linux-kernel - RE: [PATCH v1] soc: imx: imx8mp-blk-ctrl: Add PCIe SYSPLL configurations

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Message-ID: <AS8PR04MB8676B7207B48F94BF12C88EE8C399@AS8PR04MB8676.eurprd04.prod.outlook.com>
Date:   Wed, 2 Nov 2022 01:45:36 +0000
From:   Hongxing Zhu <hongxing.zhu@....com>
To:     Lucas Stach <l.stach@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>
CC:     "marex@...x.de" <marex@...x.de>,
        "tharvey@...eworks.com" <tharvey@...eworks.com>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "alexander.stein@...tq-group.com" <alexander.stein@...tq-group.com>,
        "richard.leitner@...ux.dev" <richard.leitner@...ux.dev>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>
Subject: RE: [PATCH v1] soc: imx: imx8mp-blk-ctrl: Add PCIe SYSPLL
 configurations

> -----Original Message-----
> From: Lucas Stach <l.stach@...gutronix.de>
> Sent: 2022年11月1日 16:45
> To: Shawn Guo <shawnguo@...nel.org>; Hongxing Zhu
> <hongxing.zhu@....com>
> Cc: marex@...x.de; tharvey@...eworks.com; vkoul@...nel.org;
> bhelgaas@...gle.com; lorenzo.pieralisi@....com;
> alexander.stein@...tq-group.com; richard.leitner@...ux.dev;
> devicetree@...r.kernel.org; linux-pci@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> kernel@...gutronix.de; dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH v1] soc: imx: imx8mp-blk-ctrl: Add PCIe SYSPLL
> configurations
> 
> Hi Shawn, Richard,
> 
> Am Samstag, dem 29.10.2022 um 16:45 +0800 schrieb Shawn Guo:
> > On Mon, Oct 24, 2022 at 01:43:09PM +0800, Richard Zhu wrote:
> > > Add PCIe SYSPLL configurations, thus the internal SYSPLL can be used
> > > as i.MX8MP PCIe reference clock.
> > >
> > > The following properties of PHY dts node should be changed accordingly.
> > >   - Set 'fsl,refclk-pad-mode' as '<IMX8_PCIE_REFCLK_PAD_OUTPUT>'.
> > >   - Change 'clocks' to '<&clk IMX8MP_CLK_HSIO_ROOT>'.
> > >
> > > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> >
> > Applied, thanks!
> 
> Sorry for the late reply, but I'm not really happy with the fact that the PLL is
> now unconditionally enabled, even though it is only needed when there is no
> external reference clock source.
> I fear that this will be hard to correct later on as the DT abstraction is wrong, as
> IMX8MP_CLK_HSIO_ROOT is NOT the reference clock for the PHY, but the PLL
> generated clock, which isn't properly exposed with this series.
Hi Lucas:
First of all, thanks for your comments.

IMHO, I'm not sure it's proper or not to describe the hardware logic in
 the PHY node when internal SYSPLL is used as PCIe PHY reference clock.
So, I'm trying to get some suggestions and used to send out an email to
 you and Marcel on Sep20.

Okay, if you think it's not correct to expose IMX8MP_CLK_HSIO_ROOT clock
 out.
Which clock you are prefer to use as PHY reference clock here?

Thanks.

Best Regards
Richard Zhu
> 
> I'm not happy to see this going in in the current state and if not too late would
> like to ask Shawn to remove it from the tree again.
> 
> Regards,
> Lucas