver can ask for
> such a region for working with the HPA. If the HDM is not committed,
> a Type2 driver will create the region after obtaining proper HPA
> and DPA space.
> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> ---
>  drivers/cxl/core/hdm.c | 39 +++++++++++++++++++++++++++++++++++++++
>  include/cxl/cxl.h      |  3 +++
>  2 files changed, 42 insertions(+)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index c222e98ae736..006be88efaa5 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -686,6 +686,45 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, u64 size)
>  	return devm_add_action_or_reset(&port->dev, cxl_dpa_release, cxled);
>  }
>  
> +static int find_committed_endpoint_decoder(struct device *dev, const void *data)
> +{
> +	struct cxl_endpoint_decoder *cxled;
> +	struct cxl_port *port;
> +
> +	if (!is_endpoint_decoder(dev))
> +		return 0;
> +
> +	cxled = to_cxl_endpoint_decoder(dev);
> +	port = cxled_to_port(cxled);
> +
> +	return cxled->cxld.id == port->hdm_end;
> +}
> +
> +struct cxl_endpoint_decoder *cxl_get_committed_decoder(struct cxl_memdev *cxlmd,
> +						       struct cxl_region **cxlr)

kdoc header for this exported function?

> +{
> +	struct cxl_port *endpoint = cxlmd->endpoint;
> +	struct cxl_endpoint_decoder *cxled;
> +	struct device *cxled_dev;
> +
> +	if (!endpoint)
> +		return NULL;
> +
> +	guard(rwsem_read)(&cxl_rwsem.dpa);
> +	cxled_dev = device_find_child(&endpoint->dev, NULL,
> +				      find_committed_endpoint_decoder);
> +
> +	if (!cxled_dev)
> +		return NULL;
> +
> +	cxled = to_cxl_endpoint_decoder(cxled_dev);
> +	*cxlr = cxled->cxld.region;

Should SFC take a ref on the region device?

> +
> +	put_device(cxled_dev);

Maybe should let the caller release the reference? I think you will want to hold the reference by SFC until you no longer need the decoder?

DJ 

> +	return cxled;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_get_committed_decoder, "CXL");
> +
>  static void cxld_set_interleave(struct cxl_decoder *cxld, u32 *ctrl)
>  {
>  	u16 eig;
> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
> index 10a9b8fa2f6b..2a61138e2a73 100644
> --- a/include/cxl/cxl.h
> +++ b/include/cxl/cxl.h
> @@ -231,4 +231,7 @@ struct cxl_dev_state *_devm_cxl_dev_state_create(struct device *dev,
>  int cxl_set_capacity(struct cxl_dev_state *cxlds, u64 capacity);
>  struct cxl_memdev *devm_cxl_add_memdev(struct cxl_dev_state *cxlds,
>  				       const struct cxl_memdev_attach *attach);
> +struct cxl_region;
> +struct cxl_endpoint_decoder *cxl_get_committed_decoder(struct cxl_memdev *cxlmd,
> +						       struct cxl_region **cxlr);
>  #endif /* __CXL_CXL_H__ */