On 11/21/2017 2:11 PM, Rob Herring wrote: > On Tue, Nov 21, 2017 at 12:18:09PM -0500, Adam Wallis wrote: >> Certain systems may run with CPUs at a very slow frequency. This >> patch adds a quirk bit that can be used to relax certain timings, etc. >> >> This quirk might be needed for other fields in the future, but >> initially, it will be used only on the IRQ control register to allow >> firmare to control the value of the register. This can prevent an > > s/firmare/firmware/ > Thanks, good catch. > By firmware control, you mean the register is initialized on boot and > then not touched by the kernel? What if the XHCI block is reset? Not > sure if that's possible. > >> "interrupt storm" effect on certain systems. > > So now we have 2 ways to deal with this? The existing MediaTek quirk and > now this one. I do agree that 2 different ways to deal with it is not ideal. I also think that having one hard-coded value (and one alternate for MTK) is also not ideal. > > I think you should change the existing quirk to a value and set the > value based on compatible strings. I like where you are going with this. Are you saying that I could read for a device property read from firmware (for DTB or ACPI) like DWC3 does for "snps,hird-threshold"? If you mean this, where do you recommend I store the desired IRQ_CONTROL value - in struct xhci_hcd ? Or by "compatible" strings, did you mean storing hard-coded values in the of_device_id usb_xhci_of_match[] array? This would still be hard-coding (which I would like to avoid) and also would not work for the ACPI case. > >> Signed-off-by: Adam Wallis <awallis@xxxxxxxxxxxxxx> >> --- >> Documentation/devicetree/bindings/usb/usb-xhci.txt | 1 + >> drivers/usb/host/xhci.c | 25 +++++++++++++++------- >> drivers/usb/host/xhci.h | 1 + >> 3 files changed, 19 insertions(+), 8 deletions(-) Thanks for the feedback Rob. Adam -- Adam Wallis Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
