Re: [PATCH 2/2] usb: ehci: Add Aspeed AST2700 support

[Alan Stern <stern@rowland.harvard.edu>]

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@aspeedtech.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.

>  
>  /**
> @@ -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
>