From: bhelgaas@google•com (Bjorn Helgaas)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 1/1] pci-imx6.c: wait for retraining
Date: Wed, 19 Feb 2014 15:02:07 -0700 [thread overview]
Message-ID: <20140219220207.GB19233@google.com> (raw)
In-Reply-To: <1392841338-13527-1-git-send-email-troy.kisky@boundarydevices.com>
On Wed, Feb 19, 2014 at 01:22:18PM -0700, Troy Kisky wrote:
> From: Marek Vasut <marex@denx•de>
>
> This patch handles the case where the PCIe link is up and running, yet drops
> into the LTSSM training mode. The link spends short time in the LTSSM training
> mode, but the current code can misinterpret it as the link being stalled.
> Waiting for the LTSSM training to complete fixes the issue.
>
> Quoting Sascha, "This is broken since
> commit e6daf4a5e1b813bc7f85507ec83b8c2452c121e6
> PCI: imx6: Report "link up" only after link training completes
>
> 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."
>
> Signed-off-by: Marek Vasut <marex@denx•de>
> Tested-by: Troy Kisky <troy.kisky@boundarydevices•com>
> Tested-by: Sascha Hauer <s.hauer@pengutronix•de>
> Acked-by: Shawn Guo <shawn.guo@linaro•org>
> Signed-off-by: Troy Kisky <troy.kisky@boundarydevices•com>
Applied to pci/host-imx6 for v3.15, thanks!
I changed the SHA1 in the changelog from
e6daf4a5e1b813bc7f85507ec83b8c2452c121e6 to 7f9f40c01cce, because I think
that's what's in the upstream tree.
Bjorn
> ---
> drivers/pci/host/pci-imx6.c | 47 ++++++++++++++++++++++++++++++++-------------
> 1 file changed, 34 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index e8663a8..ee08250 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -424,20 +424,40 @@ 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;
> + u32 rc, debug_r0, rx_valid;
> + int count = 5;
>
> /*
> - * Test if the PHY reports that the link is up and also that
> - * the link training finished. It might happen that the PHY
> - * reports the link is already up, but the link training bit
> - * is still set, so make sure to check the training is done
> - * as well here.
> + * Test if the PHY reports that the link is up and also that the LTSSM
> + * training finished. There are three possible states of the link when
> + * this code is called:
> + * 1) The link is DOWN (unlikely)
> + * The link didn't come up yet for some reason. This usually means
> + * we have a real problem somewhere. Reset the PHY and exit. This
> + * state calls for inspection of the DEBUG registers.
> + * 2) The link is UP, but still in LTSSM training
> + * Wait for the training to finish, which should take a very short
> + * time. If the training does not finish, we have a problem and we
> + * need to inspect the DEBUG registers. If the training does finish,
> + * the link is up and operating correctly.
> + * 3) The link is UP and no longer in LTSSM training
> + * The link is up and operating correctly.
> */
> - 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))
> - return 1;
> -
> + while (1) {
> + rc = readl(pp->dbi_base + PCIE_PHY_DEBUG_R1);
> + if (!(rc & PCIE_PHY_DEBUG_R1_XMLH_LINK_UP))
> + break;
> + if (!(rc & PCIE_PHY_DEBUG_R1_XMLH_LINK_IN_TRAINING))
> + return 1;
> + if (!count--)
> + break;
> + dev_dbg(pp->dev, "Link is up, but still in training\n");
> + /*
> + * Wait a little bit, then re-check if the link finished
> + * the training.
> + */
> + usleep_range(1000, 2000);
> + }
> /*
> * From L0, initiate MAC entry to gen2 if EP/RC supports gen2.
> * Wait 2ms (LTSSM timeout is 24ms, PHY lock is ~5us in gen2).
> @@ -446,15 +466,16 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
> * to gen2 is stuck
> */
> pcie_phy_read(pp->dbi_base, PCIE_PHY_RX_ASIC_OUT, &rx_valid);
> - ltssm = readl(pp->dbi_base + PCIE_PHY_DEBUG_R0) & 0x3F;
> + debug_r0 = readl(pp->dbi_base + PCIE_PHY_DEBUG_R0);
>
> if (rx_valid & 0x01)
> return 0;
>
> - if (ltssm != 0x0d)
> + if ((debug_r0 & 0x3f) != 0x0d)
> return 0;
>
> dev_err(pp->dev, "transition to gen2 is stuck, reset PHY!\n");
> + dev_dbg(pp->dev, "debug_r0=%08x debug_r1=%08x\n", debug_r0, rc);
>
> imx6_pcie_reset_phy(pp);
>
> --
> 1.8.1.2
>
prev parent reply other threads:[~2014-02-19 22:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-19 20:22 [PATCH 1/1] pci-imx6.c: wait for retraining Troy Kisky
2014-02-19 22:02 ` Bjorn Helgaas [this message]
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