Subject: [PATCH] PCI: imx6: Fix link_up detection

From: [email-masked] (Marek Vasut)
Date: Wed, 12 Feb 2014 08:36:16 +0100

On Wednesday, February 12, 2014 at 08:27:55 AM, Sascha Hauer wrote:

+CC Troy Kisky, since I think he submitted something similar some time ago 
already.

Otherwise I agree this happens.

> This is broken since:
> | commit e6daf4a5e1b813bc7f85507ec83b8c2452c121e6
> | Author: Marek Vasut <[email-masked]>
> | Date:   Thu Dec 12 22:49:59 2013 +0100
> | 
> |     PCI: imx6: Report "link up" only after link training completes
> |     
> |     While waiting for the PHY to report the PCIe link is up, we might hit
> |     a situation where the link training is still in progress, while the
> |     PHY already reports the link is up.  Add additional check for this
> |     condition.
> |     
> |     Signed-off-by: Marek Vasut <[email-masked]>
> |     Signed-off-by: Bjorn Helgaas <[email-masked]>
> |     Acked-by: Shawn Guo <[email-masked]>
> 
> The problem is: Before the above commit only the
> PCIE_PHY_DEBUG_R1_XMLH_LINK_UP bit was used to determine whether the link
> is up or not. Since the above commit also the
> PCIE_PHY_DEBUG_R1_XMLH_LINK_IN_TRAINING is used. This means a link still
> being trained is as link down.
> The designware driver changes the PORT_LOGIC_SPEED_CHANGE bit in
> dw_pcie_host_init() which causes the link to be retrained. During the next
> call to dw_pcie_rd_conf() the link is then reported being down and the
> function returns PCIBIOS_DEVICE_NOT_FOUND resulting in nonfunctioning
> PCIe.
> 
> This patch fixes this by waiting until the link training has finished
> before testing the PCIE_PHY_DEBUG_R1_XMLH_LINK_UP bit. This is hardly the
> correct solution, but I don't know what should be done instead.
> 
> Signed-off-by: Sascha Hauer <[email-masked]>
> Cc: Richard Zhu <[email-masked]> (maintainer:PCI DRIVER FOR IMX6)
> Cc: Shawn Guo <[email-masked]> (maintainer:PCI DRIVER FOR IMX6)
> Cc: Bjorn Helgaas <[email-masked]> (supporter:PCI SUBSYSTEM)
> Cc: linux-pci at vger.kernel.org
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: Marek Vasut <[email-masked]>
> ---
>  drivers/pci/host/pci-imx6.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index 866bdc7..9b6b501 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -449,6 +449,7 @@ static void imx6_pcie_reset_phy(struct pcie_port *pp)
>  static int imx6_pcie_link_up(struct pcie_port *pp)
>  {
>  	u32 rc, ltssm, rx_valid;
> +	int count = 1000;
> 
>  	/*
>  	 * Test if the PHY reports that the link is up and also that
> @@ -458,8 +459,13 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
>  	 * as well here.
>  	 */
>  	rc = readl(pp->dbi_base + PCIE_PHY_DEBUG_R1);
> -	if ((rc & PCIE_PHY_DEBUG_R1_XMLH_LINK_UP) &&
> -	    !(rc & PCIE_PHY_DEBUG_R1_XMLH_LINK_IN_TRAINING))
> +	while (rc & PCIE_PHY_DEBUG_R1_XMLH_LINK_IN_TRAINING) {
> +		if (!count--)
> +			return 0;
> +		rc = readl(pp->dbi_base + PCIE_PHY_DEBUG_R1);
> +	}
> +
> +	if (rc & PCIE_PHY_DEBUG_R1_XMLH_LINK_UP)
>  		return 1;
> 
>  	/*