Re: [PATCH v12 07/23] cxl: support dpa initialization without a mailbox

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

On Mon, 31 Mar 2025 15:45:39 +0100
alejandro.lucero-palau@amd.com wrote:

> From: Alejandro Lucero <alucerop@amd.com>
> 
> Type3 relies on mailbox CXL_MBOX_OP_IDENTIFY command for initializing
> memdev state params which end up being used for dma initialization.

DMA

> 
> Allow a Type2 driver to initialize dpa simply by giving the size of its

DPA

> volatile and/or non-volatile hardware partitions.
> 
> Export cxl_dpa_setup as well for initializing those added dpa partitions
> with the proper resources.
> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Reviewed-by: Ben Cheatham <benjamin.cheatham@amd.com>
> ---
>  drivers/cxl/core/mbox.c | 17 ++++++++++++++---
>  drivers/cxl/cxlmem.h    | 13 -------------
>  include/cxl/cxl.h       | 14 ++++++++++++++
>  3 files changed, 28 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index ab994d459f46..e4610e778723 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -1284,6 +1284,18 @@ static void add_part(struct cxl_dpa_info *info, u64 start, u64 size, enum cxl_pa
>  	info->nr_partitions++;
>  }
>  
> +void cxl_mem_dpa_init(struct cxl_dpa_info *info, u64 volatile_bytes,
> +		      u64 persistent_bytes)
> +{
> +	if (!info->size)

Why?  What is this defending against?

> +		info->size = volatile_bytes + persistent_bytes;
> +
> +	add_part(info, 0, volatile_bytes, CXL_PARTMODE_RAM);
> +	add_part(info, volatile_bytes, persistent_bytes,
> +		 CXL_PARTMODE_PMEM);
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_mem_dpa_init, "CXL");