linux-kernel - Re: [PATCH v5 0/9] PCI: Enable Power and configure the TC9563 PCIe switch

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Message-ID: <91549089-f66b-8e2c-9708-d880f3bf1a0c@oss.qualcomm.com>
Date: Sat, 19 Apr 2025 08:56:08 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        chaitanya chundru <quic_krichai@...cinc.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        cros-qcom-dts-watchers@...omium.org, Jingoo Han <jingoohan1@...il.com>,
        Bartosz Golaszewski <brgl@...ev.pl>, quic_vbadigan@...cnic.com,
        amitk@...nel.org, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, jorge.ramirez@....qualcomm.com,
        Dmitry Baryshkov <lumag@...nel.org>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v5 0/9] PCI: Enable Power and configure the TC9563 PCIe
 switch



On 4/19/2025 1:30 AM, Bjorn Helgaas wrote:
> On Sat, Apr 12, 2025 at 07:19:49AM +0530, Krishna Chaitanya Chundru wrote:
>> TC9563 is the PCIe switch which has one upstream and three downstream
>> ports. To one of the downstream ports ethernet MAC is connected as endpoint
>> device. Other two downstream ports are supposed to connect to external
>> device. One Host can connect to TC956x by upstream port.
> 
> I guess this topology is for one specific platform that includes the
> TC9563?  Since it's a PCIe switch, I assume it could also be used in
> other platforms with other topologies?
> 
This topology is for the switch not for per platform, the switch exposes
two DSP's for external device and one DSP has always integrated MAC.
>> TC9563 switch power is controlled by the GPIO's. After powering on
>> the switch will immediately participate in the link training. if the
>> host is also ready by that time PCIe link will established.
>>
>> The TC9563 needs to configured certain parameters like de-emphasis,
>> disable unused port etc before link is established.
>>
>> As the controller starts link training before the probe of pwrctl driver,
>> the PCIe link may come up as soon as we power on the switch. Due to this
>> configuring the switch itself through i2c will not have any effect as
>> this configuration needs to done before link training. To avoid this
>> introduce two functions in pci_ops to start_link() & stop_link() which
>> will disable the link training if the PCIe link is not up yet.
>>
>> This series depends on the https://lore.kernel.org/all/20250124101038.3871768-3-krishna.chundru@oss.qualcomm.com/
> 
> How so?
> https://lore.kernel.org/all/20250124101038.3871768-3-krishna.chundru@oss.qualcomm.com/
> adds a schema "n-fts" property, but this series doesn't mention
> "n-fts".  This series *does* add this:
> 
>    of_property_read_u8_array(node, "nfts", cfg->nfts, 2);
> 
> Is that supposed to be the same thing, or does "nfts" magically match
> "n-fts"?
>
It is miss from my side, thanks for pointing out, I will
fix this in next patch series.

- Krishna Chaitanya.

> Bjorn