linux-kernel - Re: [PATCH v6 2/2] PCI: dwc: add support to handle ZRX-DC Compliant PHYs

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Message-ID: <20191216104820.GQ24359@e119886-lin.cambridge.arm.com>
Date:   Mon, 16 Dec 2019 10:48:20 +0000
From:   Andrew Murray <andrew.murray@....com>
To:     Anvesh Salveru <anvesh.s@...sung.com>
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        kishon@...com, jingoohan1@...il.com, gustavo.pimentel@...opsys.com,
        lorenzo.pieralisi@....com, bhelgaas@...gle.com,
        pankaj.dubey@...sung.com, mark.rutland@....com, robh+dt@...nel.org
Subject: Re: [PATCH v6 2/2] PCI: dwc: add support to handle ZRX-DC Compliant
 PHYs

On Fri, Dec 13, 2019 at 06:43:20PM +0530, Anvesh Salveru wrote:
> Many platforms use DesignWare controller but the PHY can be different in
> different platforms. If the PHY is compliant is to ZRX-DC specification
> it helps in low power consumption during power states.
> 
> If current data rate is 8.0 GT/s or higher and PHY is not compliant to
> ZRX-DC specification, then after every 100ms link should transition to
> recovery state during the low power states.
> 
> DesignWare controller provides GEN3_ZRXDC_NONCOMPL field in
> GEN3_RELATED_OFF to specify about ZRX-DC compliant PHY.
> 
> Platforms with ZRX-DC compliant PHY can set phy_zrxdc_compliant variable
> to specify this property to the controller.
> 
> Signed-off-by: Anvesh Salveru <anvesh.s@...sung.com>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
> ---
> Changes w.r.t v5:
>  - None
> 
>  drivers/pci/controller/dwc/pcie-designware.c | 6 ++++++
>  drivers/pci/controller/dwc/pcie-designware.h | 4 ++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 820488d..36a01b7 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -556,4 +556,10 @@ void dw_pcie_setup(struct dw_pcie *pci)
>  		       PCIE_PL_CHK_REG_CHK_REG_START;
>  		dw_pcie_writel_dbi(pci, PCIE_PL_CHK_REG_CONTROL_STATUS, val);
>  	}
> +
> +	if (pci->phy_zrxdc_compliant) {

This series doesn't update any DWC drivers to actually test and set the
phy_zrxdc_compliant flag. There isn't good justification for merging this
unless it has a user.

Thanks,

Andrew Murray

> +		val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> +		val &= ~PORT_LOGIC_GEN3_ZRXDC_NONCOMPL;
> +		dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> +	}
>  }
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 5accdd6..36f7579 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -60,6 +60,9 @@
>  #define PCIE_MSI_INTR0_MASK		0x82C
>  #define PCIE_MSI_INTR0_STATUS		0x830
>  
> +#define PCIE_PORT_GEN3_RELATED		0x890
> +#define PORT_LOGIC_GEN3_ZRXDC_NONCOMPL	BIT(0)
> +
>  #define PCIE_ATU_VIEWPORT		0x900
>  #define PCIE_ATU_REGION_INBOUND		BIT(31)
>  #define PCIE_ATU_REGION_OUTBOUND	0
> @@ -249,6 +252,7 @@ struct dw_pcie {
>  	void __iomem		*atu_base;
>  	u32			num_viewport;
>  	u8			iatu_unroll_enabled;
> +	bool			phy_zrxdc_compliant;
>  	struct pcie_port	pp;
>  	struct dw_pcie_ep	ep;
>  	const struct dw_pcie_ops *ops;
> -- 
> 2.7.4
>