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

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Message-ID:
 <OS8PR06MB7541A49CB2ADBBA1BC4B3139F212A@OS8PR06MB7541.apcprd06.prod.outlook.com>
Date: Mon, 22 Sep 2025 02:52:25 +0000
From: Ryan Chen <ryan_chen@...eedtech.com>
To: Alan Stern <stern@...land.harvard.edu>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 4/4] usb: uhci: Add Aspeed AST2700 support

> Subject: RE: [PATCH v3 4/4] usb: uhci: Add Aspeed AST2700 support
> 
> > 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@...eedtech.com>
> > > ---
> > >  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},
> 
Sorry, I think I mis-understood your request.
I will update use 32-bit as default.
	dma_mask_ptr = (u64 *)of_device_get_match_data(&pdev->dev);
	if (!dma_mask_ptr)
	    dma_mask_ptr = &dma_mask_32; --> default

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

And only add for aspeed,ast2700-uhci dma_mask_64 in platform_uhci_ids

Thanks a lot.
Ryan

> >
> > 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
> > >