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Date:   Mon, 9 May 2022 12:16:31 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>
Cc:     ryder.lee@mediatek.com, jianjun.wang@mediatek.com,
        lorenzo.pieralisi@arm.com, robh@kernel.org, kw@linux.com,
        bhelgaas@google.com, p.zabel@pengutronix.de,
        matthias.bgg@gmail.com, linux-pci@vger.kernel.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, kernel@collabora.com,
        nfraprado@collabora.com
Subject: Re: [PATCH] PCI: mediatek-gen3: Assert resets to ensure expected
 init state
Message-ID: <20220509171631.GA605998@bhelgaas>
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On Mon, May 09, 2022 at 02:18:34PM +0200, AngeloGioacchino Del Regno wrote:
> Il 04/04/22 16:48, AngeloGioacchino Del Regno ha scritto:
> > The controller may have been left out of reset by the bootloader,
> > in which case, before the powerup sequence, the controller will be
> > found preconfigured with values that were set before booting the
> > kernel: this produces a controller failure, with the result of
> > a failure during the mtk_pcie_startup_port() sequence as the PCIe
> > link never gets up.
> > 
> > To ensure that we get a clean start in an expected state, assert
> > both the PHY and MAC resets before executing the controller
> > power-up sequence.
> > 
> > Fixes: d3bf75b579b9 ("PCI: mediatek-gen3: Add MediaTek Gen3 driver for MT8192")
> > Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> 
> Friendly ping for an important fix :-)

d3bf75b579b9 appeared in v5.13-rc1 (May 2021, a year ago), so I assume
this is important for v5.19, but not urgent enough to require being in
v5.18.  Right?

> > ---
> >   drivers/pci/controller/pcie-mediatek-gen3.c | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
> > index f7048ea4c020..dccdfce12b1c 100644
> > --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> > +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> > @@ -838,6 +838,14 @@ static int mtk_pcie_setup(struct mtk_gen3_pcie *pcie)
> >   	if (err)
> >   		return err;
> > +	/*
> > +	 * The controller may have been left out of reset by the bootloader
> > +	 * so make sure that we get a clean start by asserting resets here.
> > +	 */
> > +	reset_control_assert(pcie->phy_reset);
> > +	reset_control_assert(pcie->mac_reset);
> > +	usleep_range(10, 20);
> > +
> >   	/* Don't touch the hardware registers before power up */
> >   	err = mtk_pcie_power_up(pcie);
> >   	if (err)
> 
> 
> 
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