[PATCH 1/2] usb: xhci: add relaxed timing quirk bit

[Adam Wallis]

On 11/21/2017 3:06 PM, Rob Herring wrote:

[..]

>> 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"?
> 
> Is that for the same thing? If so, drop the vendor prefix and use
> that. Otherwise, a separate property should really be something that
> is per board rather than per SoC.

I don't think that's exactly the same property, but it's the same idea I would
prefer to go with. That way, an integer can be passed in via the firmware tables.

> 
>> If you mean this, where do you recommend I store the
>> desired IRQ_CONTROL value - in struct xhci_hcd ?
> 
> No idea.
> 
>> 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.
> 
> ACPI has match tables too?
> 

Yes, you can use DSD in a way that is similar to OF properties

> It would only be hardcoded per compatible which should be per SoC. Do
> you need per board/device tuning? If so, use a property.
> 

The reason why I think it should dynamic via firmware tables is that

* It's much less invasive for vendors to update their DT tables if they need to
adjust on a per device/controller/family/etc basis then to adjust a properties
table in xhci-plat
* This would lead to less polluting in xhci-plat code

> Rob
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I will provide an updated proposed patch sometime this week. I also hope to get
some feedback from Mathias to see what he prefers.

Thanks again for the feedback Rob.


-- 
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.