Message-ID: <f9be1906-3d94-e9c6-841a-d7baa2572f75@synopsys.com>
Date:   Mon, 14 Nov 2016 15:00:51 -0800
From:   John Youn <John.Youn@...opsys.com>
To:     Christian Lamparter <chunkeey@...glemail.com>,
        John Youn <John.Youn@...opsys.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>
Subject: Re: [PATCH 1/2] usb: dwc2: add amcc,dwc-otg support

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>

Regards,
John

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