linux-kernel - RE: [PATCH v2 2/2] usb: ehci: Add Aspeed AST2700 support

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Message-ID:
 <PS1PPF63C81D79D349C89DFE6D73F74B1EFF218A@PS1PPF63C81D79D.apcprd06.prod.outlook.com>
Date: Sun, 28 Sep 2025 02:54:52 +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>, "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 v2 2/2] usb: ehci: Add Aspeed AST2700 support

> Subject: Re: [PATCH v2 2/2] usb: ehci: Add Aspeed AST2700 support
> 
> On Fri, Sep 26, 2025 at 10:33:08AM +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@...eedtech.com>
> > ---
> >  drivers/usb/host/ehci-platform.c | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/host/ehci-platform.c
> > b/drivers/usb/host/ehci-platform.c
> > index 6aab45c8525c..18e231d345d0 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>
> > @@ -239,6 +240,7 @@ 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;
> > @@ -253,6 +255,10 @@ static int ehci_platform_probe(struct
> platform_device *dev)
> >  	if (!pdata)
> >  		pdata = &ehci_platform_defaults;
> >
> > +	match = of_match_device(dev->dev.driver->of_match_table, &dev->dev);
> > +	if (match && match->data)
> > +		pdata->dma_mask_64 = 1;
> 
> You must not do this, since pdata may be pointing to the static
> ehci_platform_defaults structure.  Instead, set a local variable to the value of
> pdata->dma_mask_64, and if match->data is set then update the local
> variable.
> 
> > +
> >  	err = dma_coerce_mask_and_coherent(&dev->dev,
> >  		pdata->dma_mask_64 ? DMA_BIT_MASK(64) : DMA_BIT_MASK(32));
> 
> Then use the local variable here to select which DMA mask is used.
> 
> Alan Stern
Thanks, I will modify by following.

if (!pdata)
    pdata = &ehci_platform_defaults;

match = of_match_device(dev->dev.driver->of_match_table, &dev->dev);

bool dma_mask_64 = pdata->dma_mask_64;
if (match && match->data)
    dma_mask_64 = true;

err = dma_coerce_mask_and_coherent(&dev->dev,
    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;
}