linux-kernel - Re: [PATCH v3] PCI: imx6: Add PHY reference clock source support

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Message-ID: <20180307115438.GA15139@e107981-ln.cambridge.arm.com>
Date:   Wed, 7 Mar 2018 11:54:38 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Ilya Ledvich <ilya@...pulab.co.il>
Cc:     Lucas Stach <l.stach@...gutronix.de>,
        Richard Zhu <hongxing.zhu@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v3] PCI: imx6: Add PHY reference clock source support

On Wed, Jan 10, 2018 at 03:43:41PM +0200, Ilya Ledvich wrote:
> Hi Lucas,
> 
> On 01/08/2018 12:43 PM, Lucas Stach wrote:
> >Am Donnerstag, den 04.01.2018, 15:52 +0200 schrieb Ilya Ledvich:
> >>i.MX7D variant of the IP can use either Crystal Oscillator input
> >>or internal clock input as a Reference Clock input for PCIe PHY.
> >>Add support for an optional property 'fsl,pcie-phy-refclk-internal'.
> >>If present then an internal clock input is used as PCIe PHY
> >>reference clock source. By default an external oscillator input
> >>is still used.
> >>
> >>Verified on Compulab SBC-iMX7 Single Board Computer.
> >
> >Sorry to get in late here, but I would rather have the external clock
> >input modeled as a real clock and only use the internal clock if that
> >isn't present.
> >
> 
> I tried to follow the logic described in the iMX7 TRM, where external
> oscillator is a default option. Additionally, the external clock input model
> you've suggested, requires additional changes in the iMX7 SabreSD board (and
> probably other boards which use an external input too) devicetree files.
> 
> >Are you even sure that the i.MX7 clock you mention isn't the already
> >documented "pcie_bus" clock? This one is also allowed to be sourced
> >externally on the i.MX6.
> 
> To the best of my understanding it's not the pcie_bus clock, but I'm
> absolutely sure. Could anybody from the BSP team guys elaborate on this
> issue? Thanks a lot!

I have marked this with "Changes Requested" according to Lucas'
feedback, please send a new version or let me know what I should
do with it, thanks.

Lorenzo