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

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Message-ID:
 <OS8PR06MB75418A889FF9E2FF4851DB4CF21CA@OS8PR06MB7541.apcprd06.prod.outlook.com>
Date: Wed, 24 Sep 2025 05:27:50 +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 2/2] usb: ehci: Add Aspeed AST2700 support

> Subject: Re: [PATCH 2/2] usb: ehci: Add Aspeed AST2700 support
> 
> On Thu, Sep 18, 2025 at 02:49:19PM +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 | 26 +++++++++++++++++++++-----
> >  1 file changed, 21 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/usb/host/ehci-platform.c
> > b/drivers/usb/host/ehci-platform.c
> > index 6aab45c8525c..edf1fb4033c2 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>
> > @@ -122,10 +123,18 @@ static const struct ehci_driver_overrides
> platform_overrides __initconst = {
> >  	.extra_priv_size =	sizeof(struct ehci_platform_priv),
> >  };
> >
> > +#define EHCI_PDATA_COMMON        \
> > +	.power_on		= ehci_platform_power_on,	\
> > +	.power_suspend	= ehci_platform_power_off,	\
> > +	.power_off		= ehci_platform_power_off
> > +
> >  static struct usb_ehci_pdata ehci_platform_defaults = {
> > -	.power_on =		ehci_platform_power_on,
> > -	.power_suspend =	ehci_platform_power_off,
> > -	.power_off =		ehci_platform_power_off,
> > +	EHCI_PDATA_COMMON,
> > +};
> > +
> > +static const struct usb_ehci_pdata ehci_ast2700_platform = {
> > +	EHCI_PDATA_COMMON,
> > +	.dma_mask_64 = 1,
> >  };
> 
> Arggh!  This is dreadful.  Just have two copies of the initializers.
> 
> Better yet, change your of_match data into a boolean property for overriding
> the default DMA mask and then use the original ehci_platform_defaults
> structure.  Look at ohci_platform_probe() in ohci-platform.c for an example.
> 
Sorry, I may not see the implement on ohci probe.
https://github.com/torvalds/linux/blob/master/drivers/usb/host/ohci-platform.c#L100-L111
But I think I will modify by following.

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;

err = dma_coerce_mask_and_coherent(&dev->dev,
        dma64 ? DMA_BIT_MASK(64) : DMA_BIT_MASK(32));

and 
+ { .compatible = "aspeed,ast2700-ehci", .data = (void *)1 },

Thanks.

> >
> >  /**
> > @@ -239,6 +248,7 @@ 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;
> > @@ -250,7 +260,10 @@ static int ehci_platform_probe(struct
> platform_device *dev)
> >  	 * Use reasonable defaults so platforms don't have to provide these
> >  	 * with DT probing on ARM.
> >  	 */
> > -	if (!pdata)
> > +	match = of_match_device(dev->dev.driver->of_match_table, &dev->dev);
> > +	if (match && match->data)
> > +		pdata = (struct usb_ehci_pdata *)match->data;
> 
> Do you really want the of_match data to override the platform data?
> Consider a system that has both.  Which one do you think would be more
> important?
> 
> (If you take my suggestion above, this question becomes moot.)
> 
> Alan Stern
> 
> > +	else if (!pdata)
> >  		pdata = &ehci_platform_defaults;
> >
> >  	err = dma_coerce_mask_and_coherent(&dev->dev,
> > @@ -298,7 +311,9 @@ 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 +500,7 @@ 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 = &ehci_ast2700_platform },
> >  	{}
> >  };
> >  MODULE_DEVICE_TABLE(of, vt8500_ehci_ids);
> > --
> > 2.34.1
> >