Subject: Re: [PATCH v3 2/2] usb:dwc3: pass arch data to xhci-hcd child
To: Felipe Balbi <felipe.balbi@linux.intel.com>,
        Grygorii Strashko <grygorii.strashko@ti.com>,
        "Thang Q. Nguyen" <tqnguyen@apm.com>
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Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, linux-usb@vger.kernel.org,
        linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm@lists.infradead.org, Arnd Bergmann <arnd@arndb.de>,
        "Karicheri, Muralidharan" <m-karicheri2@ti.com>,
        Peter Ujfalusi <peter.ujfalusi@ti.com>, Phong Vo <pvo@apm.com>,
        Loc Ho <lho@apm.com>, patches <patches@apm.com>,
        Santosh Shilimkar <ssantosh@kernel.org>,
        "Ben Dooks (embedded platforms)" <ben-linux@fluff.org>,
        Russell King <linux@arm.linux.org.uk>
From: santosh shilimkar <santosh.shilimkar@oracle.com>
Organization: Oracle Corporation
Message-ID: <57029232.1080103@oracle.com>
Date: Mon, 4 Apr 2016 09:11:30 -0700
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On 4/3/2016 11:28 PM, Felipe Balbi wrote:
> santosh shilimkar <santosh.shilimkar@oracle.com> writes:
>> +Arnd, RMK,
>>
>> On 4/1/2016 4:57 AM, Felipe Balbi wrote:
>>>
>>> Hi,
>>>
>>> Grygorii Strashko <grygorii.strashko@ti.com> writes:
>>>> On 04/01/2016 01:20 PM, Felipe Balbi wrote:
>>
>> [...]
>>
>>>> commit 7ace8fc8219e4cbbfd5b4790390d9a01a2541cdf
>>>> Author: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
>>>> Date:   Mon Jul 13 18:10:05 2015 +0900
>>>>
>>>>       usb: gadget: udc: core: Fix argument of dma_map_single for IOMMU
>>>>
>>>>       The dma_map_single and dma_unmap_single should set "gadget->dev.parent"
>>>>       instead of "&gadget->dev" in the first argument because the parent has
>>>>       a udc controller's device pointer.
>>>>       Otherwise, iommu functions are not called in ARM environment.
>>>>
>>>>       Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
>>>>       Signed-off-by: Felipe Balbi <balbi@ti.com>
>>>>
>>>> Above actually means that DMA configuration code can be dropped from
>>>> usb_add_gadget_udc_release() completely. Right?:
>>>
>>> true, but now I'm not sure what's better: copy all necessary bits from
>>> parent or just pass the parent device to all DMA API.
>>>
>>> Anybody to shed a light here ?
>>>
>> The expectation is drivers should pass the proper dev pointers and let
>> core DMA code deal with it since it knows the per device dma properties.
>
> okay, so how do you get proper DMA pointers with something like this:
>
> 	kdwc3_dma_mask = dma_get_mask(dev);
> 	dev->dma_mask = &kdwc3_dma_mask;
>
> This doesn't anything.
>
Drivers actually needs to touch dma_mask(s) only if the core DMA
code hasn't populated it it. I see Grygorii pointed out couple
of things already.

Reagrds,
Santosh