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Date:   Sat, 21 Jan 2023 07:39:26 +0530
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Subject: Re: [RFC v4 2/5] usb: dwc3: core: Refactor PHY logic to support
 Multiport Controller
Content-Language: en-US
To:     Thinh Nguyen <Thinh.Nguyen@synopsys.com>
CC:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Felipe Balbi <balbi@kernel.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "quic_pkondeti@quicinc.com" <quic_pkondeti@quicinc.com>,
        "quic_ppratap@quicinc.com" <quic_ppratap@quicinc.com>,
        "quic_wcheng@quicinc.com" <quic_wcheng@quicinc.com>,
        "quic_jackp@quicinc.com" <quic_jackp@quicinc.com>,
        "quic_harshq@quicinc.com" <quic_harshq@quicinc.com>
References: <20230115114146.12628-1-quic_kriskura@quicinc.com>
 <20230115114146.12628-3-quic_kriskura@quicinc.com>
 <20230119003619.ane3weigd4ebsta6@synopsys.com>
 <7fa2d7b0-509d-ae90-4208-6f0245f927f7@quicinc.com>
 <20230120010226.wjwtisj4id6frirl@synopsys.com>
 <91fa86d8-f443-db13-1544-73e2dd50d964@quicinc.com>
 <20230120224400.77t2j3qtcdfqwt5s@synopsys.com>
From:   Krishna Kurapati PSSNV <quic_kriskura@quicinc.com>
In-Reply-To: <20230120224400.77t2j3qtcdfqwt5s@synopsys.com>
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On 1/21/2023 4:14 AM, Thinh Nguyen wrote:
> On Fri, Jan 20, 2023, Krishna Kurapati PSSNV wrote:
>>
>>
>> On 1/20/2023 6:32 AM, Thinh Nguyen wrote:
>>> Hi,
>>>
>>> On Thu, Jan 19, 2023, Krishna Kurapati PSSNV wrote:
>>>>
>>>>
>>>> On 1/19/2023 6:06 AM, Thinh Nguyen wrote:
>>>>> Hi,
>>>>>
>>>>> On Sun, Jan 15, 2023, Krishna Kurapati wrote:
>>>>>> Currently the DWC3 driver supports only single port controller
>>>>>> which requires at most one HS and one SS PHY.
>>>>>
>>>>> Add note here that multi-port is for host mode for clarity.
>>>>>
>>>>>>
>>>>>> But the DWC3 USB controller can be connected to multiple ports and
>>>>>> each port can have their own PHYs. Each port of the multiport
>>>>>> controller can either be HS+SS capable or HS only capable
>>>>>> Proper quantification of them is required to modify GUSB2PHYCFG
>>>>>> and GUSB3PIPECTL registers appropriately.
>>>>>>
>>>>>> Add support for detecting, obtaining and configuring phy's supported
>>>>>> by a multiport controller and limit the max number of ports
>>>>>> supported to 4.
>>>>>>
>>>>>> Signed-off-by: Harsh Agarwal <quic_harshq@quicinc.com>
>>>>>> Signed-off-by: Krishna Kurapati <quic_kriskura@quicinc.com>
>>>>>> ---
>>>>>>     drivers/usb/dwc3/core.c | 304 +++++++++++++++++++++++++++++-----------
>>>>>>     drivers/usb/dwc3/core.h |  15 +-
>>>>>>     drivers/usb/dwc3/drd.c  |  14 +-
>>>>>>     3 files changed, 244 insertions(+), 89 deletions(-)
>>>>>>
>>>
>>> <snip>
>>>
>>>>>> @@ -1575,6 +1690,21 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>>>>>>     	dwc->dis_split_quirk = device_property_read_bool(dev,
>>>>>>     				"snps,dis-split-quirk");
>>>>>> +
>>>>>> +	/*
>>>>>> +	 * If no mulitport properties are defined, default
>>>>>
>>>>> multi*
>>>>>
>>>>>> +	 * the port count to '1'.
>>>>>> +	 */
>>>>>
>>>>> Can we initialize num_ports and num_ss_ports to 1 instead of setting it
>>>>> on error (similar to how we handle other properties).
>>>>>
>>>> Hi Thinh,
>>>>
>>>>     Thanks for the review. On the bindings, Rob and Krzysztof have suggested
>>>> to get the num-ports and num-ss-ports by counting the Phy-names in DT.
>>>
>>> This may be a bit problematic for non-DT device. Currently pci devices
>>> pass fake DT properties to send these kinds of info. But that's fine,
>>> we can enhance dwc3 for non-DT devices later.
>>>
>>>>
>>>> Since there may be many cases where the user might skip giving any Phy's or
>>>> even skip different ports in the DT if he doesn't want to use them, can we
>>>> design/refactor the below logic as follows while mandating the fact that
>>>> user must give the SS Phy's if any starting from Port-0.:
>>>>
>>>> num-ss-ports = max_port_index (usb3-portX) + 1
>>>> num-ports = max (max_port_index(usb2-portX), num-ss-ports) + 1
>>>>
>>>> Ex: If there are 3 ports and only 1 is SS capable and user decides to skip
>>>> port-2 HS Phy.
>>>>
>>>> case-1: phy-names = "usb2-port0", "usb3-port0", "usb2-port-1"
>>>> case-2: phy-names = "usb2-port0", "usb2-port-1", "usb3-port1"
>>>>
>>>> In both cases, only one SS is present, just the order is changed. (Not sure
>>>> if last few ports can be made SS Capable instead of the first ports on any
>>>> HW) ?
>>>>
>>>> But according to the above formula:
>>>>
>>>> In case-1 : (num-ports = 2, num-ss-ports = 1) - This is correct
>>>> In case-2: (num-ports = 2, num-ss-ports = 2) - This is wrong
>>>>
>>>
>>> Can't we just walk through all the phy names to figure that out? Let's
>>> not require the user to specify Port-0 is SS capable if they can skip
>>> it.
>>>
>> Hi Thinh,
>>
>> Thanks for the review.
>>
>>    May be I wasn't able to convey my intention properly in my previous
>> thread. The above suggested method doesn't tell that user must not skip any
>> phy.
>>
>> Let us take the below case for 2 Port (HS+SS) capable controller.
>> If the user skips ss-phy 2, then:
>>
>> phy-names = "usb2-port0", "usb3-port0", "usb2-port-1"
>>
>> We don't need to configure GUSB3PIPECTL2 (for port-2) register ere. If we
>> parse phy-names and find it out, we see there are 2 hs-phy's and 1-ssphy and
>> num-ports = 2 and num-ss-ports = 1.
>>
>> If the user skips ss-phy-1, then phy-names would be something like the
>> below:
>>
>> phy-names = "usb2-port0", "usb2-port-1",  "usb3-port1";
>>
>> We need to handle two types of interpretations here while parsing the
>> phy-names:
>>
>> a) There are 2 SS Phy's and we just skipped the first one. In this scenario,
>> if we consider (num-ss-ports = 2) and (num-ports = 2) by using the above
>> formula as reference, we configure both GUSB3PIPECTL registers present in
>> the address map although we never use SS Phy-1 but nothing must break. All
>> ports would still work as the user intends with the exception of
>> GUSB3PIPECTL1 (for-port1) still being modified.
>>
>> b) The second interpretation is something like, port-1 is only HS capable
>> and only Port-2 is SS Capable, and so in the phy-names only port-2 has been
>> provided a SS Phy. Just by parsing through the phy-names, it would not be
>> possible to get that info. So if we consider num-ss-ports as 2 in this
>> scenario, we end up meddling with wrong registers (as there is only 1
>> GUSB3PIPECTL reg and we are assuing there are 2). I wanted to make sure that
>> this scenario was not possible.
>>
>> num-ss-ports = max_port_index (usb3-portX) + 1
>> num-ports = max (max_port_index(usb2-portX), max_port_index(usb2-portX)) + 1
>>
>> Taking case of a quad port controller with all ports SS Capable, if the user
>> wants to completely skip port-4. Then with above formula, we get (num-ports
>> = 3) and (num-ss-ports = 3) by parsing the phy-names and we will configure
>> exactly those dwc3-phy registers and not touch the port-4 registers which is
>> still fine.
>>
>> Please let me know if the above idea helps us in this scenario.
>>
> 
> This becomes rather more complicated because the user can skip certain
> port in the DT. We have access to the host registers. Can we just
> temporarily map and access HCSPARAMS1 to get the MAXPORTS and each port
> capability before handing control over to the xHCI driver. We would be
> able to get the num_ports and num_ss_ports then.
> 
> Similarly, the xhci driver doesn't care whether the user skips certain
> port in the DT, it only checks and operates based on the capability
> registers.
> 
> If we have the exact num_ports and num_ss_ports, we can be sure the
> setting to GUSB3PIPECTLn and GUSB2PHYCFGn are valid.
> 
Hi Thinh,

Thanks for the review.
Sure, I can explore this option and get the port info. This must make 
things easier.

Regards,
Krishna,