linux-kernel - Re: [PATCH v3 11/28] dt-bindings: usb: dwc3: Add snps,num-hc-interrupters definition

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Message-ID: <9d31db9c-4e58-767a-15c5-65f7c04bd989@quicinc.com>
Date:   Tue, 29 Aug 2023 00:19:09 -0700
From:   Wesley Cheng <quic_wcheng@...cinc.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Rob Herring <robh@...nel.org>
CC:     <srinivas.kandagatla@...aro.org>, <mathias.nyman@...el.com>,
        <perex@...ex.cz>, <broonie@...nel.org>, <lgirdwood@...il.com>,
        <krzysztof.kozlowski+dt@...aro.org>, <agross@...nel.org>,
        <Thinh.Nguyen@...opsys.com>, <bgoswami@...cinc.com>,
        <andersson@...nel.org>, <gregkh@...uxfoundation.org>,
        <tiwai@...e.com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <alsa-devel@...a-project.org>,
        <devicetree@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <quic_jackp@...cinc.com>, <quic_plai@...cinc.com>
Subject: Re: [PATCH v3 11/28] dt-bindings: usb: dwc3: Add
 snps,num-hc-interrupters definition

Hi Krzysztof,

On 8/28/2023 11:33 PM, Krzysztof Kozlowski wrote:
> On 29/08/2023 04:05, Wesley Cheng wrote:
>> Hi Rob,
>>
>> On 3/11/2023 5:40 AM, Rob Herring wrote:
>>> On Wed, Mar 08, 2023 at 03:57:34PM -0800, Wesley Cheng wrote:
>>>> Add a new definition for specifying how many XHCI secondary interrupters
>>>> can be allocated.  XHCI in general can potentially support up to 1024
>>>> interrupters, which some uses may want to limit depending on how many
>>>> users utilize the interrupters.
>>>>
>>>> Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
>>>> ---
>>>>    .../devicetree/bindings/usb/snps,dwc3.yaml          | 13 +++++++++++++
>>>>    1 file changed, 13 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
>>>> index be36956af53b..4e2417191f93 100644
>>>> --- a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
>>>> +++ b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
>>>> @@ -359,6 +359,19 @@ properties:
>>>>        items:
>>>>          enum: [1, 4, 8, 16, 32, 64, 128, 256]
>>>>    
>>>> +  snps,num-hc-interrupters:
>>>> +    description:
>>>> +      Defines the maximum number of XHCI host controller interrupters that can
>>>> +      be supported.  The XHCI host controller has support to allocate multiple
>>>> +      event rings, which can be assigned to different clients/users.  The DWC3
>>>> +      controller has a maximum of 8 interrupters.  If this is not defined then
>>>> +      the value will be defaulted to 1.  This parameter is used only when
>>>> +      operating in host mode.
>>>
>>> Is this an XHCI or DWC3 feature? The former should be added to the XHCI
>>> binding.
>>>
>>
>> Sorry for the late response...message got routed to a folder I don't
>> frequently check...
> 
> That is quite unfortunate, to put our feedback somewhere deep and then
> send new versions of patches thinking there is apparently no feedback.
> Fix your email process, so our reviews are not ignored. If they are, we
> obviously should ignore your patches.
> 

Spent some time fixing filters around, so should be addressed now.

>>
>> This is a XHCI feature, but the DWC3 design is built in a way that DWC3
>> host initializes the XHCI device and populates the properties associated
>> to XHCI dev.
> 
> You speak about driver now, not bindings. If driver has limitations,
> change it. Not really problem of bindings.
> 

Its the limitation of the HW.  Depending on how the SNPS DWC3 controller 
was implemented the vendor it can support less than the value mentioned 
in the Synopsys databook.

Thanks
Wesley Cheng