linux-kernel - Re: [PATCH v3 06/10] cxl/pci: Add @base to cxl_register

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Date:   Wed, 13 Oct 2021 15:53:20 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Ira Weiny <ira.weiny@...el.com>
Cc:     linux-cxl@...r.kernel.org, Linux PCI <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v3 06/10] cxl/pci: Add @base to cxl_register_map

On Sat, Oct 9, 2021 at 9:21 PM Ira Weiny <ira.weiny@...el.com> wrote:
>
> On Sat, Oct 09, 2021 at 09:44:29AM -0700, Dan Williams wrote:
> > In addition to carrying @barno, @block_offset, and @reg_type, add @base
> > to keep all map/unmap parameters in one object. The helpers
> > cxl_{map,unmap}_regblock() handle adjusting @base to the @block_offset
> > at map and unmap time.
> >
> > Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> > ---
> >  drivers/cxl/cxl.h |    1 +
> >  drivers/cxl/pci.c |   31 ++++++++++++++++---------------
> >  2 files changed, 17 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> > index a6687e7fd598..7cd16ef144dd 100644
> > --- a/drivers/cxl/cxl.h
> > +++ b/drivers/cxl/cxl.h
> > @@ -140,6 +140,7 @@ struct cxl_device_reg_map {
> >  };
> >
> >  struct cxl_register_map {
> > +     void __iomem *base;
> >       u64 block_offset;
> >       u8 reg_type;
> >       u8 barno;
> > diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> > index 9f006299a0e3..b42407d067ac 100644
> > --- a/drivers/cxl/pci.c
> > +++ b/drivers/cxl/pci.c
> > @@ -306,8 +306,7 @@ static int cxl_pci_setup_mailbox(struct cxl_mem *cxlm)
> >       return 0;
> >  }
> >
> > -static void __iomem *cxl_pci_map_regblock(struct pci_dev *pdev,
> > -                                       struct cxl_register_map *map)
> > +static int cxl_map_regblock(struct pci_dev *pdev, struct cxl_register_map *map)
> >  {
> >       void __iomem *addr;
> >       int bar = map->barno;
> > @@ -318,24 +317,27 @@ static void __iomem *cxl_pci_map_regblock(struct pci_dev *pdev,
> >       if (pci_resource_len(pdev, bar) < offset) {
> >               dev_err(dev, "BAR%d: %pr: too small (offset: %#llx)\n", bar,
> >                       &pdev->resource[bar], (unsigned long long)offset);
> > -             return NULL;
> > +             return -ENXIO;
> >       }
> >
> >       addr = pci_iomap(pdev, bar, 0);
> >       if (!addr) {
> >               dev_err(dev, "failed to map registers\n");
> > -             return addr;
> > +             return -ENOMEM;
> >       }
> >
> >       dev_dbg(dev, "Mapped CXL Memory Device resource bar %u @ %#llx\n",
> >               bar, offset);
> >
> > -     return addr;
> > +     map->base = addr + map->block_offset;
> > +     return 0;
> >  }
> >
> > -static void cxl_pci_unmap_regblock(struct pci_dev *pdev, void __iomem *base)
> > +static void cxl_unmap_regblock(struct pci_dev *pdev,
> > +                            struct cxl_register_map *map)
> >  {
> > -     pci_iounmap(pdev, base);
> > +     pci_iounmap(pdev, map->base - map->block_offset);
>
> I know we need to get these in soon.  But I think map->base should be 'base'
> and map->block_offset should be handled in cxl_probe_regs() rather than
> subtract it here..

But why? The goal of the cxl_register_map cleanups is to reduce the
open-coding for details that can just be passed around in a @map
instance. Once cxl_map_regblock() sets up @base there's little reason
to consider the hardware regblock details.

> Either way this is cleaner than what it was.
>
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>

Thanks!