linux-kernel - Re: [PATCH v2 4/4] usb: dwc3: Add support for Agilex5 in dwc3-generic-platform driver

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Message-ID: <20251209223127.GA1242261-robh@kernel.org>
Date: Tue, 9 Dec 2025 16:31:27 -0600
From: Rob Herring <robh@...nel.org>
To: adrianhoyin.ng@...era.com
Cc: gregkh@...uxfoundation.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	dinguyen@...nel.org, Thinh.Nguyen@...opsys.com,
	devicetree@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] usb: dwc3: Add support for Agilex5 in
 dwc3-generic-platform driver

On Tue, Dec 09, 2025 at 02:25:11PM +0800, adrianhoyin.ng@...era.com wrote:
> From: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
> 
> Adds support for Agilex5 in the dwc3-generic-platform driver. Extends
> generic driver to support configurable driver data to enable dwc3 core
> property configuration from glue driver.
> 
> Agilex5 DWC3 wrapper has a 40-bit DMA address bus limitation. When SMMU
> is enabled, using the default 64-bit DMA mask can cause DMA addresses to
> be truncated, leading to translation faults.
> 
> This patch adds a `dma_addressable_bits` field in struct dwc3, allowing
> the glue driver to set a 40-bit DMA mask during probe.
> 
> Signed-off-by: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
> ---
>  drivers/usb/dwc3/core.c              |  6 +++++-
>  drivers/usb/dwc3/core.h              |  5 +++++
>  drivers/usb/dwc3/dwc3-generic-plat.c | 20 +++++++++++++++++++-
>  3 files changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index ae140c356295..1fca55637844 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -2243,7 +2243,11 @@ int dwc3_core_probe(const struct dwc3_probe_data *data)
>  
>  	if (!dwc->sysdev_is_parent &&
>  	    DWC3_GHWPARAMS0_AWIDTH(dwc->hwparams.hwparams0) == 64) {
> -		ret = dma_set_mask_and_coherent(dwc->sysdev, DMA_BIT_MASK(64));
> +		if (!dwc->dma_addressable_bits)
> +			dwc->dma_addressable_bits = 64;
> +
> +		ret = dma_set_mask_and_coherent(dwc->sysdev,
> +						DMA_BIT_MASK(dwc->dma_addressable_bits));
>  		if (ret)
>  			goto err_disable_clks;
>  	}
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index a5fc92c4ffa3..a09800fe6577 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -1180,6 +1180,10 @@ struct dwc3_glue_ops {
>   * @wakeup_pending_funcs: Indicates whether any interface has requested for
>   *			 function wakeup in bitmap format where bit position
>   *			 represents interface_id.
> + * @dma_addressable_bits: The number of address bits the device can drive on
> + *			the DMA bus. The driver uses this value to program DMA masks and
> + *			ensure DMA buffers are allocated within the device’s reachable
> + *			address space.
>   */
>  struct dwc3 {
>  	struct work_struct	drd_work;
> @@ -1414,6 +1418,7 @@ struct dwc3 {
>  	struct dentry		*debug_root;
>  	u32			gsbuscfg0_reqinfo;
>  	u32			wakeup_pending_funcs;
> +	u32			dma_addressable_bits;
>  };
>  
>  #define INCRX_BURST_MODE 0
> diff --git a/drivers/usb/dwc3/dwc3-generic-plat.c b/drivers/usb/dwc3/dwc3-generic-plat.c
> index d96b20570002..e9650df6cf81 100644
> --- a/drivers/usb/dwc3/dwc3-generic-plat.c
> +++ b/drivers/usb/dwc3/dwc3-generic-plat.c
> @@ -20,6 +20,11 @@ struct dwc3_generic {
>  	struct reset_control	*resets;
>  };
>  
> +struct dwc3_generic_config {
> +	u32 flags;
> +};
> +
> +#define DWC3_HAS_40BIT_DMA_QUIRK BIT(0)

Quirk flags are good, but if we have 10 different address sizes that's 
10 flags. Just make a dma_addressable_bits field here too, and then it 
is just a straight assignment.

Rob