linux-kernel - Re: [PATCH] PCI: mediatek-gen3: Assert resets to ensure expected init state

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Message-ID: <e9839acf-e334-d73d-a0b3-57d951fb8796@collabora.com>
Date:   Mon, 9 May 2022 14:18:34 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     ryder.lee@...iatek.com
Cc:     jianjun.wang@...iatek.com, lorenzo.pieralisi@....com,
        robh@...nel.org, kw@...ux.com, bhelgaas@...gle.com,
        p.zabel@...gutronix.de, matthias.bgg@...il.com,
        linux-pci@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kernel@...labora.com, nfraprado@...labora.com
Subject: Re: [PATCH] PCI: mediatek-gen3: Assert resets to ensure expected init
 state

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@...labora.com>

Friendly ping for an important fix :-)

Regards,
Angelo

> ---
>   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)