Re: [PATCH] cxl: Move register block enumeration to core

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Sep 21, 2021 at 07:07:13AM -0700, Dan Williams wrote:
> On Mon, Sep 20, 2021 at 3:57 PM Ben Widawsky <ben.widawsky@intel.com> wrote:
> >
> > CXL drivers or cxl_core itself will require the ability to map component
> > registers in order to map HDM decoder resources amongst other things.
> > Much of the register mapping code has already moved into cxl_core. The
> > code to pull the BAR number and block office remained within cxl_pci
> > because there was no need to move it. Upcoming work will require this
> > functionality to be available outside of cxl_pci.
> >
> > There are two intentional functional changes:
> > 1. cxl_pci: If there is more than 1 component, or device register block,
> >    only the first one (of each) is checked. Previous logic checked all
> >    duplicate register blocks and additionally attempted to map unused
> >    register blocks if present.
> > 2. cxl_pci: No more dev_dbg for unused register blocks
> 
> Why not break these out into separate patches before moving the code?
> It makes it easier to review, and it increases the precision of future
> Fixes: patches if necessary.

+1

> > +static int cxl_pci_dvsec(struct pci_dev *pdev, int dvsec)
> > +{
> > +       int pos;
> > +
> > +       pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DVSEC);
> > +       if (!pos)
> > +               return 0;
> > +
> > +       while (pos) {
> > +               u16 vendor, id;
> > +
> > +               pci_read_config_word(pdev, pos + PCI_DVSEC_HEADER1, &vendor);
> > +               pci_read_config_word(pdev, pos + PCI_DVSEC_HEADER2, &id);
> > +               if (vendor == PCI_DVSEC_VENDOR_ID_CXL && dvsec == id)
> > +                       return pos;
> > +
> > +               pos = pci_find_next_ext_capability(pdev, pos,
> > +                                                  PCI_EXT_CAP_ID_DVSEC);
> > +       }
> 
> We punted on refactoring this for the initial driver submission
> because it was difficult to coordinate. Now that cxl.git is an
> established tree, instead of moving this it seems time to address that
> refactor that Bjorn asked about. Bjorn, would you be willing to carry
> a non-rebasing branch with such a cleanup that CXL could pull from?

Sure.  Would be nice to get this cleaned up.