RE: [PATCH v3 4/4] usb: uhci: Add Aspeed AST2700 support

[Ryan Chen]

> Subject: Re: [PATCH v3 4/4] usb: uhci: Add Aspeed AST2700 support
> 
> On Fri, Sep 19, 2025 at 10:57:12AM +0800, Ryan Chen wrote:
> > Unlike earlier Aspeed SoCs (AST2400/2500/2600) which are limited to
> > 32-bit DMA addressing, the UHCI controller in AST2700 supports 64-bit
> > DMA. Update the platform UHCI driver to select the appropriate DMA
> > mask based on the device tree compatible string.
> >
> > Signed-off-by: Ryan Chen <ryan_chen@xxxxxxxxxxxxxx>
> > ---
> >  drivers/usb/host/uhci-platform.c | 15 +++++++++++----
> >  1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/usb/host/uhci-platform.c
> > b/drivers/usb/host/uhci-platform.c
> > index f255358d6242..5b4be9a5764a 100644
> > --- a/drivers/usb/host/uhci-platform.c
> > +++ b/drivers/usb/host/uhci-platform.c
> > @@ -71,6 +71,7 @@ static int uhci_hcd_platform_probe(struct
> platform_device *pdev)
> >  	struct usb_hcd *hcd;
> >  	struct uhci_hcd	*uhci;
> >  	struct resource *res;
> > +	u64 *dma_mask_ptr;
> >  	int ret;
> >
> >  	if (usb_disabled())
> > @@ -81,7 +82,8 @@ static int uhci_hcd_platform_probe(struct
> platform_device *pdev)
> >  	 * Since shared usb code relies on it, set it here for now.
> >  	 * Once we have dma capability bindings this can go away.
> >  	 */
> > -	ret = dma_coerce_mask_and_coherent(&pdev->dev,
> DMA_BIT_MASK(32));
> > +	dma_mask_ptr = (u64 *)of_device_get_match_data(&pdev->dev);
> > +	ret = dma_coerce_mask_and_coherent(&pdev->dev, *dma_mask_ptr);
> 
> What will happen here if of_device_get_match_data() returns 0 or an error?
> Shouldn't you test for that and then use dma_mask_32 as the default mask?


I'll update the code to fall back to a 32-bit DMA mask in that case
dma_mask_ptr = of_device_get_match_data(&pdev->dev);
if (!dma_mask_ptr)
    dma_mask_ptr = &dma_mask_32;

ret = dma_coerce_mask_and_coherent(&pdev->dev, *dma_mask_ptr);


> 
> And if you do this then do you need to add the .data fields to the existing
> entries in the platform_uhci_ids table below?

I've added .data = &dma_mask_32 for the existing generic-uhci 
and platform-uhci entries so they also work correctly with this logic.

 +	{ .compatible = "generic-uhci", .data = &dma_mask_32},
 +	{ .compatible = "platform-uhci", .data = &dma_mask_32},
 +	{ .compatible = "aspeed,ast2700-uhci", .data = &dma_mask_64},

> 
> Alan Stern
> 
> >  	if (ret)
> >  		return ret;
> >
> > @@ -114,7 +116,8 @@ static int uhci_hcd_platform_probe(struct
> platform_device *pdev)
> >  		}
> >  		if (of_device_is_compatible(np, "aspeed,ast2400-uhci") ||
> >  		    of_device_is_compatible(np, "aspeed,ast2500-uhci") ||
> > -		    of_device_is_compatible(np, "aspeed,ast2600-uhci")) {
> > +		    of_device_is_compatible(np, "aspeed,ast2600-uhci") ||
> > +		    of_device_is_compatible(np, "aspeed,ast2700-uhci")) {
> >  			uhci->is_aspeed = 1;
> >  			dev_info(&pdev->dev,
> >  				 "Enabled Aspeed implementation workarounds\n"); @@
> -189,9
> > +192,13 @@ static void uhci_hcd_platform_shutdown(struct
> platform_device *op)
> >  	uhci_hc_died(hcd_to_uhci(hcd));
> >  }
> >
> > +static const u64 dma_mask_32 =	DMA_BIT_MASK(32);
> > +static const u64 dma_mask_64 =	DMA_BIT_MASK(64);
> > +
> >  static const struct of_device_id platform_uhci_ids[] = {
> > -	{ .compatible = "generic-uhci", },
> > -	{ .compatible = "platform-uhci", },
> > +	{ .compatible = "generic-uhci", .data = &dma_mask_32},
> > +	{ .compatible = "platform-uhci", .data = &dma_mask_32},
> > +	{ .compatible = "aspeed,ast2700-uhci", .data = &dma_mask_64},
> >  	{}
> >  };
> >  MODULE_DEVICE_TABLE(of, platform_uhci_ids);
> > --
> > 2.34.1
> >