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Date:   Fri, 13 May 2022 12:47:49 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Thorsten Leemhuis <regressions@leemhuis.info>
Cc:     Christoph Hellwig <hch@lst.de>, linux-usb@vger.kernel.org,
        bugzilla-daemon@kernel.org,
        "regressions@lists.linux.dev" <regressions@lists.linux.dev>,
        "open list:HID CORE LAYER" <linux-input@vger.kernel.org>,
        Satadru Pramanik <satadru@umich.edu>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Henrik Rydberg <rydberg@bitmath.org>
Subject: Re: [Bug 215890] New: Regression in 5.18: bcm5974 trackpad causes
 error: xhci_hcd rejecting DMA map of vmalloc memory
Message-ID: <20220513104749.GA2634@lst.de>
References: <bug-215890-208809@https.bugzilla.kernel.org/> <76e24afa-ad7d-bf6d-d610-df61851b3e2b@leemhuis.info> <8365ac4b-c45a-dbff-eed1-8ccc88a8d02f@leemhuis.info> <20220513103724.GA2289@lst.de>
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On Fri, May 13, 2022 at 12:37:24PM +0200, Christoph Hellwig wrote:
> > #regzbot introduced: f5ff79fddf0efecca538046b5cc20fb3ded2
> 
> Well, this just uncovered an existing bug in the driver.  You can not
> just dma map memory returned from dma_alloc_coherent, and this driver
> would already get vmalloc memory on arm/arm64 platforms anyway, we
> now just do the same on x86 as well.

>From a quick look through the trace it seems somehow
usb_hcd_map_urb_for_dma tries to create another DMA mapping for a buffer
allocated from usb_alloc_coherent that uses a dma coherent allocation
below.  It really needs to use the dma address returned from
usb_alloc_coherent instead of trying to map the URB again.  But I don't
have the slightest idea of why that only happens for this particular
setup, and I really need some helpe from the usb folks to untangle it