[PATCH v2] usb: xhci: allow imod-interval to be configurable

[Chunfeng Yun]

Hi,
On Wed, 2017-11-29 at 10:52 -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.
> 
> Backwards compatibility is maintained for MTK_HOSTS through the quirk
> bit, however, imod_interval should be pushed into device tree at a
> future point and this quirk should be removed from xhci_plat_probe
> 
> Signed-off-by: Adam Wallis <awallis at codeaurora.org>
> ---
> 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/usb-xhci.txt |  1 +
>  drivers/usb/host/xhci-plat.c                       | 13 +++++++++++++
>  drivers/usb/host/xhci.c                            |  7 ++-----
>  drivers/usb/host/xhci.h                            |  2 ++
>  4 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt b/Documentation/devicetree/bindings/usb/usb-xhci.txt
> index ae6e484..3998459 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: IMOD_INTERVAL in nano-seconds. Default is 40000
>  
>  Example:
>  	usb at f0931000 {
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index 09f164f..3c63de1 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -23,6 +23,7 @@
>  #include "xhci-plat.h"
>  #include "xhci-mvebu.h"
>  #include "xhci-rcar.h"
> +#include "xhci-mtk.h"
Needn't it, MTK makes use of xhci-mtk.c but not xhci-plat.c

>  
>  static struct hc_driver __read_mostly xhci_plat_hc_driver;
>  
> @@ -269,6 +270,18 @@ 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.
> +	 * The increment interval is 8 times as much as that defined in
> +	 * the xHCI spec on MTK's controller. This quirk check exists to provide
> +	 * backwards compatibility, however, this should be pushed into
> +	 * the device tree files at some point in the future and
> +	 * checking the quirk should be removed from xhci_plat_probe.
> +	 */
> +	xhci->imod_interval = xhci->quirks & XHCI_MTK_HOST ? 5000 : 40000;
Can be moved into xhci-mtk.c for MTK quirk, like as following:

diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
index 2d473e0..a03451b 100644
--- a/drivers/usb/host/xhci-mtk.c
+++ b/drivers/usb/host/xhci-mtk.c
@@ -699,6 +699,13 @@ static int xhci_mtk_probe(struct platform_device *pdev)
                goto power_off_phys;
        }

+       /*
+        * the increment interval is 8 times as much as that defined
+        * in xHCI spec on MTK's controller
+        */
+ 	xhci->imod_interval = 5000;
+       device_property_read_u32(dev, "imod-interval", &xhci->imod_interval);
+
        ret = usb_add_hcd(hcd, irq, IRQF_SHARED);
        if (ret)
                goto put_usb3_hcd;

Thanks

> +
> +	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;