Message-ID: <8737irvkt5.fsf@linux.intel.com>
Date:   Wed, 16 Nov 2016 11:24:54 +0200
From:   Felipe Balbi <felipe.balbi@...ux.intel.com>
To:     John Youn <John.Youn@...opsys.com>,
        Christian Lamparter <chunkeey@...glemail.com>,
        John Youn <John.Youn@...opsys.com>
Cc:     "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree\@vger.kernel.org" <devicetree@...r.kernel.org>,
        "linux-usb\@vger.kernel.org" <linux-usb@...r.kernel.org>,
        "linuxppc-dev\@lists.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 1/2] usb: dwc2: add amcc,dwc-otg support


Hi, 

John Youn <John.Youn@...opsys.com> writes:
> On 11/14/2016 3:00 PM, John Youn wrote:
>> On 11/11/2016 3:12 PM, Christian Lamparter wrote:
>>> On Friday, November 11, 2016 2:20:42 PM CET John Youn wrote:
>>>> On 11/11/2016 2:05 PM, Christian Lamparter wrote:
>>>>> On Friday, November 11, 2016 1:22:16 PM CET John Youn wrote:
>>>>>> On 11/11/2016 12:59 PM, Christian Lamparter wrote:
>>>>>>> This patch adds support for the "amcc,usb-otg" device
>>>>>>> which is found in the PowerPC Canyonlands' dts.
>>>>>>>
>>>>>>> The device definition was added by:
>>>>>>> commit c89b3458d8cc ("powerpc/44x: Add USB DWC DTS entry to Canyonlands board")'
>>>>>>> but without any driver support as the dwc2 driver wasn't
>>>>>>> available at that time.
>>>>>>>
>>>>>>> Note: The system can't use the generic "snps,dwc2" compatible
>>>>>>> because of the special ahbcfg configuration. The default
>>>>>>> GAHBCFG_HBSTLEN_INCR4 of snps,dwc2 can cause a system hang
>>>>>>> when the USB and SATA is used concurrently.
>>>>>>
>>>>>> I don't want to add any more of these param structures to the driver
>>>>>> unless really necessary. We're trying to remove usage of them in favor
>>>>>> of using auto-detected defaults and device properties to override
>>>>>> them.
>>>>> Ok, thanks. I think that would work. I've attached an updated patch.
>>>>> Can it be applied/queued now? Or do you want me to resent it later?
>>>>>
>>>>>> The AHB Burst is actually one of the ones we were going to do next
>>>>>> because our platform also doesn't work well with INCR4. In fact I'm
>>>>>> thinking of making the default INCR.
>>>>> Is that actually possible to change the default still? This would
>>>>> require to re-evaluate all existing archs/platforms that use 
>>>>> "snps,dwc2" for INCR16 compatibility. 
>>>>
>>>> INCR, not INCR16, but you're right, so we may not change it even
>>>> though though INCR is usually the right choice over INCR4.
>>> What about making a device-tree property?
>> 
>> Yes, that's what I meant. I'll send a change for this shortly.
>> 
>>>
>>> Recommended properties:
>>>  - g-ahb-bursts : specifies the ahb bursts length, should be one of
>>>    "single", "INCRx", "INCR4", "INCR8", or "INCR16". If not specified
>>>    the safer but inefficient "INCR4" is used. The optimal setting is
>>>    "INCRx".
>>>
>>> Would this work? If so, I can make a patch over the weekend.
>>>> Anyways, with the binding, can't you just set the compatible string to
>>>> snps,dwc2?
>>>
>>> Ah, let me explain. I had a discussion with Mark Rutland and Rob Herring
>>> a while back about device-tree bindings.
>>>
>>> They made it very clear to me, that they don't want any generic "catch all
>>> compatible" strings:
>>>
>>> "Bindings should be for hardware (either specific device models, or for
>>> classes), and not for Linux drivers. The latter is subject to arbitrary
>>> changes while the former is not, as old hardware continues to exist and
>>> does not change while drivers get completely reworked." [0]
>>>
>>> Furthermore, this is an existing binding in kernel's canyonlands.dts [1]
>>> and this binding can't be easily changed. Rob Herring explained this in
>>> the context of the "basic-mmio-gpio" patch [2] when I was editing the dts
>>> to make them work with the changes I made:
>>>
>>> "You can't remove the old drivers as they are needed to work with 
>>> old dtbs, so there is no gain.
>>>
>>> You would need to match on existing compatibles such as
>>> moxa,moxart-gpio and provide a match data struct that has all the info
>>> you are adding here (e.g. data register offset). Then additionally you
>>> could add "basic-mmio-gpio" (I would drop "basic" part) and the
>>> additional data associated with it. But it has to be new properties,
>>> not changing properties. Changing the reg values doesn't work."
>>>
>>> So, for this to work with the existing canyonlands.dts, I need to have
>>> the "amcc,dwc-otg" compatible string.
>> 
>> Ok, if that's the case. But still a bit confused as to what driver was
>> working with it before since the binding was not defined for dwc2.
>> 
>>>
>>> Of course, it would be great to hear from Rob Herring and/or Mark Rutland
>>> about this case.
>>>
>>> Regards,
>>> Christian
>>>
>>> [0] <https://patchwork.kernel.org/patch/8976221/>
>>> [1] <http://lxr.free-electrons.com/source/arch/powerpc/boot/dts/canyonlands.dts#L181>
>>> [2] <http://www.spinics.net/lists/devicetree/msg124538.html>
>>>
>>>  
>>>>>
>>>>> From what I can tell based would be:
>>>>> bcm11351, bcm21664, bcm23550, exynos3250, stm32f429, rk3xxx,
>>>>> stratix10, meson-gxbb, rt3050 and some Altera FPGAs.
>>>>>
>>>>>> If that's all you need then a devicetree binding should be enough
>>>>>> right?
>>>>> Yes. The device is working fine so far.
>>>>>
>>>>> Regards,
>>>>> Christian
>>>>>
>>>>> ---
>>>>> From 70dd4be016b89655a56bc8260f04683b50f07644 Mon Sep 17 00:00:00 2001
>>>>> From: Christian Lamparter <chunkeey@...il.com>
>>>>> Date: Sun, 6 Nov 2016 00:39:24 +0100
>>>>> Subject: [PATCH] usb: dwc2: add amcc,dwc-otg support
>>>>>
>>>>> This patch adds support for the "amcc,usb-otg" device
>>>>> which is found in the PowerPC Canyonlands' dts.
>>>>>
>>>>> The device definition was added by:
>>>>> commit c89b3458d8cc ("powerpc/44x: Add USB DWC DTS entry to Canyonlands board")'
>>>>> but without any driver support as the dwc2 driver wasn't
>>>>> available at that time.
>>>>>
>>>>> Note: The system can't use the generic "snps,dwc2" compatible
>>>>> because of the special ahbcfg configuration. The default
>>>>> GAHBCFG_HBSTLEN_INCR4 of snps,dwc2 can cause a system hang
>>>>> when the USB and SATA is used concurrently.
>>>>>
>>>>> Cc: Felipe Balbi <felipe.balbi@...ux.intel.com>
>>>>> Cc: John Youn <johnyoun@...opsys.com>
>>>>> Signed-off-by: Christian Lamparter <chunkeey@...il.com>
>>>>> ---
>>>>> v1->v2:
>>>>> 	- moved definitons to params.c
>>>>> 	- removed dma_enable / host_dma parameter
>>>>> 	- added dma_desc_fs_enable parameter
>>>>> v2->v3:
>>>>> 	- removed parameters
>>>>>
>>>>> Please queue this patch until GAHBCFG_HBSTLEN_INCR16 is the default
>>>>> for ahbcfg.
>>>>> ---
>>>>>  Documentation/devicetree/bindings/usb/dwc2.txt | 1 +
>>>>>  drivers/usb/dwc2/params.c                      | 1 +
>>>>>  2 files changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/usb/dwc2.txt b/Documentation/devicetree/bindings/usb/dwc2.txt
>>>>> index 10a2a4b..6ccfe85 100644
>>>>> --- a/Documentation/devicetree/bindings/usb/dwc2.txt
>>>>> +++ b/Documentation/devicetree/bindings/usb/dwc2.txt
>>>>> @@ -12,6 +12,7 @@ Required properties:
>>>>>    - "lantiq,xrx200-usb": The DWC2 USB controller instance in Lantiq XRX SoCs;
>>>>>    - "amlogic,meson8b-usb": The DWC2 USB controller instance in Amlogic Meson8b SoCs;
>>>>>    - "amlogic,meson-gxbb-usb": The DWC2 USB controller instance in Amlogic S905 SoCs;
>>>>> +  - "amcc,dwc-otg": The DWC2 USB controller instance in AMCC Canyonlands 460EX SoCs;
>>>>>    - snps,dwc2: A generic DWC2 USB controller with default parameters.
>>>>>  - reg : Should contain 1 register range (address and length)
>>>>>  - interrupts : Should contain 1 interrupt
>>>>> diff --git a/drivers/usb/dwc2/params.c b/drivers/usb/dwc2/params.c
>>>>> index 64d5c66..9506ab0 100644
>>>>> --- a/drivers/usb/dwc2/params.c
>>>>> +++ b/drivers/usb/dwc2/params.c
>>>>> @@ -239,6 +239,7 @@ const struct of_device_id dwc2_of_match_table[] = {
>>>>>  	{ .compatible = "samsung,s3c6400-hsotg", .data = NULL},
>>>>>  	{ .compatible = "amlogic,meson8b-usb", .data = &params_amlogic },
>>>>>  	{ .compatible = "amlogic,meson-gxbb-usb", .data = &params_amlogic },
>>>>> +	{ .compatible = "amcc,dwc-otg", .data = NULL },
>>>>>  	{},
>>>>>  };
>>>>>  MODULE_DEVICE_TABLE(of, dwc2_of_match_table);
>>>>>
>> 
>> For dwc2 part:
>> 
>> Acked-by: John Youn <johnyoun@...opsys.com>
>> 
>
> Hi Felipe,
>
> Can you drop this from your testing/next?
>
> I meant for the 2nd version to be applied, without the params
> structure.
>
> I can send you a clean version to apply later today.

done

-- 
balbi

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