On Thu, Apr 27, 2023 at 5:15 AM Jiawen Wu <jiawenwu@xxxxxxxxxxxxxx> wrote:
> On Wednesday, April 26, 2023 11:45 PM, andy.shevchenko@xxxxxxxxx wrote:
> > Wed, Apr 26, 2023 at 03:14:27PM +0800, Jiawen Wu kirjoitti:
...
> > > +static int txgbe_i2c_request_regs(struct dw_i2c_dev *dev)
> > > +{
> > > + struct platform_device *pdev = to_platform_device(dev->dev);
> > > + struct resource *r;
> > > +
> > > + r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > + if (!r)
> > > + return -ENODEV;
> > > +
> > > + dev->base = devm_ioremap(&pdev->dev, r->start, resource_size(r));
> > > +
> > > + return PTR_ERR_OR_ZERO(dev->base);
> > > +}
> >
> > Redundant. See below.
...
> > > case MODEL_BAIKAL_BT1:
> > > ret = bt1_i2c_request_regs(dev);
> > > break;
> > > + case MODEL_WANGXUN_SP:
> > > + ret = txgbe_i2c_request_regs(dev);
> >
> > How is it different to...
> >
> > > + break;
> > > default:
> > > dev->base = devm_platform_ioremap_resource(pdev, 0);
> >
> > ...this one?
>
> devm_platform_ioremap_resource() has one more devm_request_mem_region()
> operation than devm_ioremap(). By my test, this memory cannot be re-requested,
> only re-mapped.
Yeah, which makes a point that the mother driver requests a region
that doesn't belong to it. You need to split that properly in the
mother driver and avoid requesting it there. Is it feasible? If not,
why?
...
> > > dev->flags = (uintptr_t)device_get_match_data(&pdev->dev);
> >
> > > + if (!dev->flags)
> >
> > No need to check this. Just define priorities (I would go with above to be
> > higher priority).
> >
> > > + device_property_read_u32(&pdev->dev, "i2c-dw-flags", &dev->flags);
> >
> > Needs to be added to the Device Tree bindings I believe.
> >
> > But wait, don't we have other ways to detect your hardware at probe time and
> > initialize flags respectively?
>
> I2C is connected to our NIC chip with no PCI ID, so I register a platform device for it.
> Please see the 4/9 patch. Software nodes are used to pass the device structure but
> no DT and ACPI. I haven't found another way to initialize flags yet, other than the
> platform data used in the previous patch (it seems to be an obsolete way).
You can share a common data structure between the mother driver and
her children. In that case you may access it via
`dev_get_drvdata(pdev.dev->parent)` call.
OTOH, the property, if only Linux (kernel) specific for internal
usage, should be named accordingly, or be prepared to have one in
Device Tree / ACPI / etc. Examples: USB dwc3 driver (see "linux,"
ones), or intel-lpss-pci.c/intel-lpss-acpi.c (see the SPI type).
--
With Best Regards,
Andy Shevchenko
