linux-kernel - Re: [PATCH v2] USB: ehci-s5p: Fix phy reset

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Message-Id: <6F88F86A-8C8E-4C2E-BD15-14C788FC6E48@suse.de>
Date:	Thu, 14 Mar 2013 13:01:38 +0100
From:	Alexander Graf <agraf@...e.de>
To:	Thomas Abraham <thomas.abraham@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org, dmueller@...e.de,
	Vivek Gautam <gautam.vivek@...sung.com>,
	Jingoo Han <jg1.han@...sung.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Doug Anderson <dianders@...omium.org>
Subject: Re: [PATCH v2] USB: ehci-s5p: Fix phy reset


On 14.03.2013, at 05:19, Thomas Abraham wrote:

> On 14 March 2013 05:29, Alexander Graf <agraf@...e.de> wrote:
>> On my Exynos 5 based Arndale system, I need to pull the reset line down
>> and then let it go up again to actually perform a reset. Without that
>> reset, I can't find any USB hubs on my bus, rendering the USB controller
>> useless.
>> 
>> We also only need to reset the line after the phy node has been found.
>> This way we don't accidently reserve the vbus GPIO pin, but later on
>> defer the creation of our controller, because the phy device tree node
>> hasn't been probed yet.
>> 
>> This patch implements the above logic, making EHCI and OHCI work on
>> Arndale systems for me.
>> 
>> Signed-off-by: Alexander Graf <agraf@...e.de>
>> CC: Vivek Gautam <gautam.vivek@...sung.com>
>> CC: Jingoo Han <jg1.han@...sung.com>
>> CC: Alan Stern <stern@...land.harvard.edu>
>> CC: Kukjin Kim <kgene.kim@...sung.com>
>> CC: Felipe Balbi <balbi@...com>
>> CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> CC: Doug Anderson <dianders@...omium.org>
>> 
>> ---
>> 
>> v1 -> v2:
>> 
>>  - remove gpio_free call
>>  - move reset logic after phy node search
>> 
>> diff --git a/drivers/usb/host/ehci-s5p.c b/drivers/usb/host/ehci-s5p.c
>> index 20ebf6a..b29b2b8 100644
>> --- a/drivers/usb/host/ehci-s5p.c
>> +++ b/drivers/usb/host/ehci-s5p.c
>> @@ -103,9 +103,14 @@ static void s5p_setup_vbus_gpio(struct platform_device *pdev)
>>        if (!gpio_is_valid(gpio))
>>                return;
>> 
>> -       err = gpio_request_one(gpio, GPIOF_OUT_INIT_HIGH, "ehci_vbus_gpio");
>> -       if (err)
>> +       /* reset pulls the line down, then up again */
>> +       err = gpio_request_one(gpio, GPIOF_OUT_INIT_LOW, "ehci_vbus_gpio");
>> +       if (err) {
>>                dev_err(&pdev->dev, "can't request ehci vbus gpio %d", gpio);
>> +               return;
>> +       }
>> +       mdelay(1);
>> +       __gpio_set_value(gpio, 1);
>> }
>> 
>> static u64 ehci_s5p_dma_mask = DMA_BIT_MASK(32);
>> @@ -131,8 +136,6 @@ static int s5p_ehci_probe(struct platform_device *pdev)
>>        if (!pdev->dev.coherent_dma_mask)
>>                pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
>> 
>> -       s5p_setup_vbus_gpio(pdev);
>> -
>>        s5p_ehci = devm_kzalloc(&pdev->dev, sizeof(struct s5p_ehci_hcd),
>>                                GFP_KERNEL);
>>        if (!s5p_ehci)
>> @@ -152,6 +155,8 @@ static int s5p_ehci_probe(struct platform_device *pdev)
>>                s5p_ehci->otg = phy->otg;
>>        }
>> 
>> +       s5p_setup_vbus_gpio(pdev);
>> +
>>        s5p_ehci->dev = &pdev->dev;
>> 
>>        hcd = usb_create_hcd(&s5p_ehci_hc_driver, &pdev->dev,
> 
> Hi Alexander,
> 
> This change, though it works for Exynos5250 based Arndale board, does
> not actually seem correct. On Arndale board, the on-board 4-port usb
> hub is self powered and hence the vbus 'enable' gpio line from
> Exynos5250 SoC is instead used as a "reset" signal for the on-board
> usb hub (and not as the vbus enable signal).
> 
> Whereas, the driver uses the gpio used in 's5p_setup_vbus_gpio'
> function as just a mechanism to enable vbus for downstream devices. So
> the driver should not be modified as above to handle the board
> specific behavior.
> 
> Instead, what needs to be done is, remove the "samsung,vbus-gpio"
> property from the usb2.0 node in dts files (this property is optional)
> for Arndale board. Then, during the machine_init, perform the reset
> sequencing as required.
> 
> Ideally, the reset sequencing for the on-board AX88760 usb hub should
> have been handled in the driver for this device. I have not checked if
> there is a driver for this in the kernel.

I can see your point, but as I mentioned earlier there seems to be some timing issue here. By simply doing the reset a few ms earlier (in the first probe, before the driver detects that it needs to defer probing), I already can't find the hub on the bus later.

So I'm assuming that the same thing would also happen if I put it even earlier in machine init.

The change in this patch actually does a reset even on non-Arndale boards. By taking away power and returning power to the line, the chip will most likely have reset :). So even on non-Arndale boards, this should get the USB phy into a clean state regardless of where the bootloader left it, right?


Alex

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