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

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Message-ID: <20191021140424.GR47056@e119886-lin.cambridge.arm.com>
Date:   Mon, 21 Oct 2019 15:04:25 +0100
From:   Andrew Murray <andrew.murray@....com>
To:     Anvesh Salveru <anvesh.s@...sung.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        bhelgaas@...gle.com, gustavo.pimentel@...opsys.com,
        jingoohan1@...il.com, lorenzo.pieralisi@....com,
        Pankaj Dubey <pankaj.dubey@...sung.com>
Subject: Re: [PATCH 2/2] PCI: dwc: Add support to handle ZRX-DC Compliant PHYs

On Mon, Oct 21, 2019 at 05:59:53PM +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

s/is to/to the/

> it helps in low power consumption during power states.

s/in low/lower/

> 
> 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 "snps,phy-zrxdc-compliant"
> property in controller DT node 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>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
>  drivers/pci/controller/dwc/pcie-designware.h | 3 +++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 820488dfeaed..6560d9f765d7 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -556,4 +556,11 @@ 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 (of_property_read_bool(np, "snps,phy-zrxdc-compliant")) {
> +		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);
> +	}
> +

Given that this duplicates tegra_pcie_prepare_host in pcie-tegra194.c, can
we update that driver to adopt this new binding?

Thanks,

Andrew Murray

>  }
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 5a18e94e52c8..427a55ec43c6 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
> -- 
> 2.17.1
>