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

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Message-ID: <0a12f3ac-2600-4ede-a738-f4ab43ad4bee@rowland.harvard.edu>
Date: Sun, 28 Sep 2025 11:29:19 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Ryan Chen <ryan_chen@...eedtech.com>
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,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
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

> +	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
>