linux-kernel - Re: [PATCH v7 3/4] PCI: imx6: Do not wait for speed change on i.MX7

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Message-ID: <1490104240.2895.22.camel@pengutronix.de>
Date:   Tue, 21 Mar 2017 14:50:40 +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 3/4] PCI: imx6: Do not wait for speed change on i.MX7

Am Dienstag, den 21.03.2017, 06:42 -0700 schrieb Andrey Smirnov:
> As can be seen from [1]:
> 
> "...the different behavior between iMX6Q PCIe and iMX7D PCIe maybe
> caused by the different controller version.
> 
> Regarding to the DOC description, the DIRECT_SPEED_CHANGE should be
> cleared after the speed change from GEN1 to GEN2. Unfortunately, when
> GEN1 device is used, the behavior is not documented.
> 
> So, IC design guys run the simulation and
> find out the following behaviors:
> 
>      1. DIRECT_SPEED_CHANGE will be cleared in 7D after speed change
>      	from GEN1 to GEN2. This matches doc’s description
> 
>      2. set MAX link speed(PCIE_CAP_TARGET_LINK_SPEED=0x01) as GEN1 and
>      	re-run the simulation, DIRECT_SPEED_CHANGE will not be cleared;
>      	remain as 1, this matches your result, but function test is
>      	passed, so this bit should not affect the normal PCIe function.
> ..."
> 
> imx6_pcie_wait_for_speed_change will report false failures for Gen1 ->
> Gen1 speed transition, so avoid doing that check and just rely on
> imx6_pcie_wait_for_link only.
> 
> [1] https://community.nxp.com/message/867943
> 
> 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 | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/dwc/pci-imx6.c b/drivers/pci/dwc/pci-imx6.c
> index 64de9bb..c731e41 100644
> --- a/drivers/pci/dwc/pci-imx6.c
> +++ b/drivers/pci/dwc/pci-imx6.c
> @@ -545,10 +545,21 @@ static int imx6_pcie_establish_link(struct imx6_pcie *imx6_pcie)
>  	tmp |= PORT_LOGIC_SPEED_CHANGE;
>  	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, tmp);
>  
> -	ret = imx6_pcie_wait_for_speed_change(imx6_pcie);
> -	if (ret) {
> -		dev_err(dev, "Failed to bring link up!\n");
> -		goto err_reset_phy;
> +	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;
> +		}
>  	}
>  
>  	/* Make sure link training is finished as well! */