Re: [PATCH] PCI: imx6: fix occasional link failure

[Bjorn Helgaas <bhelgaas@google.com>]

On Thu, Aug 07, 2014 at 11:36:40PM -0700, Tim Harvey wrote:
> According to the IMX6 reference manuals, REF_SSP_EN (Reference clock enable
> for SS function) must remain deasserted until the reference clock is running
> at the appropriate frequency.
> 
> Without this patch we find a high link failure rate (>5%) on certain
> IMX6 boards at various temperatures.
> 
> Signed-off-by: Tim Harvey <tharvey@gateworks.com>

Applied to pci/host-imx6 for v3.18 with acks from Marek and Lucas, thanks!

> ---
>  drivers/pci/host/pci-imx6.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index 1be6073..9b6bab9 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -256,11 +256,6 @@ static int imx6_pcie_deassert_core_reset(struct pcie_port *pp)
>  	struct imx6_pcie *imx6_pcie = to_imx6_pcie(pp);
>  	int ret;
>  
> -	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
> -			IMX6Q_GPR1_PCIE_TEST_PD, 0 << 18);
> -	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
> -			IMX6Q_GPR1_PCIE_REF_CLK_EN, 1 << 16);
> -
>  	ret = clk_prepare_enable(imx6_pcie->pcie_phy);
>  	if (ret) {
>  		dev_err(pp->dev, "unable to enable pcie_phy clock\n");
> @@ -282,6 +277,12 @@ static int imx6_pcie_deassert_core_reset(struct pcie_port *pp)
>  	/* allow the clocks to stabilize */
>  	usleep_range(200, 500);
>  
> +	/* power up core phy and enable ref clock */
> +	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
> +			IMX6Q_GPR1_PCIE_TEST_PD, 0 << 18);
> +	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
> +			IMX6Q_GPR1_PCIE_REF_CLK_EN, 1 << 16);
> +
>  	/* Some boards don't have PCIe reset GPIO. */
>  	if (gpio_is_valid(imx6_pcie->reset_gpio)) {
>  		gpio_set_value(imx6_pcie->reset_gpio, 0);
> -- 
> 1.8.3.2
>