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

Alan Stern
2025-09-28T15:29:24Z

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@aspeedtech.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
>