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

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Message-ID:
 <KUZSPRMB0005CC6A87F6FFC5A08F12BFF21BA@KUZSPRMB0005.apcprd06.prod.outlook.com>
Date: Mon, 29 Sep 2025 05:56:13 +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 v3 2/2] usb: ehci: Add Aspeed AST2700 support

> 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@...eedtech.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
> >