linux-kernel - RE: [PATCH v2] PCI: dwc: Add support to add GEN3 related equalization quirks

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Message-ID: <DM6PR12MB4010C442FC8B52E2E7A18188DA8C0@DM6PR12MB4010.namprd12.prod.outlook.com>
Date:   Mon, 16 Sep 2019 09:16:19 +0000
From:   Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>
To:     Pankaj Dubey <pankaj.dubey@...sung.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "gustavo.pimentel@...opsys.com" <Gustavo.Pimentel@...opsys.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "andrew.murray@....com" <andrew.murray@....com>,
        Anvesh Salveru <anvesh.s@...sung.com>
Subject: RE: [PATCH v2] PCI: dwc: Add support to add GEN3 related equalization
 quirks

On Fri, Sep 13, 2019 at 11:39:50, Pankaj Dubey <pankaj.dubey@...sung.com> 
wrote:

> From: Anvesh Salveru <anvesh.s@...sung.com>
> 
> In some platforms, PCIe PHY may have issues which will prevent linkup
> to happen in GEN3 or higher speed. In case equalization fails, link will
> fallback to GEN1.
> 
> DesignWare controller gives flexibility to disable GEN3 equalization
> completely or only phase 2 and 3 of equalization.
> 
> This patch enables the DesignWare driver to disable the PCIe GEN3
> equalization by enabling one of the following quirks:
>  - DWC_EQUALIZATION_DISABLE: To disable GEN3 equalization all phases
>  - DWC_EQ_PHASE_2_3_DISABLE: To disable GEN3 equalization phase 2 & 3
> 
> Platform drivers can set these quirks via "quirk" variable of "dw_pcie"
> struct.
> 
> Signed-off-by: Anvesh Salveru <anvesh.s@...sung.com>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
> ---
> Patchset v1 can be found at:
>  - 1/2: https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2019_9_10_443&d=DwIBaQ&c=DPL6_X_6JkXFx7AXWqB0tg&r=bkWxpLoW-f-E3EdiDCCa0_h0PicsViasSlvIpzZvPxs&m=5Bl547vvEgw0xPMh4kZvKIUj2nsu5wQxtXk6lj0J0X8&s=r0J-EATorWbw9L2P4gG0zUt1jqKDCyYY7B5zcZutnP0&e= 
>  - 2/2: https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2019_9_10_444&d=DwIBaQ&c=DPL6_X_6JkXFx7AXWqB0tg&r=bkWxpLoW-f-E3EdiDCCa0_h0PicsViasSlvIpzZvPxs&m=5Bl547vvEgw0xPMh4kZvKIUj2nsu5wQxtXk6lj0J0X8&s=Ii2svOQQzPyci6Gztr3_-RlCe_Fzv-lCavUYhHwZvbA&e= 
> 
> Changes w.r.t v1:
>  - Squashed two patches from v1 into one as suggested by Gustavo
>  - Addressed review comments from Andrew
> 
>  drivers/pci/controller/dwc/pcie-designware.c | 12 ++++++++++++
>  drivers/pci/controller/dwc/pcie-designware.h |  9 +++++++++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 7d25102..97fb18d 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -466,4 +466,16 @@ void dw_pcie_setup(struct dw_pcie *pci)
>  		break;
>  	}
>  	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> +
> +	if (pci->quirk & DWC_EQUALIZATION_DISABLE) {
> +		val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> +		val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> +		dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> +	}
> +
> +	if (pci->quirk & DWC_EQ_PHASE_2_3_DISABLE) {
> +		val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> +		val |= PORT_LOGIC_GEN3_EQ_PHASE_2_3_DISABLE;
> +		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 ffed084..e428b62 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -29,6 +29,10 @@
>  #define LINK_WAIT_MAX_IATU_RETRIES	5
>  #define LINK_WAIT_IATU			9
>  
> +/* Parameters for GEN3 related quirks */
> +#define DWC_EQUALIZATION_DISABLE	BIT(1)
> +#define DWC_EQ_PHASE_2_3_DISABLE	BIT(2)
> +
>  /* Synopsys-specific PCIe configuration registers */
>  #define PCIE_PORT_LINK_CONTROL		0x710
>  #define PORT_LINK_MODE_MASK		GENMASK(21, 16)
> @@ -60,6 +64,10 @@
>  #define PCIE_MSI_INTR0_MASK		0x82C
>  #define PCIE_MSI_INTR0_STATUS		0x830
>  
> +#define PCIE_PORT_GEN3_RELATED		0x890
> +#define PORT_LOGIC_GEN3_EQ_PHASE_2_3_DISABLE	BIT(9)
> +#define PORT_LOGIC_GEN3_EQ_DISABLE		BIT(16)
> +
>  #define PCIE_ATU_VIEWPORT		0x900
>  #define PCIE_ATU_REGION_INBOUND		BIT(31)
>  #define PCIE_ATU_REGION_OUTBOUND	0
> @@ -244,6 +252,7 @@ struct dw_pcie {
>  	struct dw_pcie_ep	ep;
>  	const struct dw_pcie_ops *ops;
>  	unsigned int		version;
> +	unsigned int		quirk;
>  };
>  
>  #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)
> -- 
> 2.7.4


Acked-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>