linux-kernel - Re: [PATCH v7 4/4] PCI: imx6: Do not switch speed if Gen2 is disabled

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Date:   Tue, 21 Mar 2017 14:51:57 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Andrey Smirnov <andrew.smirnov@...il.com>
Cc:     linux-pci@...r.kernel.org, yurovsky@...il.com,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Fabio Estevam <fabio.estevam@....com>,
        Dong Aisheng <dongas86@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 4/4] PCI: imx6: Do not switch speed if Gen2 is
 disabled

Am Dienstag, den 21.03.2017, 06:42 -0700 schrieb Andrey Smirnov:
> Save a bit of time and avoid going through link speed change procedure
> in configuration where link max speed is limited to Gen1 in DT.
> 
> Cc: yurovsky@...il.com
> Cc: Lucas Stach <l.stach@...gutronix.de>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Fabio Estevam <fabio.estevam@....com>
> Cc: Dong Aisheng <dongas86@...il.com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>

Reviewed-by: Lucas Stach <l.stach@...gutronix.de>

> ---
>  drivers/pci/dwc/pci-imx6.c | 52 +++++++++++++++++++++++-----------------------
>  1 file changed, 26 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/pci/dwc/pci-imx6.c b/drivers/pci/dwc/pci-imx6.c
> index c731e41..9407c03 100644
> --- a/drivers/pci/dwc/pci-imx6.c
> +++ b/drivers/pci/dwc/pci-imx6.c
> @@ -533,40 +533,40 @@ static int imx6_pcie_establish_link(struct imx6_pcie *imx6_pcie)
>  		tmp &= ~PCIE_RC_LCR_MAX_LINK_SPEEDS_MASK;
>  		tmp |= PCIE_RC_LCR_MAX_LINK_SPEEDS_GEN2;
>  		dw_pcie_writel_dbi(pci, PCIE_RC_LCR, tmp);
> -	} else {
> -		dev_info(dev, "Link: Gen2 disabled\n");
> -	}
> -
> -	/*
> -	 * Start Directed Speed Change so the best possible speed both link
> -	 * partners support can be negotiated.
> -	 */
> -	tmp = dw_pcie_readl_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL);
> -	tmp |= PORT_LOGIC_SPEED_CHANGE;
> -	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, tmp);
>  
> -	if (imx6_pcie->variant != IMX7D) {
>  		/*
> -		 * On i.MX7, DIRECT_SPEED_CHANGE behaves differently
> -		 * from i.MX6 family when no link speed transition
> -		 * occurs and we go Gen1 -> yep, Gen1. The difference
> -		 * is that, in such case, it will not be cleared by HW
> -		 * which will cause the following code to report false
> -		 * failure.
> +		 * Start Directed Speed Change so the best possible
> +		 * speed both link partners support can be negotiated.
>  		 */
> +		tmp = dw_pcie_readl_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL);
> +		tmp |= PORT_LOGIC_SPEED_CHANGE;
> +		dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, tmp);
> +
> +		if (imx6_pcie->variant != IMX7D) {
> +			/*
> +			 * On i.MX7, DIRECT_SPEED_CHANGE behaves differently
> +			 * from i.MX6 family when no link speed transition
> +			 * occurs and we go Gen1 -> yep, Gen1. The difference
> +			 * is that, in such case, it will not be cleared by HW
> +			 * which will cause the following code to report false
> +			 * failure.
> +			 */
> +
> +			ret = imx6_pcie_wait_for_speed_change(imx6_pcie);
> +			if (ret) {
> +				dev_err(dev, "Failed to bring link up!\n");
> +				goto err_reset_phy;
> +			}
> +		}
>  
> -		ret = imx6_pcie_wait_for_speed_change(imx6_pcie);
> +		/* Make sure link training is finished as well! */
> +		ret = imx6_pcie_wait_for_link(imx6_pcie);
>  		if (ret) {
>  			dev_err(dev, "Failed to bring link up!\n");
>  			goto err_reset_phy;
>  		}
> -	}
> -
> -	/* Make sure link training is finished as well! */
> -	ret = imx6_pcie_wait_for_link(imx6_pcie);
> -	if (ret) {
> -		dev_err(dev, "Failed to bring link up!\n");
> -		goto err_reset_phy;
> +	} else {
> +		dev_info(dev, "Link: Gen2 disabled\n");
>  	}
>  
>  	tmp = dw_pcie_readl_dbi(pci, PCIE_RC_LCSR);