Re: [PATCH 07/25] scsi: hisi_sas: add ioremap for device HW

[zhangfei]

On 10/13/2015 08:20 PM, Arnd Bergmann wrote:
> On Tuesday 13 October 2015 17:47:02 zhangfei wrote:
> > On 10/12/2015 11:21 PM, Arnd Bergmann wrote:
> > > On Monday 12 October 2015 23:20:19 John Garry wrote:
> > > > +int hisi_sas_ioremap(struct hisi_hba *hisi_hba)
> > > > +{
> > > > +       struct platform_device *pdev = hisi_hba->pdev;
> > > > +       struct device *dev = &pdev->dev;
> > > > +       struct resource *res;
> > > > +
> > > > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > > +       hisi_hba->regs = devm_ioremap(dev,
> > > > +                                     res->start,
> > > > +                                     resource_size(res));
> > > > +       if (!hisi_hba->regs)
> > > > +               return -ENOMEM;
> > > > +
> > > > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> > > > +       hisi_hba->ctrl_regs = devm_ioremap(dev,
> > > > +                                          res->start,
> > > > +                                          resource_size(res));
> > > > +       if (!hisi_hba->ctrl_regs)
> > > > +               return -ENOMEM;
> > > > +
> > > > +       return 0;
> > > > +}
> > > >
> > > >    static const struct of_device_id sas_of_match[] = {
> > >
> > > Better use devm_ioremap_resource() here, which registers the resource so they
> > > are checked for conflicts and listed in /proc/iomem.
> >
> > Yes, hisi_hba->regs can use devm_ioremap_resource.
> >
> > However ctrl_regs have to use devm_ioremap, since the address are
> > sharing among different nodes, unfortunately, and devm_ioremap_resource
> > will fail.
>
> This sounds like it should be fixed in the DT binding then, to ensure
> that the ranges don't overlap.
>
> Mapping the same register region multiple times is generally considered
> a bad idea because the drivers that map them often don't have global
> locks that serialize the access, so it's better to have code in place
> that ensures that they are distinct.
>
> What is the purpose of the ctrl_regs region, and why is it shared
> across multiple devices?
>
> Are all users of these registers in the same driver?

We are considering using syscon for ctrl_regs.

Thanks Arnd.

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