linux-kernel - Re: [PATCH 2/3] xhci: Add zhaoxin xHCI U1/U2 feature support

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Date:   Thu, 20 Apr 2023 17:07:16 +0300
From:   Mathias Nyman <mathias.nyman@...el.com>
To:     Weitao Wang <WeitaoWang-oc@...oxin.com>,
        gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     tonywwang@...oxin.com, weitaowang@...oxin.com
Subject: Re: [PATCH 2/3] xhci: Add zhaoxin xHCI U1/U2 feature support

On 20.4.2023 20.21, Weitao Wang wrote:
> Add U1/U2 feature support of xHCI for zhaoxin.
> 
> Signed-off-by: Weitao Wang <WeitaoWang-oc@...oxin.com>
> ---
>   drivers/usb/host/xhci-pci.c |  5 +++++
>   drivers/usb/host/xhci.c     | 27 +++++++++++++++++++++++++--
>   2 files changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
> index 6db07ca419c3..a235effe8e5c 100644
> --- a/drivers/usb/host/xhci-pci.c
> +++ b/drivers/usb/host/xhci-pci.c
> @@ -334,6 +334,11 @@ static void xhci_pci_quirks(struct device *dev, struct xhci_hcd *xhci)
>   	     pdev->device == PCI_DEVICE_ID_AMD_PROMONTORYA_4))
>   		xhci->quirks |= XHCI_NO_SOFT_RETRY;
>   
> +	if (pdev->vendor == PCI_VENDOR_ID_ZHAOXIN) {
> +		xhci->quirks |= XHCI_LPM_SUPPORT;
> +		xhci->quirks |= XHCI_ZHAOXIN_HOST;
> +	}
> +
>   	/* xHC spec requires PCI devices to support D3hot and D3cold */
>   	if (xhci->hci_version >= 0x120)
>   		xhci->quirks |= XHCI_DEFAULT_PM_RUNTIME_ALLOW;
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 6307bae9cddf..730c0f68518d 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -4802,7 +4802,7 @@ static u16 xhci_calculate_u1_timeout(struct xhci_hcd *xhci,
>   		}
>   	}
>   
> -	if (xhci->quirks & XHCI_INTEL_HOST)
> +	if (xhci->quirks & (XHCI_INTEL_HOST | XHCI_ZHAOXIN_HOST))
>   		timeout_ns = xhci_calculate_intel_u1_timeout(udev, desc);

Looks odd to tie Zhaoxin vendor to Intel specific values but ok,
if they diverge in the future we anyway need to modify this.

>   	else
>   		timeout_ns = udev->u1_params.sel;
> @@ -4866,7 +4866,7 @@ static u16 xhci_calculate_u2_timeout(struct xhci_hcd *xhci,
>   		}
>   	}
>   
> -	if (xhci->quirks & XHCI_INTEL_HOST)
> +	if (xhci->quirks & (XHCI_INTEL_HOST | XHCI_ZHAOXIN_HOST))
>   		timeout_ns = xhci_calculate_intel_u2_timeout(udev, desc);

same.

>   	else
>   		timeout_ns = udev->u2_params.sel;
> @@ -4938,6 +4938,27 @@ static int xhci_update_timeout_for_interface(struct xhci_hcd *xhci,
>   	return 0;
>   }
>   
> +static int xhci_check_zhaoxin_tier_policy(struct usb_device *udev,
> +		enum usb3_link_state state)
> +{
> +	struct usb_device *parent;
> +	unsigned int num_hubs;
> +
> +	/* Don't enable U1/U2 if the device is on an external hub. */
> +	for (parent = udev->parent, num_hubs = 0; parent->parent;
> +			parent = parent->parent)
> +		num_hubs++;
> +
> +	if (num_hubs < 1)
> +		return 0;
> +
> +	dev_dbg(&udev->dev, "Disabling U1/U2 link state for device"
> +			" below external hub.\n");
> +	dev_dbg(&udev->dev, "Plug device into root hub "
> +			"to decrease power consumption.\n");
> +	return -E2BIG;
> +}
> +

I don't think we should add more vendor specific functions, this is almost
an exact copy of xhci_check_intel_tier_policy().

How about getting rid of both of those and use something like this instead (untested):

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 2b280beb0011..e9a25e4d99cf 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4926,10 +4926,24 @@ static int xhci_check_tier_policy(struct xhci_hcd *xhci,
                 struct usb_device *udev,
                 enum usb3_link_state state)
  {
-       if (xhci->quirks & XHCI_INTEL_HOST)
-               return xhci_check_intel_tier_policy(udev, state);
-       else
-               return 0;
+       struct usb_device *parent = udev->parent;
+       int tier = 1; /* roothub is tier1 */
+
+       while (parent) {
+               parent = parent->parent;
+               tier++;
+       }
+
+       if (xhci->quirks & XHCI_INTEL_HOST && tier > 3)
+               goto fail;
+       if (xhci->quirks & XHCI_ZHAOXIN_HOST && tier > 2)
+               goto fail;
+
+       return 0;
+fail:
+       dev_dbg(&udev->dev, "Tier policy prevents U1/U2 LPM states for devices at tier %d\n",
+               tier);
+       return -E2BIG;
  }

Or possibly even add a xhci->max_tier_for_lpm that can be set during probe based on
vendor or from device property.

Thanks
-Mathias