Re: [PATCH] PCI: don't power-off apple thunderbolt controller on s2idle

[Bjorn Helgaas <helgaas@kernel.org>]

[+cc Rafael, Andreas, linux-pm]

On Thu, May 06, 2021 at 08:38:20PM +0300, Konstantin Kharlamov wrote:
> On Macbook 2013 resuming from s2idle results in external monitor no
> longer being detected, and dmesg having errors like:
> 
>     pcieport 0000:06:00.0: can't change power state from D3hot to D0 (config space inaccessible)
> 
> and a stacktrace. The reason turned out that the hw that the quirk
> powers off does not get powered on back on resume.

quirk_apple_poweroff_thunderbolt() was added in 2014 by 1df5172c5c25
("PCI: Suspend/resume quirks for Apple thunderbolt").  It claims
"power is automatically restored before resume," so there must be
something special about s2idle that prevents the power-on.

IIUC this change will reduce the s2idle power savings.  I would feel
better about this if we understood what the difference was.  

> Thus, add a check for s2idle to the quirk, and do nothing if the suspend
> mode is s2idle.

Obviously the *hardware* hasn't changed since 1df5172c5c25.  Is s2idle
something that wasn't tested back then, or is this problem connected
to an s2idle change since then?  Can we identify a commit that
introduced this problem?  That would help with backporting or stable
tags.

> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212767

Thanks for this!  Would you mind attaching the output of
"sudo lspci -vvv"?  If you attach any other dmesg, could you
use "dmesg --color=never" so the log doesn't include all the
escape characters?

> Signed-off-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
> ---
>  drivers/pci/quirks.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 653660e3ba9e..86fedcec37e2 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -27,6 +27,7 @@
>  #include <linux/nvme.h>
>  #include <linux/platform_data/x86/apple.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/suspend.h>
>  #include <linux/switchtec.h>
>  #include <asm/dma.h>	/* isa_dma_bridge_buggy */
>  #include "pci.h"
> @@ -3646,6 +3647,13 @@ static void quirk_apple_poweroff_thunderbolt(struct pci_dev *dev)
>  		return;
>  	if (pci_pcie_type(dev) != PCI_EXP_TYPE_UPSTREAM)
>  		return;
> +
> +	/*
> +	 * If suspend mode is s2idle, power won't get restored on resume.
> +	 */
> +	if (!pm_suspend_via_firmware())
> +		return;
> +
>  	bridge = ACPI_HANDLE(&dev->dev);
>  	if (!bridge)
>  		return;
> -- 
> 2.31.1
>