linux-kernel - Re: [PATCH v3] PCI: mediatek-gen3: Disable DVFSRC voltage request

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Message-ID: <c3630f7f-fb3d-6018-c12a-535e891d535a@gmail.com>
Date:   Wed, 17 Nov 2021 18:41:46 +0100
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Jianjun Wang <jianjun.wang@...iatek.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Ryder Lee <ryder.lee@...iatek.com>
Cc:     linux-pci@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        qizhong.cheng@...iatek.com, Ryan-JH.Yu@...iatek.com,
        Tzung-Bi Shih <tzungbi@...gle.com>
Subject: Re: [PATCH v3] PCI: mediatek-gen3: Disable DVFSRC voltage request



On 15/10/2021 08:36, Jianjun Wang wrote:
> When the DVFSRC (dynamic voltage and frequency scaling resource collector)
> feature is not implemented, the PCIe hardware will assert a voltage request
> signal when exit from the L1 PM Substates to request a specific Vcore
> voltage, but cannot receive the voltage ready signal, which will cause
> the link to fail to exit the L1 PM Substates.
> 
> Disable DVFSRC voltage request by default, we need to find a common way to
> enable it in the future.
> 
> Fixes: d3bf75b579b9 ("PCI: mediatek-gen3: Add MediaTek Gen3 driver for MT8192")
> Signed-off-by: Jianjun Wang <jianjun.wang@...iatek.com>
> Reviewed-by: Tzung-Bi Shih <tzungbi@...gle.com>
> Tested-by: Qizhong Cheng <qizhong.cheng@...iatek.com>

Reviewed-by: Matthias Brugger <matthias.bgg@...il.com>

> ---
>   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 f3aeb8d4eaca..79fb12fca6a9 100644
> --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> @@ -79,6 +79,9 @@
>   #define PCIE_ICMD_PM_REG		0x198
>   #define PCIE_TURN_OFF_LINK		BIT(4)
>   
> +#define PCIE_MISC_CTRL_REG		0x348
> +#define PCIE_DISABLE_DVFSRC_VLT_REQ	BIT(1)
> +
>   #define PCIE_TRANS_TABLE_BASE_REG	0x800
>   #define PCIE_ATR_SRC_ADDR_MSB_OFFSET	0x4
>   #define PCIE_ATR_TRSL_ADDR_LSB_OFFSET	0x8
> @@ -297,6 +300,11 @@ static int mtk_pcie_startup_port(struct mtk_pcie_port *port)
>   	val &= ~PCIE_INTX_ENABLE;
>   	writel_relaxed(val, port->base + PCIE_INT_ENABLE_REG);
>   
> +	/* Disable DVFSRC voltage request */
> +	val = readl_relaxed(port->base + PCIE_MISC_CTRL_REG);
> +	val |= PCIE_DISABLE_DVFSRC_VLT_REQ;
> +	writel_relaxed(val, port->base + PCIE_MISC_CTRL_REG);
> +
>   	/* Assert all reset signals */
>   	val = readl_relaxed(port->base + PCIE_RST_CTRL_REG);
>   	val |= PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB;
>