Re: [PATCH v4 06/14] cxl/region: Separate region parameter setup and region construction

[Jonathan Cameron]

On Fri, 7 Nov 2025 16:59:25 +0100
Robert Richter <rrichter@xxxxxxx> wrote:

> On 03.11.25 15:05:28, Dave Jiang wrote:
> > 
> > 
> > On 11/3/25 11:47 AM, Robert Richter wrote:  
> > > To construct a region, the region parameters such as address range and
> > > interleaving config need to be determined. This is done while
> > > constructing the region by inspecting the endpoint decoder
> > > configuration. The endpoint decoder is passed as a function argument.
> > > 
> > > With address translation the endpoint decoder data is no longer
> > > sufficient to extract the region parameters as some of the information
> > > is obtained using other methods such as using firmware calls.
> > > 
> > > In a first step, separate code to determine the region parameters from
> > > the region construction. Temporarily store all the data to create the
> > > region in the new struct cxl_region_context. Once the region data is
> > > determined and struct cxl_region_context is filled, construct the
> > > region.
> > > 
> > > Patch is a prerequisite to implement address translation. The code
> > > separation helps to later extend it to determine region parameters
> > > using other methods as needed, esp. to support address translation.
> > > 
> > > Reviewed-by: Gregory Price <gourry@xxxxxxxxxx>
> > > Signed-off-by: Robert Richter <rrichter@xxxxxxx>  
> > 
> > Just a small thing below, otherwise
> > Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> >   
> > > ---
> > >  drivers/cxl/core/core.h   |  9 +++++++++
> > >  drivers/cxl/core/region.c | 32 +++++++++++++++++++++-----------
> > >  2 files changed, 30 insertions(+), 11 deletions(-)
> > > 
> > > diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> > > index 1fb66132b777..2bc37f3aee21 100644
> > > --- a/drivers/cxl/core/core.h
> > > +++ b/drivers/cxl/core/core.h
> > > @@ -19,6 +19,15 @@ enum cxl_detach_mode {
> > >  };
> > >  
> > >  #ifdef CONFIG_CXL_REGION
> > > +
> > > +struct cxl_region_context {
> > > +	struct cxl_endpoint_decoder *cxled;
> > > +	struct cxl_memdev *cxlmd;  
> > 
> > cxlmd may not be needed.
> > 
> > struct cxl_memdev *cxlmd = cxled_to_memdev(cxlr_ctx->cxled);
> > 
> > which you used later on in this patch to init the cxlmd member :)  
> 
> This was on purpose to eliminate an unnecessary frequent call of
> cxled_to_memdev() while holding the context. There is at least a
> 3-level pointer chasing to get to cxlmd.
> 
> Maybe it's wort to add it to struct cxl_endpoint_decoder.

This isn't high performance code and the helper is there so I'd just
use it as Dave suggested.

Jonathan

> 
> -Robert
>