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Subject: Re: [PATCH 2/2] usb-storage: revert from scsi_add_host_with_dma() to
 scsi_add_host()
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Tom Yan <tom.ty89@gmail.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Christoph Hellwig <hch@lst.de>,
        linux-usb <linux-usb@vger.kernel.org>,
        Mathias Nyman <mathias.nyman@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-pci@vger.kernel.org, Lu Baolu <baolu.lu@linux.intel.com>
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From:   Hans de Goede <hdegoede@redhat.com>
Message-ID: <70ca74c2-4a80-e25b-eca9-a63a75516673@redhat.com>
Date:   Mon, 30 Nov 2020 14:55:45 +0100
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Hi,

On 11/30/20 2:53 PM, Greg KH wrote:
> On Mon, Nov 30, 2020 at 02:36:38PM +0100, Hans de Goede wrote:
>> Hi,
>>
>> On 11/30/20 2:30 PM, Greg KH wrote:
>>> On Mon, Nov 30, 2020 at 02:23:48PM +0100, Hans de Goede wrote:
>>>> Hi,
>>>>
>>>> On 11/30/20 1:58 PM, Tom Yan wrote:
>>>>> It's merely a moving of comment moving for/and a no-behavioral-change
>>>>> adaptation for the reversion.>
>>>>
>>>> IMHO the revert of the troublesome commit and the other/new changes really
>>>> should be 2 separate commits. But I will let Alan and Greg have the final
>>>> verdict on this.
>>>
>>> I would prefer to just revert the commits and not do anything
>>> different/special here so late in the release cycle.
>>>
>>> So, if Alan agrees, I'll be glad to do them on my end, I just need the
>>> commit ids for them.
>>
>> The troublesome commit are (in reverse, so revert, order):
>>
>> 5df7ef7d32fe ("uas: bump hw_max_sectors to 2048 blocks for SS or faster drives")
>> 558033c2828f ("uas: fix sdev->host->dma_dev")
>> 0154012f8018 ("usb-storage: fix sdev->host->dma_dev")
>>
>> Alan, the reason for reverting these is that using scsi_add_host_with_dma() as the
>> last 2 patches do, with the dmadev argument of that call pointing to the device
>> for the XHCI controller is causing changes to the DMA settings of the XHCI controller
>> itself which is causing regressions in 5.10, see this email thread:
>>
>> https://lore.kernel.org/linux-usb/fde7e11f-5dfc-8348-c134-a21cb1116285@redhat.com/T/#t
> 
> Thanks, I'll wait for Alan to respond, but I think just reverting these
> is the best solution at this point in time.  You have tested those
> reverts, solve this, right?  If so, can I get a "Tested-by:"? 

Yes that was my first solution to this problem and I can confirm that that fixes
the regression:

Tested-by: Hans de Goede <hdegoede@redhat.com>

Regards,

Hans