Re: [PATCH 1/1] xhci: add USB2 test mode support

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Wed, Feb 08, 2017 at 11:26:35AM +0100, Alexander Stein wrote:
> This patch adds support for USB2 test mode (Test_J, Test_K,
> Test_SE0_NAK and Test_Packet) per XHCI spec 4.19.6.

What does that mean "in English"?  In other words, why do we want this?
What does it provide for a user?  Why do we care?



> 
> Signed-off-by: "Wang, Yu" <yu.y.wang@intel.com>
> Signed-off-by: "Li, Guanglei" <guangleix.li@intel.com>
> Signed-off-by: "Wu, Hao" <hao.wu@intel.com>
> Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
> ---
> This patch was taken from https://github.com/01org/ProductionKernelQuilts/blob/master/uefi/cht-m1stable/patches/0001-xhci-add-USB2-test-mode-support.patch
> A major difference is that now a xhci_command has to be allocated manually.
> 
>  drivers/usb/host/xhci-hub.c | 63 ++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 62 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> index 0ef1690..cd561f1 100644
> --- a/drivers/usb/host/xhci-hub.c
> +++ b/drivers/usb/host/xhci-hub.c
> @@ -879,13 +879,14 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
>  	int max_ports;
>  	unsigned long flags;
>  	u32 temp, status;
> -	int retval = 0;
> +	int i, retval = 0;
>  	__le32 __iomem **port_array;
>  	int slot_id;
>  	struct xhci_bus_state *bus_state;
>  	u16 link_state = 0;
>  	u16 wake_mask = 0;
>  	u16 timeout = 0;
> +	u16 selector = 0;
>  
>  	max_ports = xhci_get_ports(hcd, &port_array);
>  	bus_state = &xhci->bus_state[hcd_index(hcd)];
> @@ -959,6 +960,8 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
>  			link_state = (wIndex & 0xff00) >> 3;
>  		if (wValue == USB_PORT_FEAT_REMOTE_WAKE_MASK)
>  			wake_mask = wIndex & 0xff00;
> +		if (wValue == USB_PORT_FEAT_TEST)
> +			selector = (wIndex & 0xff00) >> 8;
>  		/* The MSB of wIndex is the U1/U2 timeout */
>  		timeout = (wIndex & 0xff00) >> 8;
>  		wIndex &= 0xff;
> @@ -1134,6 +1137,64 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
>  			temp |= PORT_U2_TIMEOUT(timeout);
>  			writel(temp, port_array[wIndex] + PORTPMSC);
>  			break;
> +		case USB_PORT_FEAT_TEST:
> +			/* 4.19.6 Port Test Modes (USB2 Test Mode) */
> +			if (hcd->speed != HCD_USB2)
> +				goto error;
> +
> +			/* FIXME: Test_Force_Enable case to be implemented */
> +			if (selector < TEST_J || selector > TEST_PACKET)
> +				goto error;
> +
> +			/* Disable all Device Slots */
> +			for (i = 0; i < MAX_HC_SLOTS; i++) {
> +				struct xhci_command *command;
> +
> +				if (!xhci->dcbaa->dev_context_ptrs[i])
> +					continue;
> +				command = xhci_alloc_command(xhci, false,
> +						false, GFP_ATOMIC);
> +				if (!command)
> +					return -ENOMEM;
> +				if (xhci_queue_slot_control(xhci, command,
> +						TRB_DISABLE_SLOT, i)) {
> +					xhci_err(xhci,
> +						"Disable slot[%d] fail!\n", i);
> +						goto error;
> +					}
> +				xhci_dbg(xhci, "Disable Slot[%d].\n", i);
> +			}
> +
> +			/* Put all ports to the Disable state by clear PP */
> +			xhci_dbg(xhci, "Disable all port (PP = 0)\n");
> +			for (i = 0; i < max_ports; i++) {
> +				temp = readl(port_array[i]);
> +				temp &= ~PORT_POWER;
> +				writel(temp, port_array[i]);
> +			}
> +
> +			/* Stop the controller */
> +			xhci_dbg(xhci, "Stop controller\n");
> +			temp = readl(&xhci->op_regs->command);
> +			temp &= ~CMD_RUN;
> +			writel(temp, &xhci->op_regs->command);
> +
> +			if (xhci_handshake(&xhci->op_regs->status,
> +				STS_HALT, STS_HALT, XHCI_MAX_HALT_USEC)) {
> +				xhci_warn(xhci, "Stop controller timeout\n");
> +				return -ETIMEDOUT;
> +			}
> +
> +			/* Disable runtime PM for test mode */
> +			pm_runtime_forbid(hcd->self.controller);
> +
> +			/* Set PORTPMSC.PTC field for selected test mode */
> +			xhci_dbg(xhci, "Enter Test Mode: %d\n", selector);
> +			temp = readl(port_array[wIndex] + PORTPMSC);
> +			temp |= selector << 28;
> +			writel(temp, port_array[wIndex] + PORTPMSC);
> +
> +			break;

What does this "test mode" do?  Where does it report the information?
Who can use it?

thanks,

greg k-h