linux-kernel - Re: [PATCH v2 2/2] phy: add NXP PTN3222 eUSB2 to USB2 redriver

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Message-ID: <237865a2-61fb-4d05-a57d-261710aad821@quicinc.com>
Date: Fri, 6 Sep 2024 16:40:18 +0800
From: Song Xue <quic_songxue@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        <linux-phy@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        Neil
 Armstrong <neil.armstrong@...aro.org>
Subject: Re: [PATCH v2 2/2] phy: add NXP PTN3222 eUSB2 to USB2 redriver



On 8/31/2024 7:45 AM, Dmitry Baryshkov wrote:
> On Sat, 31 Aug 2024 at 02:13, Song Xue <quic_songxue@...cinc.com> wrote:
>> On 8/30/2024 4:20 PM, Dmitry Baryshkov wrote:
>>> The NXP PTN3222 is the single-port eUSB2 to USB2 redriver that performs
>>> translation between eUSB2 and USB2 signalling schemes. It supports all
>>> three data rates: Low Speed, Full Speed and High Speed.
>>>
>>> The reset state enables autonegotiation of the PHY role and of the data
>>> rate, so no additional programming is required.
>>>
>>> Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>
>>> Tested-by: Konrad Dybcio <konradybcio@...nel.org>
>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>>> ---
>>>    drivers/phy/Kconfig           |  11 ++++
>>>    drivers/phy/Makefile          |   1 +
>>>    drivers/phy/phy-nxp-ptn3222.c | 123 ++++++++++++++++++++++++++++++++++++++++++
>>>    3 files changed, 135 insertions(+)
> 
> [trimmed]
> 
>>> +
>>> +MODULE_DESCRIPTION("NXP PTN3222 eUSB2 Redriver driver");
>>> +MODULE_LICENSE("GPL");
>>>
>> The I2C driver just realizes the function on reset and PWR. What about
>> other I2C driver function like I2C interface operations,
> 
> I don't quite understand what you mean by this. Could you please clarify?
> 
>>   auto-suspend,
> 
> I think you mean pm_runtime here. It's a valid case, but granted that
> it should stay enabled when USB controller is enabled, the gain should
> be pretty limited. I'll consider a followup patch implementing
> pm_runtime for the sake of being able to disable I2C host if DWC3
> controller disables the PHY.
> 
>> remote wakeup,
> 
> Not supported by design. PTN3222 doesn't have IRQ pins to report
> events to the host.
> 
>> memory maps etc.
> 
> huh?
> 
>>   Who will enable these? I think it is not
>> incomplete I2C driver, if on someday, ptn3222 is used as I2C device.
> 
> Well, I'm using it as an I2C device.
> 
Sorry for the delayed response.
The functions I listed, such as auto-suspend and wake-up, are just 
examples. My main point is that a basic I2C driver should include 
fundamental functions like setting up the I2C bus, configuring the 
clock, and setting the SDA (data line) and SCL (clock line). A basic I2C 
driver shouldn’t be limited to enabling the power supply and reset pin, 
as these features can be handled by other drivers as well.
If you implement these fundamental functions, I think it will be sufficient.

Regards,
Song Xue