linux-kernel - Re: [PATCH] PCI: qcom: Enable clocks only after PARF

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Message-ID: <62c8d3e8.1c69fb81.26eee.0249@mx.google.com>
Date:   Sat, 9 Jul 2022 03:03:34 +0200
From:   Christian Marangi <ansuelsmth@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Stanimir Varbanov <svarbanov@...sol.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] PCI: qcom: Enable clocks only after PARF_PHY setup for
 rev 2.1.0

On Fri, Jul 08, 2022 at 06:01:55PM -0500, Bjorn Helgaas wrote:
> On Sat, Jul 09, 2022 at 12:27:43AM +0200, Christian Marangi wrote:
> > We currently enable clocks BEFORE we write to PARF_PHY_CTRL reg to
> > enable clocks and resets. This case the driver to never set to a ready
> > state with the error 'Phy link never came up'.
> > 
> > This in fact is caused by the phy clock getting enabled before setting
> > the required bits in the PARF regs.
> > 
> > A workaround for this was set but with this new discovery we can drop
> > the workaround and use a proper solution to the problem by just enabling
> > the clock only AFTER the PARF_PHY_CTRL bit is set.
> > 
> > This correctly setup the pcie line and makes it usable even when a
> > bootloader leave the pcie line to a underfined state.
> 
> Is "pcie" here a signal name?  Maybe this refers to the "PCIe link"?
>

Hi,
no i was referring to PCIe link. Fell free to fix it if it's not a
problem (or if you want i can just resend)

> > Fixes: 82a823833f4e ("PCI: qcom: Add Qualcomm PCIe controller driver")
> > Cc: stable@...r.kernel.org # v5.4+
> > Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
> 
> Thanks, I put this on
> https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git,
> pci/ctrl/qcom-pending branch (head 47b4ec9d2e60).
> 
> Can you take a look and make sure I didn't mess up the conflict
> resolution with the rest of the series?

Think something went wrong in the rebase as the patch fixup is reverted.

11946f8b6e77a6794c111aafef7772e9967d9a54 is still wrong.

clk_bulk_prepare_enable must be after 
writel(val, pcie->parf + PCIE20_PARF_PHY_CTRL);
so in the post init.

> 
> > ---
> >  drivers/pci/controller/dwc/pcie-qcom.c | 10 ++++------
> >  1 file changed, 4 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > index 2ea13750b492..da13a66ced14 100644
> > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > @@ -337,8 +337,6 @@ static int qcom_pcie_init_2_1_0(struct qcom_pcie *pcie)
> >  	reset_control_assert(res->ext_reset);
> >  	reset_control_assert(res->phy_reset);
> >  
> > -	writel(1, pcie->parf + PCIE20_PARF_PHY_CTRL);
> > -
> >  	ret = regulator_bulk_enable(ARRAY_SIZE(res->supplies), res->supplies);
> >  	if (ret < 0) {
> >  		dev_err(dev, "cannot enable regulators\n");
> > @@ -381,15 +379,15 @@ static int qcom_pcie_init_2_1_0(struct qcom_pcie *pcie)
> >  		goto err_deassert_axi;
> >  	}
> >  
> > -	ret = clk_bulk_prepare_enable(ARRAY_SIZE(res->clks), res->clks);
> > -	if (ret)
> > -		goto err_clks;
> > -
> >  	/* enable PCIe clocks and resets */
> >  	val = readl(pcie->parf + PCIE20_PARF_PHY_CTRL);
> >  	val &= ~BIT(0);
> >  	writel(val, pcie->parf + PCIE20_PARF_PHY_CTRL);
> >  
> > +	ret = clk_bulk_prepare_enable(ARRAY_SIZE(res->clks), res->clks);
> > +	if (ret)
> > +		goto err_clks;
> > +
> >  	if (of_device_is_compatible(node, "qcom,pcie-ipq8064") ||
> >  	    of_device_is_compatible(node, "qcom,pcie-ipq8064-v2")) {
> >  		writel(PCS_DEEMPH_TX_DEEMPH_GEN1(24) |
> > -- 
> > 2.36.1
> > 

-- 
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