From: Roger Quadros <rogerq@ti.com>
To: Arnd Bergmann <arnd@arndb.de>, <linux-arm-kernel@lists.infradead.org>
Cc: Alan Stern <stern@rowland.harvard.edu>,
Felipe Balbi <balbi@kernel.org>,
Grygorii Strashko <grygorii.strashko@ti.com>,
Stuart Yoder <stuart.yoder@nxp.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
Sekhar Nori <nsekhar@ti.com>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
lkml <linux-kernel@vger.kernel.org>,
Scott Wood <oss@buserror.net>,
David Fisher <david.fisher1@synopsys.com>,
"Thang Q. Nguyen" <tqnguyen@apm.com>, Leo Li <pku.leo@gmail.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] usb: dwc3: host: inherit dma configuration from parent dev
Date: Wed, 7 Sep 2016 10:17:31 +0300 [thread overview]
Message-ID: <340685cd-7f06-21db-94cb-a87d0df36286@ti.com> (raw)
In-Reply-To: <5147808.apZTAZ3VPE@wuerfel>
Hi Arnd,
On 02/09/16 18:51, Arnd Bergmann wrote:
> On Friday, September 2, 2016 10:21:23 AM CEST Alan Stern wrote:
>> On Fri, 2 Sep 2016, Felipe Balbi wrote:
>>
>>> Hi,
>>>
>>> Russell King - ARM Linux <linux@armlinux.org.uk> writes:
>>>> On Fri, Sep 02, 2016 at 12:43:39PM +0200, Arnd Bergmann wrote:
>>>>> On Thursday, September 1, 2016 5:14:28 PM CEST Leo Li wrote:
>>>>>>
>>>>>> Hi Felipe and Arnd,
>>>>>>
>>>>>> It has been a while since the last response to this discussion, but we
>>>>>> haven't reached an agreement yet! Can we get to a conclusion on if it
>>>>>> is valid to create child platform device for abstraction purpose? If
>>>>>> yes, can this child device do DMA by itself?
>>>>>
>>>>> I'd say it's no problem for a driver to create child devices in order
>>>>> to represent different aspects of a device, but you should not rely on
>>>>> those devices working when used with the dma-mapping interfaces.
>>>>
>>>> That's absolutely right. Consider the USB model - only the USB host
>>>> controller can perform DMA, not the USB devices themselves. All DMA
>>>> mappings need to be mapped using the USB host controller device struct
>>>> not the USB device struct.
>>>>
>>>> The same _should_ be true everywhere else: the struct device representing
>>>> the device performing DMA must be the one used to map the transfer.
>>>
>>> How do we fix dwc3 in dual-role, then?
>>>
>>> Peripheral-side dwc3 is easy, we just require a glue-layer to be present
>>> and use dwc3.ko's parent device (which will be the PCI device or OF
>>> device). But for host side dwc3, the problem is slightly more complex
>>> because we're using xhci-plat.ko by just instantiating a xhci-platform
>>> device so xhci-plat can probe.
>>>
>>> xhci core has no means to know if its own device or the parent of its
>>> parent should be used for DMA. Any ideas?
>>
>> In theory, you can store a flag somewhere in the platform device,
>> something that would tell xhci-hcd that it has to use the parent's
>> parent for DMA purposes.
>>
>> I know it would be somewhat of a hack, but ought to work.
>
> Speaking of that flag, I suppose we need the same logic to know where
> to look for USB devices attached to a dwc3 host when we need to describe
> them in DT. By default we look for child device nodes under the
> node of the HCD device node, but that would be wrong here too.
I didn't get this part. Information about USB devices attached to a USB host
is never provided in DT because they are always dynamically created via
usb_new_device(), whether they are hard-wired on the board or hot-plugged.
These USB devices inherit their DMA masks in the usb_alloc_dev() routine
whereas each interface within the USB device inherits its DMA mask in
usb_set_configuration().
There is a bug in the USB core because of which the ISB device and interfaces
do not inherit dma_pfn_offset correctly for which I've sent a patch
https://lkml.org/lkml/2016/8/17/275
cheers,
-roger
next prev parent reply other threads:[~2016-09-07 7:18 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-25 19:21 [PATCH] usb: dwc3: host: inherit dma configuration from parent dev Grygorii Strashko
2016-04-26 6:17 ` Felipe Balbi
2016-04-26 8:14 ` Grygorii Strashko
2016-04-27 5:41 ` Felipe Balbi
2016-04-27 11:55 ` Grygorii Strashko
2016-04-27 13:59 ` Catalin Marinas
2016-04-27 14:11 ` Arnd Bergmann
2016-04-27 15:50 ` Catalin Marinas
2016-04-27 16:04 ` Arnd Bergmann
2016-04-27 16:53 ` Felipe Balbi
2016-04-27 17:42 ` Arnd Bergmann
2016-04-27 17:59 ` Alan Stern
2016-04-27 18:08 ` Arnd Bergmann
2016-04-27 20:05 ` Felipe Balbi
2016-04-27 21:05 ` Arnd Bergmann
2016-04-28 6:37 ` Felipe Balbi
2016-04-28 14:16 ` Russell King - ARM Linux
2016-04-28 14:23 ` Arnd Bergmann
2016-04-28 14:27 ` Felipe Balbi
2016-09-01 22:14 ` Leo Li
2016-09-02 10:43 ` Arnd Bergmann
2016-09-02 10:47 ` Russell King - ARM Linux
2016-09-02 11:08 ` Felipe Balbi
2016-09-02 14:11 ` Felipe Balbi
2016-09-02 14:21 ` Alan Stern
2016-09-02 15:51 ` Arnd Bergmann
2016-09-07 7:17 ` Roger Quadros [this message]
2016-09-07 8:29 ` Arnd Bergmann
2016-09-07 13:04 ` Roger Quadros
2016-09-07 14:38 ` Arnd Bergmann
2016-09-02 16:23 ` Grygorii Strashko
2016-09-02 10:53 ` Felipe Balbi
2016-09-02 11:55 ` Robin Murphy
2016-09-02 12:56 ` Felipe Balbi
2016-09-02 13:10 ` Arnd Bergmann
2016-09-02 22:16 ` Leo Li
2016-09-05 15:39 ` Arnd Bergmann
2016-09-06 6:35 ` Peter Chen
2016-09-06 6:40 ` Felipe Balbi
2016-09-06 10:46 ` Arnd Bergmann
2016-09-06 10:50 ` Felipe Balbi
2016-09-06 13:27 ` Arnd Bergmann
2016-09-07 6:51 ` Felipe Balbi
2016-09-07 7:44 ` Peter Chen
2016-09-07 8:52 ` Arnd Bergmann
2016-09-07 9:29 ` Peter Chen
2016-09-07 9:35 ` Russell King - ARM Linux
2016-09-07 10:18 ` Felipe Balbi
2016-09-06 10:38 ` Arnd Bergmann
2016-09-07 6:33 ` Peter Chen
2016-09-07 8:48 ` Arnd Bergmann
2016-09-07 9:55 ` Peter Chen
2016-09-07 10:33 ` Robin Murphy
2016-09-07 10:47 ` Felipe Balbi
2016-09-14 16:31 ` Lorenzo Pieralisi
2016-09-14 21:50 ` Arnd Bergmann
2016-09-07 10:24 ` Felipe Balbi
2016-09-07 15:24 ` Arnd Bergmann
2016-09-07 16:08 ` Alan Stern
2016-09-07 19:45 ` Arnd Bergmann
2016-09-08 1:15 ` Peter Chen
2016-09-08 8:02 ` Arnd Bergmann
2016-09-08 8:03 ` Felipe Balbi
2016-09-08 8:26 ` Arnd Bergmann
2016-09-08 8:29 ` Felipe Balbi
2016-09-08 8:45 ` Arnd Bergmann
2016-09-08 9:43 ` Felipe Balbi
2016-09-08 10:17 ` Arnd Bergmann
2016-09-08 11:00 ` Felipe Balbi
2016-09-08 11:11 ` Arnd Bergmann
2016-09-08 11:20 ` Felipe Balbi
2016-09-08 11:39 ` Arnd Bergmann
2016-09-08 11:52 ` Felipe Balbi
2016-09-08 12:46 ` Arnd Bergmann
2016-09-08 12:02 ` Grygorii Strashko
2016-09-08 12:14 ` Arnd Bergmann
2016-09-08 12:28 ` Peter Chen
2016-09-08 12:52 ` Arnd Bergmann
2016-09-09 1:37 ` Peter Chen
2016-09-08 12:59 ` Grygorii Strashko
2016-09-09 1:52 ` Peter Chen
2016-09-21 11:06 ` Sriram Dash
2016-09-21 11:31 ` Arnd Bergmann
2016-09-21 11:43 ` Sriram Dash
2016-09-21 12:48 ` Arnd Bergmann
2016-09-22 5:02 ` Sriram Dash
2016-10-07 22:46 ` Leo Li
2016-09-21 17:14 ` [PATCH] usb: xhci: Fix the patch inherit dma configuration from kbuild test robot
2016-04-27 20:57 ` [PATCH] usb: dwc3: host: inherit dma configuration from parent dev Felipe Balbi
2016-04-27 14:14 ` Grygorii Strashko
2016-05-05 17:07 ` Brian Norris
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