linux-kernel - Re: [PATCH v1] clk: qcom: gcc-sc8280xp: add cxo as parent for gcc_ufs_ref_clkref

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Date:   Fri, 4 Nov 2022 10:29:30 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Bjorn Andersson <andersson@...nel.org>
Cc:     Shazad Hussain <quic_shazhuss@...cinc.com>,
        Stephen Boyd <sboyd@...nel.org>, bmasney@...hat.com,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] clk: qcom: gcc-sc8280xp: add cxo as parent for
 gcc_ufs_ref_clkref_clk

On Thu, Nov 03, 2022 at 10:23:55AM -0500, Bjorn Andersson wrote:
> On Thu, Nov 03, 2022 at 10:06:20AM +0100, Johan Hovold wrote:
> > On Wed, Nov 02, 2022 at 09:49:49PM -0500, Bjorn Andersson wrote:

> > > In line with the downstream dts, we have GCC_UFS{,_1}_CARD_CLKREF_CLK
> > > providing a reference clock to the two phys. Then GCC_UFS_REF_CLKREF_CLK
> > > feeds the UFS refclock pads (both of them), which connect to the memory
> > > device(s).
> > > 
> > > In other words, GCC_UFS{,_1}_CARD_CLKREF_CLK should be "ref" in
> > > respective phy.
> > > 
> > > GCC_UFS_REF_CLKREF_CLK is the clock to the devices, but as we don't
> > > represent the memory device explicitly it seems suitable to use as
> > > "ref_clk" in the ufshc nodes - which would then match the special
> > > handling of the "link clock" in the UFS driver.
> > 
> > Thanks for clearing that up. Using GCC_UFS_REF_CLKREF_CLK as ref_clk for
> > the controller sounds reasonable.
> > 
> > I guess the only missing piece is which "card" ref clock is used by
> > which PHY.
> > 
> > The ADP dts uses:
> > 
> > 	phy			ref clock
> > 
> > 	phy@...7000 (UFS_PHY)	GCC_UFS_CARD_CLKREF_CLK
> > 	phy@...7000 (UFS_CARD)	GCC_UFS_1_CARD_CLKREF_CLK
> > 
> 
> This matches the documentation.

Thanks for checking.

> > > All three clocks are sourced off the CXO pad, so I would like this patch
> > > to cover at least all of these. And
> > > 
> > > Fixes: d65d005f9a6c ("clk: qcom: add sc8280xp GCC driver")
> > > 
> > > seems to be in order for such patch.
> > > 
> > > 
> > > @Johan, would you mind writing a dts patch flipping the clocks around
> > > and Shazad can update this patch?
> > 
> > I'll do so, but I'll wait with posting until you can confirm which
> > clkref is which.

I've know posted a patch fixing the devicetree here:

	https://lore.kernel.org/lkml/20221104092045.17410-1-johan+linaro@kernel.org/

Note that we need to get Shazad's clock driver fix in first as the UFS
controller driver expects a valid frequency for the device ref clock.

Johan