linux-kernel - Re: [PATCH v10 1/5] usb: xhci: Change the XHCI link order in the Makefile

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Date:   Wed, 13 May 2020 08:08:07 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Al Cooper <alcooperx@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Alan Stern <stern@...land.harvard.edu>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        bcm-kernel-feedback-list@...adcom.com, devicetree@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-usb@...r.kernel.org, Mathias Nyman <mathias.nyman@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v10 1/5] usb: xhci: Change the XHCI link order in the
 Makefile



On 5/13/2020 5:26 AM, Greg Kroah-Hartman wrote:
> On Tue, May 12, 2020 at 11:00:15AM -0400, Al Cooper wrote:
>> Some BRCMSTB USB chips have an XHCI, EHCI and OHCI controller
>> on the same port where XHCI handles 3.0 devices, EHCI handles 2.0
>> devices and OHCI handles <2.0 devices. Currently the Makefile
>> has XHCI linking at the bottom which will result in the XHIC driver
>> initalizing after the EHCI and OHCI drivers and any installed 3.0
>> device will be seen as a 2.0 device. Moving the XHCI linking
>> above the EHCI and OHCI linking fixes the issue.
> 
> What happens if all of these are modules and they are loaded in a
> different order?  This makefile change will not help with that, you need
> to have logic in the code in order to properly coordinate this type of
> mess, sorry.

I believe we should be using module soft dependencies to instruct the
module loaders to load the modules in the correct order, so something
like this would do (not tested) for xhci-plat-hcd.c:

MODULE_SOFTDEP("post: ehci-hcd ohci-hcd");

and I am not sure whether we need to add the opposite for ehci-hcd and
ohci-hcd:

MODULE_SOFTDEP("pre: xhci-plat-hcd");

Al, do you want to test that?
-- 
Florian