Re: [RFC PATCH v2 12/28] cxl/core: Store component register base for memdevs

From: Ben Widawsky <ben.widawsky@intel.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-cxl@vger.kernel.org,
	Chet Douglas <chet.r.douglas@intel.com>,
	Alison Schofield <alison.schofield@intel.com>,
	Ira Weiny <ira.weiny@intel.com>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Vishal Verma <vishal.l.verma@intel.com>
Subject: Re: [RFC PATCH v2 12/28] cxl/core: Store component register base for memdevs
Date: Mon, 1 Nov 2021 14:50:40 -0700	[thread overview]
Message-ID: <20211101215040.tfapgsw66acn4up4@intel.com> (raw)
In-Reply-To: <CAPcyv4gR0w4CFPsDoiBd6o=ZyToiyRWFuj8GfTNieOeopHwLEg@mail.gmail.com>

On 21-10-31 13:13:32, Dan Williams wrote:
> On Fri, Oct 22, 2021 at 11:37 AM Ben Widawsky <ben.widawsky@intel.com> wrote:
> >

[snip]

> > -       cxlmd = devm_cxl_add_memdev(cxlm);
> > +       /*
> > +        * If the component registers can't be found, the cxl_pci driver may
> > +        * still be useful for management functions so don't return an error.
> 
> This comment makes sense...
> 
> > +        *
> > +        * XXX: Creating the device is going to kick of the cxl_mem probing.
> > +        * That probe requires the component registers. Therefore, the register
> > +        * block must always be found first.
> > +        */
> 
> ..., but I don't understand the point of this comment. Given that
> devm_cxl_add_memdev() takes the base address as an argument it's
> already clear that the component registers need to be found before
> devm_cxl_add_memdev().
> 

That comment was created before devm_cxl_add_memdev() took the base. Indeed the
comment no longer makes sense.

> > +       rc = cxl_find_regblock(pdev, CXL_REGLOC_RBI_COMPONENT, &map);
> > +       if (rc)
> > +               dev_warn(&cxlmd->dev, "No component registers (%d)\n", rc);
> > +       else
> > +               creg = cxl_reg_block(pdev, &map);
> > +
> > +       cxlmd = devm_cxl_add_memdev(cxlm, creg);
> >         if (IS_ERR(cxlmd))
> >                 return PTR_ERR(cxlmd);
> >
> > diff --git a/tools/testing/cxl/test/mem.c b/tools/testing/cxl/test/mem.c
> > index 12a8437a9ca0..471fc7fb5418 100644
> > --- a/tools/testing/cxl/test/mem.c
> > +++ b/tools/testing/cxl/test/mem.c
> > @@ -227,7 +227,8 @@ static int cxl_mock_mem_probe(struct platform_device *pdev)
> >         if (rc)
> >                 return rc;
> >
> > -       cxlmd = devm_cxl_add_memdev(cxlm);
> > +       /* TODO: mock component registers, or... */
> 
> How about:
> 
> /* cxl_test does not emulate registers, any memdev operations that
> imply component register access will be mocked at the memdev
> operations interface */
> 

Sounds good to me.

> > +       cxlmd = devm_cxl_add_memdev(cxlm, CXL_RESOURCE_NONE);
> >         if (IS_ERR(cxlmd))
> >                 return PTR_ERR(cxlmd);
> >
> > --
> > 2.33.1
> >