[PATCH] ARM: mx6: Fix suspend/resume with PCI

[Bjørn Erik Nilsen]

Hi Fabio,

On Wed, 2014-08-06 at 21:39 -0300, an unknown sender wrote:
> From: Fabio Estevam <fabio.estevam at freescale.com>
> 
> When PCI is used and a suspend/resume sequence is done we see the following
> kernel hang:
> 
> root at freescale /$ echo mem > /sys/power/state 
> [   16.099018] PM: Syncing filesystems ... done.
> [   16.141010] Freezing user space processes ... (elapsed 0.002 seconds) done.
> [   16.150840] Freezing remaining freezable tasks ... (elapsed 0.003 seconds) done.
> [   16.199438] random: nonblocking pool is initialized
> [   16.229639] PM: suspend of devices complete after 64.793 msecs
> [   16.235488] PM: suspend devices took 0.070 seconds
> [   16.245301] PM: late suspend of devices complete after 4.968 msecs
> [   16.257063] PM: noirq suspend of devices complete after 5.538 msecs
> [   16.263425] Disabling non-boot CPUs ...
> [   16.274666] CPU1: shutdown
> [   16.286351] CPU2: shutdown
> [   16.294169] CPU3: shutdown
> [   16.299551] Enabling non-boot CPUs ...
> [   16.304155] CPU1: Booted secondary processor
> [   16.305717] CPU1 is up
> [   16.313078] CPU2: Booted secondary processor
> [   16.313456] CPU2 is up
> [   16.320778] CPU3: Booted secondary processor
> [   16.321174] CPU3 is up
> 	(hangs here)
> 
> Implement a workaround for the erratum ERR005723: "PCIe does not support L2
> Power Down", which consists in toggling bit 18 (TEST_POWERDOWN) of GPR1 register.
> 
> Tested on a mx6qsabresd TO1.2 revC2.
> 
> Reported-by: Shawn Guo <shawn.guo at freescale.com>
> Signed-off-by: Fabio Estevam <fabio.estevam at freescale.com>

Tested-by: Bjørn Erik Nilsen <ben at datarespons.no>

I encountered exactly the same problem and can confirm your patch works.

Thank you!

I hope this patch (or one that is considered a proper solution) will
make it to the mainline kernel any time soon.


Best regards,
Bjørn Erik Nilsen

> ---
> Richard,
> 
> Is there any better method to fix this issue? Or should we do the same
> as in the FSL kernel?
> 
> I also tried to add pm ops into the imx6 pci driver and did the toggle there,
> but I still got the kernel hang.
> 
>  arch/arm/mach-imx/pm-imx6.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/arch/arm/mach-imx/pm-imx6.c b/arch/arm/mach-imx/pm-imx6.c
> index 5c3af8f..92511cf 100644
> --- a/arch/arm/mach-imx/pm-imx6.c
> +++ b/arch/arm/mach-imx/pm-imx6.c
> @@ -341,6 +341,23 @@ static int imx6q_suspend_finish(unsigned long val)
>  
>  static int imx6q_pm_enter(suspend_state_t state)
>  {
> +	struct regmap *gpr;
> +	gpr = syscon_regmap_lookup_by_compatible("fsl,imx6q-iomuxc-gpr");
> +	if (IS_ERR(gpr)) {
> +		pr_err("failed to find fsl,imx6q-iomux-gpr regmap\n");
> +		return PTR_ERR(gpr);
> +	}
> +
> +	/*
> +	 * L2 can exit by 'reset' or Inband beacon (from remote EP)
> +	 * toggling phy_powerdown has same effect as 'inband beacon'
> +	 * So, toggle bit18 of GPR1 as a workaround of erratum
> +	 * ERR005723 - "PCIe does not support L2 Power Down"
> +	 */
> +	if (IS_ENABLED(CONFIG_PCI_IMX6) && !cpu_is_imx6sx())
> +		regmap_update_bits(gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_TEST_PD,
> +				   IMX6Q_GPR1_PCIE_TEST_PD);
> +
>  	switch (state) {
>  	case PM_SUSPEND_STANDBY:
>  		imx6q_set_lpm(STOP_POWER_ON);
> @@ -383,6 +400,16 @@ static int imx6q_pm_enter(suspend_state_t state)
>  		return -EINVAL;
>  	}
>  
> +	/*
> +	 * L2 can exit by 'reset' or Inband beacon (from remote EP)
> +	 * toggling phy_powerdown has same effect as 'inband beacon'
> +	 * So, toggle bit18 of GPR1 as a workaround of erratum
> +	 * ERR005723 - "PCIe does not support L2 Power Down"
> +	 */
> +	if (IS_ENABLED(CONFIG_PCI_IMX6) && !cpu_is_imx6sx())
> +		regmap_update_bits(gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_TEST_PD,
> +				   !IMX6Q_GPR1_PCIE_TEST_PD);
> +
>  	return 0;
>  }
>