linux-kernel - Re: [PATCH 3/3] usb: cdns3: Enable workaround for USB2.0 PHY Rx compliance test PHY lockup

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Date:   Wed, 26 Aug 2020 15:49:57 +0300
From:   Roger Quadros <rogerq@...com>
To:     Peter Chen <peter.chen@....com>,
        Pawel Laszczak <pawell@...ence.com>
CC:     "balbi@...nel.org" <balbi@...nel.org>,
        Rahul Kumar <kurahul@...ence.com>,
        "nsekhar@...com" <nsekhar@...com>,
        "vigneshr@...com" <vigneshr@...com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 3/3] usb: cdns3: Enable workaround for USB2.0 PHY Rx
 compliance test PHY lockup

Peter,

On 26/08/2020 11:07, Peter Chen wrote:
>   
>>
>>
>>>
>>> On 20-08-26 04:04:01, Pawel Laszczak wrote:
>>>>> On 20-08-25 15:00:59, Roger Quadros wrote:
>>>>>> From: Pawel Laszczak <pawell@...ence.com>
>>>>>>
>>>>>> USB2.0 PHY hangs in Rx Compliance test when the incoming packet
>>>>>> amplitude is varied below and above the Squelch Level of Receiver
>>>>>> during the active packet multiple times.
>>>>>>
>>>>>> Version 1 of the controller allows PHY to be reset when RX fail
>>>>>> condition is detected to work around the above issue. This feature
>>>>>> is disabled by default and needs to be enabled using a bit from
>>>>>> the newly added PHYRST_CFG register. This patch enables the workaround.
>>>>>>
>>>>>> As there is no way to distinguish between the controller version
>>>>>> before the device controller is started we need to rely on a DT
>>>>>> property to decide when to apply the workaround.
>>>>>
>>>>> Pawel, it could know the controller version at cdns3_gadget_start,
>>>>> but the controller starts when it tries to bind gadget driver, at
>>>>> that time, it has already known the controller version.
>>>>>
>>>>> For me, the device controller starts is using USB_CONF.DEVEN (Device
>>>>> Enable) through usb_gadget_connect, I am not sure if it is the same
>>>>> with yours.
>>>>>
>>>>
>>>> Yes in device mode driver knows controller version but this
>>>> workaround Must be enabled also in host mode. In host mode the
>>>> controller doesn't have access to device registers. The controller
>>>> version is placed in device register.
>>>>
>>>
>>> You may suggest your design team adding CHIP_VER register at global
>>> register region, it will easy the software engineer life.
>>>
>> >From what I read, this register is only enabling USB2 PHY reset
>>> software control, it needs for all chips with rev 0x0002450D, and the
>>> place you current change is only for 0x0002450D, right?
>>
>> Even I could say that this workaround should be enabled only for Specific USB2
>> PHY  (only 0x0002450D)
>>
>> This bit should not have any impact for Cadence PHY but it can has Impact for third
>> party PHYs.
>>
> 
> So, it is related to specific PHY, but enable this specific PHY reset bit is at controller region, why don't
> put this enable bit at PHY region?

I think this is related to Controller + PHY combination.
The fix for the issue is via a bit in the controller, so it needs to be managed by the
controller driver.

> 
> So, you use controller's device property to know this specific PHY, can controller know this specific
> PHY dynamically?

Still the PHY will have to tell the controller the enable that bit. How to do that?

Adding a dt-property that vendors can used was the simplest option.

cheers,
-roger

> 
> Peter
> 
>> Pawel
>>
>>>
>>> Peter
>>>
>>>> Pawel
>>>>
>>>>> Peter
>>>>>
>>>>>
>>>>>>
>>>>>> Signed-off-by: Pawel Laszczak <pawell@...ence.com>
>>>>>> Signed-off-by: Roger Quadros <rogerq@...com>
>>>>>> ---
>>>>>>   drivers/usb/cdns3/core.c |  2 ++
>>>>>>   drivers/usb/cdns3/core.h |  1 +
>>>>>>   drivers/usb/cdns3/drd.c  | 12 ++++++++++++
>>>>>> drivers/usb/cdns3/drd.h  |  5 ++++-
>>>>>>   4 files changed, 19 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
>>>>>> index 5c1586ec7824..34b36487682b 100644
>>>>>> --- a/drivers/usb/cdns3/core.c
>>>>>> +++ b/drivers/usb/cdns3/core.c
>>>>>> @@ -443,6 +443,8 @@ static int cdns3_probe(struct platform_device *pdev)
>>>>>>   		return -ENXIO;
>>>>>>   	}
>>>>>>
>>>>>> +	cdns->phyrst_a_enable = device_property_read_bool(dev,
>>>>>> +"cdns,phyrst-a-enable");
>>>>>> +
>>>>>>   	cdns->otg_res = *res;
>>>>>>
>>>>>>   	mutex_init(&cdns->mutex);
>>>>>> diff --git a/drivers/usb/cdns3/core.h b/drivers/usb/cdns3/core.h
>>>>>> index 1ad1f1fe61e9..24cf0f1b5726 100644
>>>>>> --- a/drivers/usb/cdns3/core.h
>>>>>> +++ b/drivers/usb/cdns3/core.h
>>>>>> @@ -76,6 +76,7 @@ struct cdns3 {
>>>>>>   #define CDNS3_CONTROLLER_V0	0
>>>>>>   #define CDNS3_CONTROLLER_V1	1
>>>>>>   	u32				version;
>>>>>> +	bool				phyrst_a_enable;
>>>>>>
>>>>>>   	int				otg_irq;
>>>>>>   	int				dev_irq;
>>>>>> diff --git a/drivers/usb/cdns3/drd.c b/drivers/usb/cdns3/drd.c
>>>>>> index 6234bcd6158a..b74803e9703d 100644
>>>>>> --- a/drivers/usb/cdns3/drd.c
>>>>>> +++ b/drivers/usb/cdns3/drd.c
>>>>>> @@ -42,6 +42,18 @@ int cdns3_set_mode(struct cdns3 *cdns, enum
>> usb_dr_mode mode)
>>>>>>   			reg = readl(&cdns->otg_v1_regs->override);
>>>>>>   			reg |= OVERRIDE_IDPULLUP;
>>>>>>   			writel(reg, &cdns->otg_v1_regs->override);
>>>>>> +
>>>>>> +			/*
>>>>>> +			 * Enable work around feature built into the
>>>>>> +			 * controller to address issue with RX Sensitivity
>>>>>> +			 * est (EL_17) for USB2 PHY. The issue only occures
>>>>>> +			 * for 0x0002450D controller version.
>>>>>> +			 */
>>>>>> +			if (cdns->phyrst_a_enable) {
>>>>>> +				reg = readl(&cdns->otg_v1_regs->phyrst_cfg);
>>>>>> +				reg |= PHYRST_CFG_PHYRST_A_ENABLE;
>>>>>> +				writel(reg, &cdns->otg_v1_regs->phyrst_cfg);
>>>>>> +			}
>>>>>>   		} else {
>>>>>>   			reg = readl(&cdns->otg_v0_regs->ctrl1);
>>>>>>   			reg |= OVERRIDE_IDPULLUP_V0;
>>>>>> diff --git a/drivers/usb/cdns3/drd.h b/drivers/usb/cdns3/drd.h
>>>>>> index 7e7cf7fa2dd3..f1ccae285a16 100644
>>>>>> --- a/drivers/usb/cdns3/drd.h
>>>>>> +++ b/drivers/usb/cdns3/drd.h
>>>>>> @@ -31,7 +31,7 @@ struct cdns3_otg_regs {
>>>>>>   	__le32 simulate;
>>>>>>   	__le32 override;
>>>>>>   	__le32 susp_ctrl;
>>>>>> -	__le32 reserved4;
>>>>>> +	__le32 phyrst_cfg;
>>>>>>   	__le32 anasts;
>>>>>>   	__le32 adp_ramp_time;
>>>>>>   	__le32 ctrl1;
>>>>>> @@ -153,6 +153,9 @@ struct cdns3_otg_common_regs {
>>>>>>   /* Only for CDNS3_CONTROLLER_V0 version */
>>>>>>   #define OVERRIDE_IDPULLUP_V0		BIT(24)
>>>>>>
>>>>>> +/* PHYRST_CFG - bitmasks */
>>>>>> +#define PHYRST_CFG_PHYRST_A_ENABLE     BIT(0)
>>>>>> +
>>>>>>   #define CDNS3_ID_PERIPHERAL		1
>>>>>>   #define CDNS3_ID_HOST			0
>>>>>>
>>>>>> --
>>>>>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>>>>>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>>>>>>
>>>>>
>>>>> --
>>>>>
>>>>> Thanks,
>>>>> Peter Chen
>>>
>>> --
>>>
>>> Thanks,
>>> Peter Chen

-- 
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki