linux-kernel - Re: [PATCH] PCI: Do not enable async suspend for JMicron chips

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Date:	Wed, 5 Nov 2014 11:01:15 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Chuansheng Liu <chuansheng.liu@...el.com>
Cc:	Aaron Lu <aaron.lu@...el.com>, Tejun Heo <tj@...nel.org>,
	Rafael Wysocki <rjw@...ysocki.net>, mister.freeman@...oste.net,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI: Do not enable async suspend for JMicron chips

On Tue, Nov 4, 2014 at 6:31 PM, Chuansheng Liu <chuansheng.liu@...el.com> wrote:
> The JMicron chip 361/363/368 contains one SATA controller and
> one PATA controller, they are brother-relation ship in PCI tree,
> but for powering on these both controller, we must follow the
> sequence one by one, otherwise one of them can not be powered on
> successfully.

This should mention what's broken and what problem a user would see.
This changelog sounds a lot like the one for e6b7e41cdd8c, so I don't
know if this is for a new, related problem, or what.

> So here we disable the async suspend method for Jmicron chip.
>
> Bug link:
> https://bugzilla.kernel.org/show_bug.cgi?id=81551
> https://bugzilla.kernel.org/show_bug.cgi?id=84861
>
> And we can revert the below commit after this patch is applied:
> e6b7e41(ata: Disabling the async PM for JMicron chip 363/361)
>
> Cc: stable@...r.kernel.org # 3.15+
> Acked-by: Aaron Lu <aaron.lu@...el.com>
> Signed-off-by: Chuansheng Liu <chuansheng.liu@...el.com>
> ---
>  drivers/pci/pci.c |   12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 625a4ac..53128f0 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2046,7 +2046,17 @@ void pci_pm_init(struct pci_dev *dev)
>         pm_runtime_forbid(&dev->dev);
>         pm_runtime_set_active(&dev->dev);
>         pm_runtime_enable(&dev->dev);
> -       device_enable_async_suspend(&dev->dev);
> +
> +       /*
> +        * The JMicron chip 361/363/368 contains one SATA controller and
> +        * one PATA controller, they are brother-relation ship in PCI tree,
> +        * but for powering on these both controller, we must follow the
> +        * sequence one by one, otherwise one of them can not be powered on
> +        * successfully, so here we disable the async suspend method for
> +        * Jmicron chip.
> +        */
> +       if (dev->vendor != PCI_VENDOR_ID_JMICRON)
> +               device_enable_async_suspend(&dev->dev);

I don't like littering the core PCI code with vendor tests like this.
This would be the only one, except for an ancient DECchip 21050 bridge
erratum.

And why would we want a test for *all* JMicron devices here, when you
claim the problem only affects a few specific ones?

And what's the story with the e6b7e41cdd8c ("ata: Disabling the async
PM for JMicron chip 363/361") connection?  Is something broken even
with e6b7e41cdd8c, and this is a better fix?  Or is this simply a
different way of fixing the same problem?

>         dev->wakeup_prepared = false;
>
>         dev->pm_cap = 0;
> --
> 1.7.9.5
>
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