RE: [PATCH v3 2/2] usb: ehci: Add Aspeed AST2700 support

Ryan Chen
2025-09-29T05:56:18Z

> Subject: Re: [PATCH v3 2/2] usb: ehci: Add Aspeed AST2700 support
>
> On Sun, Sep 28, 2025 at 11:24:07AM +0800, Ryan Chen wrote:
> > Unlike earlier Aspeed SoCs (AST2400/2500/2600) which are limited to
> > 32-bit DMA addressing, the EHCI controller in AST2700 supports 64-bit
> > DMA. Update the EHCI platform driver to make use of this capability by
> > selecting a 64-bit DMA mask when the "aspeed,ast2700-ehci" compatible
> > is present in device tree.
> >
> > Signed-off-by: Ryan Chen <ryan_chen@aspeedtech.com>
> > ---
>
> This is basically good and it can be merged. However...
>
> > drivers/usb/host/ehci-platform.c | 15 +++++++++++++--
> > 1 file changed, 13 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/usb/host/ehci-platform.c
> > b/drivers/usb/host/ehci-platform.c
> > index 6aab45c8525c..bcd1c9073515 100644
> > --- a/drivers/usb/host/ehci-platform.c
> > +++ b/drivers/usb/host/ehci-platform.c
> > @@ -27,6 +27,7 @@
> > #include <linux/io.h>
> > #include <linux/module.h>
> > #include <linux/of.h>
> > +#include <linux/of_device.h>
> > #include <linux/platform_device.h>
> > #include <linux/reset.h>
> > #include <linux/sys_soc.h>
> > @@ -239,9 +240,11 @@ static int ehci_platform_probe(struct
> platform_device *dev)
> > struct usb_hcd *hcd;
> > struct resource *res_mem;
> > struct usb_ehci_pdata *pdata = dev_get_platdata(&dev->dev);
> > + const struct of_device_id *match;
> > struct ehci_platform_priv *priv;
> > struct ehci_hcd *ehci;
> > int err, irq, clk = 0;
> > + bool dma_mask_64;
> >
> > if (usb_disabled())
> > return -ENODEV;
> > @@ -253,8 +256,13 @@ static int ehci_platform_probe(struct
> platform_device *dev)
> > if (!pdata)
> > pdata = &ehci_platform_defaults;
> >
> > + dma_mask_64 = pdata->dma_mask_64;
> > + match = of_match_device(dev->dev.driver->of_match_table, &dev->dev);
>
> (I just noticed this.) The "dev->dev.driver->of_match_table" part looks odd.
> Why not just write "vt8500_ehci_ids"? Do you expect that this could ever
> have a different value?
>
> Alan Stern
Thanks your feedback.
I used dev->dev.driver->of_match_table rather than hard-coding vt8500_ehci_ids
to keep the probe code generic and tied to the driver model, not to a specific symbol.
Functionally it's the same here, but this pattern avoids coupling the probe to a
particular table name.

How you think ?

Ryan.

>
> > + if (match && match->data)
> > + dma_mask_64 = true;
> > +
> > err = dma_coerce_mask_and_coherent(&dev->dev,
> > - pdata->dma_mask_64 ? DMA_BIT_MASK(64) : DMA_BIT_MASK(32));
> > + dma_mask_64 ? DMA_BIT_MASK(64) : DMA_BIT_MASK(32));
> > if (err) {
> > dev_err(&dev->dev, "Error: DMA mask configuration failed\n");
> > return err;
> > @@ -298,7 +306,9 @@ static int ehci_platform_probe(struct
> platform_device *dev)
> > if (of_device_is_compatible(dev->dev.of_node,
> > "aspeed,ast2500-ehci") ||
> > of_device_is_compatible(dev->dev.of_node,
> > - "aspeed,ast2600-ehci"))
> > + "aspeed,ast2600-ehci") ||
> > + of_device_is_compatible(dev->dev.of_node,
> > + "aspeed,ast2700-ehci"))
> > ehci->is_aspeed = 1;
> >
> > if (soc_device_match(quirk_poll_match))
> > @@ -485,6 +495,7 @@ static const struct of_device_id vt8500_ehci_ids[] = {
> > { .compatible = "wm,prizm-ehci", },
> > { .compatible = "generic-ehci", },
> > { .compatible = "cavium,octeon-6335-ehci", },
> > + { .compatible = "aspeed,ast2700-ehci", .data = (void *)1 },
> > {}
> > };
> > MODULE_DEVICE_TABLE(of, vt8500_ehci_ids);
> > --
> > 2.34.1
> >