From: Krishna Kurapati PSSNV <quic_kriskura@quicinc.com>
To: Johan Hovold <johan@kernel.org>
Cc: Bjorn Andersson <andersson@kernel.org>,
Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Philipp Zabel <p.zabel@pengutronix.de>,
Andy Gross <agross@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-kernel@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
<devicetree@vger.kernel.org>, <quic_pkondeti@quicinc.com>,
<quic_ppratap@quicinc.com>, <quic_wcheng@quicinc.com>,
<quic_jackp@quicinc.com>, <quic_harshq@quicinc.com>,
<ahalaney@redhat.com>
Subject: Re: [PATCH v8 6/9] usb: dwc3: qcom: Add multiport controller support for qcom wrapper
Date: Thu, 8 Jun 2023 01:21:02 +0530 [thread overview]
Message-ID: <99cded6f-6a71-ffce-8479-c7c0726bfb8e@quicinc.com> (raw)
In-Reply-To: <ZIBsDQJtgDZRe7MG@hovoldconsulting.com>
On 6/7/2023 5:07 PM, Johan Hovold wrote:
> Hi Krishna,
>
> and sorry about the delay in following up on this. As usual, there are
> just way too many threads and this one in particular requires a bit of
> thought.
>
Hi Johan,
Thanks for taking the time out and reviewing the patches again.
> On Sat, May 20, 2023 at 11:18:52PM +0530, Krishna Kurapati PSSNV wrote:
>> On 5/17/2023 10:07 PM, Johan Hovold wrote:
>
>>> I don't think we should be adding more of these layering violations. A
>>> parent device driver has no business messing with the driver data for a
>>> child device which may or may not even have probed yet.
>>>
>>> I added a FIXME elsewhere in the driver about fixing up the current
>>> instances that have already snuck in (which in some sense is even worse
>>> by accessing driver data of a grandchild device).
>>>
>>> We really need to try sort this mess out and how to properly handle the
>>> interactions between these layers (e.g. glue, dwc3 core and xhci). This
>>> will likely involve adding callbacks from the child to the parent, for
>>> example, when the child is suspending.
>
>> I agree with you, but in this case I believe there is no other way we
>> can find the number of ports present. Unless its a dt property which
>> parent driver can access the child's of node and get the details. Like
>> done in v4 [1]. But it would be adding redundant data into DT as pointed
>> out by Rob and Krzysztof and so we removed these properties.
>
> So there at least two issues with this series:
>
> 1. accessing xhci registers from the dwc3 core
> 2. accessing driver data of a child device
>
> 1. The first part about accessing xhci registers goes against the clear
> separation between glue, core and xhci that Felipe tried to maintain.
>
> I'm not entirely against doing this from the core driver before
> registering the xhci platform device as the registers are unmapped
> afterwards. But if this is to be allowed, then the implementation should
> be shared with xhci rather than copied verbatim.
>
> The alternative that avoids this issue entirely could indeed be to
> simply count the number of PHYs described in DT as Rob initially
> suggested. Why would that not work?
>
The reason why I didn't want to read the Phy's from DT is explained in
[1]. I felt it makes the code unreadable and its very tricky to read the
phy's properly, so we decided we would initialize phy's for all ports
and if a phy is missing in DT, the corresponding member in
dwc->usbX_generic_phy[] would be NULL and any phy op on it would be a NOP.
Also as per Krzysztof suggestion on [2], we can add a compatible to read
number of phy's / ports present. This avoids accessing xhci members
atleast in driver core. But the layering violations would still be present.
> 2. The driver is already accessing driver data of the child device so
> arguably your series is not really making things much worse than they
> already are.
>
> I've just sent a couple of fixes to address some of the symptoms of
> this layering violation here:
>
> https://lore.kernel.org/lkml/20230607100540.31045-1-johan+linaro@kernel.org/
>
As you pointed out offline to me that using xhci event notifiers I
mentioned on [3], if it is not acceptable to use them as notifications
to check whether we are in host mode, I believe the only way would be to
use the patches you pushed in.
> Getting this fixed properly is going to take a bit of work, and
> depending on how your multiport wake up implementation is going to look
> like, adding support for multiport controllers may not make this much
> harder to address.
>
> So perhaps we can indeed merge support for multiport and then get back
> to cleaning this up.
So, you are referring to use the patches you pushed today as a partial
way to cleanup layering violations and merge multiport on top of it ? If
so, I am fine with it. I can rebase my changes on top of them.
[1]:
https://lore.kernel.org/all/4eb26a54-148b-942f-01c6-64e66541de8b@quicinc.com/
[2]:
https://lore.kernel.org/all/ca729f62-672e-d3de-4069-e2205c97e7d8@linaro.org/
[3]:
https://lore.kernel.org/all/37fd026e-ecb1-3584-19f3-f8c1e5a9d20a@quicinc.com/
Regards,
Krishna,
next prev parent reply other threads:[~2023-06-07 19:51 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-14 5:49 [PATCH v8 0/9] Add multiport support for DWC3 controllers Krishna Kurapati
2023-05-14 5:49 ` [PATCH v8 1/9] dt-bindings: usb: qcom,dwc3: Add bindings for SC8280 Multiport Krishna Kurapati
2023-05-14 9:46 ` Krzysztof Kozlowski
2023-05-16 10:59 ` Johan Hovold
2023-05-17 11:10 ` Krishna Kurapati PSSNV
2023-05-17 11:44 ` Johan Hovold
2023-05-17 12:19 ` Krishna Kurapati PSSNV
2023-05-17 12:55 ` Johan Hovold
2023-05-14 5:49 ` [PATCH v8 2/9] dt-bindings: usb: Add bindings for multiport properties on DWC3 controller Krishna Kurapati
2023-05-14 5:49 ` [PATCH v8 3/9] usb: dwc3: core: Access XHCI address space temporarily to read port info Krishna Kurapati
2023-05-15 21:08 ` Bjorn Andersson
2023-05-16 2:12 ` Krishna Kurapati PSSNV
2023-05-16 22:39 ` Thinh Nguyen
2023-05-16 12:11 ` Johan Hovold
2023-05-16 15:02 ` Krishna Kurapati PSSNV
2023-05-17 3:10 ` Krishna Kurapati PSSNV
2023-05-17 3:21 ` Thinh Nguyen
2023-05-17 7:46 ` Johan Hovold
2023-05-17 23:21 ` Thinh Nguyen
2023-06-07 11:56 ` Johan Hovold
2023-05-17 7:35 ` Johan Hovold
2023-05-17 12:21 ` Krishna Kurapati PSSNV
2023-05-17 15:10 ` Johan Hovold
2023-05-14 5:49 ` [PATCH v8 4/9] usb: dwc3: core: Skip setting event buffers for host only controllers Krishna Kurapati
2023-05-15 21:19 ` Bjorn Andersson
2023-05-16 12:17 ` Johan Hovold
2023-05-16 14:28 ` Krishna Kurapati PSSNV
2023-05-14 5:49 ` [PATCH v8 5/9] usb: dwc3: core: Refactor PHY logic to support Multiport Controller Krishna Kurapati
2023-05-15 21:47 ` Bjorn Andersson
2023-05-16 2:31 ` Krishna Kurapati PSSNV
2023-05-17 16:17 ` Johan Hovold
2023-05-14 5:49 ` [PATCH v8 6/9] usb: dwc3: qcom: Add multiport controller support for qcom wrapper Krishna Kurapati
2023-05-15 22:27 ` Bjorn Andersson
2023-05-16 2:19 ` Krishna Kurapati PSSNV
2023-05-17 16:37 ` Johan Hovold
2023-05-20 17:48 ` Krishna Kurapati PSSNV
2023-06-07 11:37 ` Johan Hovold
2023-06-07 19:51 ` Krishna Kurapati PSSNV [this message]
2023-06-08 9:42 ` Johan Hovold
2023-06-08 15:23 ` Krishna Kurapati PSSNV
2023-06-08 17:57 ` Thinh Nguyen
2023-06-09 8:18 ` Johan Hovold
2023-06-09 18:16 ` Thinh Nguyen
2023-06-15 4:20 ` Krishna Kurapati PSSNV
2023-06-15 21:08 ` Thinh Nguyen
2023-06-21 7:38 ` Johan Hovold
2023-06-22 4:39 ` Krishna Kurapati PSSNV
2023-06-21 7:34 ` Johan Hovold
2023-06-22 22:41 ` Thinh Nguyen
2023-05-26 2:55 ` Bjorn Andersson
2023-05-26 15:25 ` Krishna Kurapati PSSNV
2023-06-07 11:44 ` Johan Hovold
2023-06-07 19:55 ` Krishna Kurapati PSSNV
2023-06-08 9:44 ` Johan Hovold
2023-06-07 12:16 ` Johan Hovold
2023-06-27 15:43 ` Johan Hovold
2023-07-02 19:05 ` Krishna Kurapati PSSNV
2023-07-14 9:00 ` Johan Hovold
2023-07-14 10:38 ` Krishna Kurapati PSSNV
2023-07-21 11:16 ` Johan Hovold
2023-07-21 12:10 ` Konrad Dybcio
2023-07-21 12:54 ` Johan Hovold
2023-08-11 16:48 ` Konrad Dybcio
2023-08-12 8:58 ` Krishna Kurapati PSSNV
2023-05-14 5:49 ` [PATCH v8 7/9] arm64: dts: qcom: sc8280xp: Add multiport controller node for SC8280 Krishna Kurapati
2023-05-15 14:26 ` Johan Hovold
2023-05-15 15:32 ` Krishna Kurapati PSSNV
2023-05-16 10:54 ` Johan Hovold
2023-05-16 14:24 ` Krishna Kurapati PSSNV
2023-05-16 14:42 ` Johan Hovold
2023-05-16 14:44 ` Krishna Kurapati PSSNV
2023-05-14 5:49 ` [PATCH v8 8/9] arm64: dts: qcom: sa8295p: Enable tertiary controller and its 4 USB ports Krishna Kurapati
2023-05-14 5:49 ` [PATCH v8 9/9] arm64: dts: qcom: sa8540-ride: Enable first port of tertiary usb controller Krishna Kurapati
2023-05-15 2:40 ` [PATCH v8 0/9] Add multiport support for DWC3 controllers Bjorn Andersson
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