On Mon, Dec 04, 2017 at 09:27:51AM -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-ns", 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.
>
> Tested-by: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>
> Signed-off-by: Adam Wallis <awallis@xxxxxxxxxxxxxx>
> ---
> changes from v3:
> * Changed imod-interval to imod-interval-ns [Rob Herring/Chunfeng]
> * Changed "modulation" to "moderation" throughout patch [Mathias]
> 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 | 5 +++++
> drivers/usb/host/xhci.c | 7 ++-----
> drivers/usb/host/xhci.h | 2 ++
> 7 files changed, 24 insertions(+), 5 deletions(-)
Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
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