Re: [PATCH v3] usb: xhci: allow imod-interval to be configurable

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On Fri, 2017-12-01 at 10:44 -0500, Adam Wallis wrote:
> The xHCI driver currently has the IMOD set to 160, which
> translates to an IMOD interval of 40,000ns (160 * 250)ns
> 
> Commit 0cbd4b34cda9 ("xhci: mediatek: support MTK xHCI host controller")
> introduced a QUIRK for the MTK platform to adjust this interval to 20,
> which translates to an IMOD interval of 5,000ns (20 * 250)ns. This is
> due to the fact that the MTK controller IMOD interval is 8 times
> as much as defined in xHCI spec.
> 
> Instead of adding more quirk bits for additional platforms, this patch
> introduces the ability for vendors to set the IMOD_INTERVAL as is
> optimal for their platform. By using device_property_read_u32() on
> "imod-interval", the IMOD INTERVAL can be specified in nano seconds. If
> no interval is specified, the default of 40,000ns (IMOD=160) will be
> used.
> 
> No bounds checking has been implemented due to the fact that a vendor
> may have violated the spec and would need to specify a value outside of
> the max 8,000 IRQs/second limit specified in the xHCI spec.
> 
> Signed-off-by: Adam Wallis <awallis@xxxxxxxxxxxxxx>
> ---
> changes from v2:
>   * Added PCI default value [Mathias]
>   * Removed xhci-mtk.h from xhci-plat.c [Chunfeng Yun]
>   * Removed MTK quirk from xhci-plat and moved logic to xhci-mtk [Chunfeng]
>   * Updated bindings Documentation to use proper units [Rob Herring]
>   * Added imod-interval description and example to MTK binding documentation
> changes from v1:
>   * Removed device_property_read_u32() per suggestion from greg k-h
>   * Used ER_IRQ_INTERVAL_MASK in place of (u16) cast
> 
>  Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.txt | 2 ++
>  Documentation/devicetree/bindings/usb/usb-xhci.txt          | 1 +
>  drivers/usb/host/xhci-mtk.c                                 | 9 +++++++++
>  drivers/usb/host/xhci-pci.c                                 | 3 +++
>  drivers/usb/host/xhci-plat.c                                | 4 ++++
>  drivers/usb/host/xhci.c                                     | 7 ++-----
>  drivers/usb/host/xhci.h                                     | 2 ++
>  7 files changed, 23 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.txt b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.txt
> index 3059596..45bbf18 100644
> --- a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.txt
> +++ b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.txt
> @@ -46,6 +46,7 @@ Optional properties:
>   - pinctrl-names : a pinctrl state named "default" must be defined
>   - pinctrl-0 : pin control group
>  	See: Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
> + - imod-interval: Default interval is 5000ns
I think, as Rob suggested before, recommend to have a unit suffix
appended to the property name.
s/imod-interval/imod-interval-ns
 
>  
>  Example:
>  usb30: usb@11270000 {
> @@ -66,6 +67,7 @@ usb30: usb@11270000 {
>  	usb3-lpm-capable;
>  	mediatek,syscon-wakeup = <&pericfg>;
>  	mediatek,wakeup-src = <1>;
> +	imod-interval = <10000>;
>  };
>  
>  2nd: dual-role mode with xHCI driver
> diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt b/Documentation/devicetree/bindings/usb/usb-xhci.txt
> index ae6e484..89b68f1 100644
> --- a/Documentation/devicetree/bindings/usb/usb-xhci.txt
> +++ b/Documentation/devicetree/bindings/usb/usb-xhci.txt
> @@ -29,6 +29,7 @@ Optional properties:
>    - usb2-lpm-disable: indicate if we don't want to enable USB2 HW LPM
>    - usb3-lpm-capable: determines if platform is USB3 LPM capable
>    - quirk-broken-port-ped: set if the controller has broken port disable mechanism
> +  - imod-interval: Default interval is 40000ns
>  
>  Example:
>  	usb@f0931000 {
> diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
> index b62a1d2..278ea3b 100644
> --- a/drivers/usb/host/xhci-mtk.c
> +++ b/drivers/usb/host/xhci-mtk.c
> @@ -674,6 +674,15 @@ static int xhci_mtk_probe(struct platform_device *pdev)
>  
>  	xhci = hcd_to_xhci(hcd);
>  	xhci->main_hcd = hcd;
> +
> +	/*
> +	 * imod_interval is the interrupt modulation value in nanoseconds.
> +	 * The increment interval is 8 times as much as that defined in
> +	 * the xHCI spec on MTK's controller.
> +	 */
> +	xhci->imod_interval = 5000;
> +	device_property_read_u32(dev, "imod-interval", &xhci->imod_interval);
> +
>  	xhci->shared_hcd = usb_create_shared_hcd(driver, dev,
>  			dev_name(dev), hcd);
>  	if (!xhci->shared_hcd) {
> diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
> index 7ef1274..efbe57b 100644
> --- a/drivers/usb/host/xhci-pci.c
> +++ b/drivers/usb/host/xhci-pci.c
> @@ -234,6 +234,9 @@ static int xhci_pci_setup(struct usb_hcd *hcd)
>  	if (!xhci->sbrn)
>  		pci_read_config_byte(pdev, XHCI_SBRN_OFFSET, &xhci->sbrn);
>  
> +	/* imod_interval is the interrupt modulation value in nanoseconds. */
> +	xhci->imod_interval = 40000;
> +
>  	retval = xhci_gen_setup(hcd, xhci_pci_quirks);
>  	if (retval)
>  		return retval;
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index 09f164f..b78be87 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -269,6 +269,10 @@ static int xhci_plat_probe(struct platform_device *pdev)
>  	if (device_property_read_bool(&pdev->dev, "quirk-broken-port-ped"))
>  		xhci->quirks |= XHCI_BROKEN_PORT_PED;
>  
> +	/* imod_interval is the interrupt modulation value in nanoseconds. */
> +	xhci->imod_interval = 40000;
> +	device_property_read_u32(sysdev, "imod-interval", &xhci->imod_interval);
> +
>  	hcd->usb_phy = devm_usb_get_phy_by_phandle(sysdev, "usb-phy", 0);
>  	if (IS_ERR(hcd->usb_phy)) {
>  		ret = PTR_ERR(hcd->usb_phy);
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 2424d30..0b7755b 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -586,11 +586,8 @@ int xhci_run(struct usb_hcd *hcd)
>  			"// Set the interrupt modulation register");
>  	temp = readl(&xhci->ir_set->irq_control);
>  	temp &= ~ER_IRQ_INTERVAL_MASK;
> -	/*
> -	 * the increment interval is 8 times as much as that defined
> -	 * in xHCI spec on MTK's controller
> -	 */
> -	temp |= (u32) ((xhci->quirks & XHCI_MTK_HOST) ? 20 : 160);
> +	temp |= (xhci->imod_interval / 250) & ER_IRQ_INTERVAL_MASK;
> +
>  	writel(temp, &xhci->ir_set->irq_control);
>  
>  	/* Set the HCD state before we enable the irqs */
> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index 99a014a..2a4177b 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -1717,6 +1717,8 @@ struct xhci_hcd {
>  	u8		max_interrupters;
>  	u8		max_ports;
>  	u8		isoc_threshold;
> +	/* imod_interval in ns (I * 250ns) */
> +	u32		imod_interval;
>  	int		event_ring_max;
>  	/* 4KB min, 128MB max */
>  	int		page_size;


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