linux-kernel - Re: [PATCH/RFC 2/2] arm/tegra: add timeout to PCIe PLL lock detection loop

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Date:	Tue, 6 Mar 2012 10:38:12 +0100
From:	Andi <andi.shyti@...il.com>
To:	Dmitry Artamonow <mad_soft@...ox.ru>
Cc:	linux-tegra@...r.kernel.org, Colin Cross <ccross@...roid.com>,
	Olof Johansson <olof@...om.net>,
	Stephen Warren <swarren@...dia.com>,
	Mike Rapoport <mike@...pulab.co.il>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC 2/2] arm/tegra: add timeout to PCIe PLL lock detection loop

Hi,

On Tue, Mar 6, 2012 at 9:45 AM, Dmitry Artamonow <mad_soft@...ox.ru> wrote:
> Tegra PCIe driver waits for PLL to lock using busy loop.
> If PLL fails to lock for some reason, this leads to silent lockup
> while booting (as PCIe code is not modular).
>
> Fix by adding timeout, so if PLL doesn't lock in a couple
> of seconds, just PCIe driver fails and machine continues to boot.
>
> Signed-off-by: Dmitry Artamonow <mad_soft@...ox.ru>
> ---
>  arch/arm/mach-tegra/pcie.c |   14 +++++++++++---
>  1 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/mach-tegra/pcie.c b/arch/arm/mach-tegra/pcie.c
> index 14b29ab..ffdfdd4 100644
> --- a/arch/arm/mach-tegra/pcie.c
> +++ b/arch/arm/mach-tegra/pcie.c
> @@ -585,10 +585,10 @@ static void tegra_pcie_setup_translations(void)
>        afi_writel(0, AFI_MSI_BAR_SZ);
>  }
>
> -static void tegra_pcie_enable_controller(void)
> +static int tegra_pcie_enable_controller(void)
>  {
>        u32 val, reg;
> -       int i;
> +       int i, timeout;
>
>        /* Enable slot clock and pulse the reset signals */
>        for (i = 0, reg = AFI_PEX0_CTRL; i < 2; i++, reg += 0x8) {
> @@ -639,8 +639,14 @@ static void tegra_pcie_enable_controller(void)
>        pads_writel(0xfa5cfa5c, 0xc8);
>
>        /* Wait for the PLL to lock */
> +       timeout = 2000;
>        do {
>                val = pads_readl(PADS_PLL_CTL);
> +               mdelay(1);

why are you using an mdelay? If you need to sleep 1ms just use
usleep_range or similar

Andi

> +               if (--timeout == 0) {
> +                       pr_err("Tegra PCIe error: timeout waiting for PLL\n");
> +                       return -EBUSY;
> +               }
>        } while (!(val & PADS_PLL_CTL_LOCKDET));
>
>        /* turn off IDDQ override */
> @@ -921,7 +927,9 @@ int __init tegra_pcie_init(bool init_port0, bool init_port1)
>        if (err)
>                return err;
>
> -       tegra_pcie_enable_controller();
> +       err = tegra_pcie_enable_controller();
> +       if (err)
> +               return err;
>
>        /* setup the AFI address translations */
>        tegra_pcie_setup_translations();
> --
> 1.7.5.1.300.gc565c
>
> --
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