Messages in this thread Patch in this message | | | Subject | Re: [PATCH] pnp: Bypass the calling to pnp_stop_dev at suspend when there is a protocol suspend | From | Yanmin Zhang <> | Date | Mon, 06 Jan 2014 09:20:51 +0800 |
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On 二, 2013-12-24 at 09:35 +0800, shuox.liu@intel.com wrote: > From: Zhang Yanmin <yanmin.zhang@intel.com> > > pnp pnp_bus_suspend/_resume have an issue. > pnp_bus_suspend calls pnp_stop_dev to disable the device. With ACPI, > pnp_stop_dev turns off the dev usually. Then, > pnp_bus_suspend=>pnp_dev->protocol->suspend accesses the device and > suspend it again. > > pnp_bus_resume has the similar issue. > > Another issue is firmware might just provide _DIS, but no_STS method. > > The patch fixes it by adding a checking. If there is > pnp_dev->protocol->suspend, pnp_bus_suspend doesn't call pnp_stop_dev. > Do the similar thing for _resume. Rafael,
What's your idea about this patch?
We hit the issue when enabling Android on a latest tablet. After suspend-to-ram wakeup, serial console doesn't work. This serial port is bound by pnpcore driver. At suspending, static int __pnp_bus_suspend(struct device *dev, pm_message_t state) { ...
if (pnp_can_disable(pnp_dev)) { error = pnp_stop_dev(pnp_dev); if (error) return error; }
if (pnp_dev->protocol->suspend) pnp_dev->protocol->suspend(pnp_dev, state); return 0; }
pnp_stop_dev calls dev->protocol->disable. As for ACPI device, that disable callback calls _DIS. Based on ACPI spec, driver need turn off the device before disabling it by _DIS. That means, after pnp_stop_dev returns, the device is at OFF state.
Then, __pnp_bus_suspend calls pnp_dev->protocol->suspend, which continues to access the device while the device is at OFF.
Our firmware just provides _DIS for the device. There is no _STS method. Then, after wakeup, the device doesn't work.
But just like what the patch points out, pnp_dev->protocol->suspend continues to access the device while the device is at OFF. It's not safe.
The patch looks like a workaround. Another possible fix is to just delete the calling of pnp_stop_dev in function __pnp_bus_suspend, as suspend is not equal to _disable_. The deletion might be a little intrusive. That's why we sent a workaround patch to LKML.
Which one is better?
Thanks, Yanmin
> > Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com> > Signed-off-by: Liu ShuoX <shuox.liu@intel.com> > --- > drivers/pnp/driver.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/drivers/pnp/driver.c b/drivers/pnp/driver.c > index f748cc8..2512e47 100644 > --- a/drivers/pnp/driver.c > +++ b/drivers/pnp/driver.c > @@ -176,7 +176,7 @@ static int __pnp_bus_suspend(struct device *dev, pm_message_t state) > return error; > } > > - if (pnp_can_disable(pnp_dev)) { > + if (pnp_can_disable(pnp_dev) && !pnp_dev->protocol->suspend) { > error = pnp_stop_dev(pnp_dev); > if (error) > return error; > @@ -215,9 +215,7 @@ static int pnp_bus_resume(struct device *dev) > error = pnp_dev->protocol->resume(pnp_dev); > if (error) > return error; > - } > - > - if (pnp_can_write(pnp_dev)) { > + } else if (pnp_can_write(pnp_dev)) { > error = pnp_start_dev(pnp_dev); > if (error) > return error;
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