linux-kernel - Re: [PATCH 2/2] usb: host: pci_quirks: Force hard reset of Renesas uPD72020x USB controller

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Date:   Mon, 17 Jul 2017 15:02:58 +0300
From:   Mathias Nyman <mathias.nyman@...el.com>
To:     Marc Zyngier <marc.zyngier@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [PATCH 2/2] usb: host: pci_quirks: Force hard reset of Renesas
 uPD72020x USB controller

On 10.07.2017 18:52, Marc Zyngier wrote:
> The Renesas uPD72020x XHCI controller seems to suffer from a
> really annoying bug, where it may retain some of its DMA programming
> across a XHCI reset, and despite the driver correctly programming new
> DMA addresses. This is visible if the device has been using 64bit DMA
> addresses, and is then switched to using 32bit DMA addresses. The top
> 32bits of the address (now zero) are ignored are replaced by the 32bit
> from the *previous* programming. Sticking with 64bit DMA always works,
> but doesn't seem very appropriate.
>
> A PCI reset of the device restores the normal functionnality, which
> is done at probe time. Unfortunately, this has to be done before
> any quirk has been discovered, hence the intrusive nature of the fix.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>   drivers/usb/host/pci-quirks.c | 20 ++++++++++++++++++++
>   drivers/usb/host/pci-quirks.h |  1 +
>   drivers/usb/host/xhci-pci.c   |  7 +++++++
>   3 files changed, 28 insertions(+)
>

Acked-by: Mathias Nyman <mathias.nyman@...ux.intel.com>