linux-kernel - Re: [PATCH v2] PCI: qcom: fix IPQ8074 Gen2 support

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Message-ID: <6f22fe3a-2197-b373-8c48-5c146648166e@linaro.org>
Date:   Wed, 22 Jun 2022 10:03:42 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Robert Marko <robimarko@...il.com>, svarbanov@...sol.com,
        agross@...nel.org, bjorn.andersson@...aro.org,
        lpieralisi@...nel.org, robh@...nel.org, kw@...ux.com,
        bhelgaas@...gle.com, p.zabel@...gutronix.de, jingoohan1@...il.com,
        linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, johan+linaro@...nel.org
Subject: Re: [PATCH v2] PCI: qcom: fix IPQ8074 Gen2 support

On 22/06/2022 00:16, Bjorn Helgaas wrote:
> On Tue, Jun 21, 2022 at 11:45:12PM +0300, Dmitry Baryshkov wrote:
>> On Tue, 21 Jun 2022 at 23:32, Bjorn Helgaas <helgaas@...nel.org> wrote:
>>> On Tue, Jun 21, 2022 at 01:23:30PM +0200, Robert Marko wrote:
>>>> IPQ8074 has one Gen2 and one Gen3 port, currently the Gen2 port will
>>>> cause the system to hang as its using DBI registers in the .init
>>>> and those are only accesible after phy_power_on().
>>>
>>> Is the fact that IPQ8074 has both a Gen2 and a Gen3 port relevant to
>>> this patch?  I don't see the connection.
>>>
>>> I see that qcom_pcie_host_init() does:
>>>
>>>    qcom_pcie_host_init
>>>      pcie->cfg->ops->init(pcie)
>>>      phy_power_on(pcie->phy)
>>>      pcie->cfg->ops->post_init(pcie)
>>>
>>> and that you're moving DBI register accesses from
>>> qcom_pcie_init_2_3_3() to qcom_pcie_post_init_2_3_3().
>>>
>>> But I also see DBI register accesses in other .init() functions:
>>>
>>>    qcom_pcie_init_2_1_0
>>>    qcom_pcie_init_1_0_0      (oddly out of order)
>>>    qcom_pcie_init_2_3_2
>>>    qcom_pcie_init_2_4_0
>>>
>>> Why do these accesses not need to be moved?  I assume it's because
>>> pcie->phy is an optional PHY and phy_power_on() does nothing on those
>>> controllers?
>>>
>>> Whatever the reason, I think the DBI accesses should be done
>>> consistently in .post_init().  I see that Dmitry's previous patches
>>> removed all those .post_init() functions, but I think the consistency
>>> is worth having.
>>>
>>> Perhaps we could reorder the patches so this patch comes first, moves
>>> the DBI accesses into .post_init(), then Dmitry's patches could be
>>> rebased on top to drop the clock handling?
>>
>> I don't think there is a need to reorder patches. My patches do not
>> remove support for post_init(), they drop the callbacks code. Thus one
>> can reinstate necessary code back.
> 
> There's not a *need* to reorder them, but I think it would make the
> patches smaller and more readable because we wouldn't be removing and
> then re-adding the functions.

Ack. I'm fine then with rebasing my patches on top of Robert's patchset. 
I'll send the next revision after getting this patchset into the form.

-- 
With best wishes
Dmitry