linux-kernel - RE: [PATCH v5 4/5] fsl_pmc: Add API to enable device as wakeup event source

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Message-ID: <94F013E7935FF44C83EBE7784D62AD3F09335D27@039-SN2MPN1-022.039d.mgd.msft.net>
Date:	Tue, 5 Jun 2012 04:08:25 +0000
From:	Li Yang-R58472 <r58472@...escale.com>
To:	Wood Scott-B07421 <B07421@...escale.com>,
	Zhao Chenhui-B35336 <B35336@...escale.com>
CC:	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"galak@...nel.crashing.org" <galak@...nel.crashing.org>
Subject: RE: [PATCH v5 4/5] fsl_pmc: Add API to enable device as wakeup
 event source



> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Tuesday, June 05, 2012 7:03 AM
> To: Zhao Chenhui-B35336
> Cc: linuxppc-dev@...ts.ozlabs.org; linux-kernel@...r.kernel.org;
> galak@...nel.crashing.org; Li Yang-R58472
> Subject: Re: [PATCH v5 4/5] fsl_pmc: Add API to enable device as wakeup
> event source
> 
> On 06/04/2012 06:36 AM, Zhao Chenhui wrote:
> > On Fri, Jun 01, 2012 at 05:08:52PM -0500, Scott Wood wrote:
> >> On 05/11/2012 06:53 AM, Zhao Chenhui wrote:
> >>> Add APIs for setting wakeup source and lossless Ethernet in low power
> modes.
> >>> These APIs can be used by wake-on-packet feature.
> >>>
> >>> Signed-off-by: Dave Liu <daveliu@...escale.com>
> >>> Signed-off-by: Li Yang <leoli@...escale.com>
> >>> Signed-off-by: Jin Qing <b24347@...escale.com>
> >>> Signed-off-by: Zhao Chenhui <chenhui.zhao@...escale.com>
> >>> ---
> >>>  arch/powerpc/sysdev/fsl_pmc.c |   71
> ++++++++++++++++++++++++++++++++++++++++-
> >>>  arch/powerpc/sysdev/fsl_soc.h |    9 +++++
> >>>  2 files changed, 79 insertions(+), 1 deletions(-)
> >>>
> >>> diff --git a/arch/powerpc/sysdev/fsl_pmc.c
> b/arch/powerpc/sysdev/fsl_pmc.c
> >>> index 1dc6e9e..c1170f7 100644
> >>> --- a/arch/powerpc/sysdev/fsl_pmc.c
> >>> +++ b/arch/powerpc/sysdev/fsl_pmc.c
> >>> @@ -34,6 +34,7 @@ struct pmc_regs {
> >>>  	__be32 powmgtcsr;
> >>>  #define POWMGTCSR_SLP		0x00020000
> >>>  #define POWMGTCSR_DPSLP		0x00100000
> >>> +#define POWMGTCSR_LOSSLESS	0x00400000
> >>>  	__be32 res3[2];
> >>>  	__be32 pmcdr;
> >>>  };
> >>> @@ -43,6 +44,74 @@ static unsigned int pmc_flag;
> >>>
> >>>  #define PMC_SLEEP	0x1
> >>>  #define PMC_DEEP_SLEEP	0x2
> >>> +#define PMC_LOSSLESS	0x4
> >>> +
> >>> +/**
> >>> + * mpc85xx_pmc_set_wake - enable devices as wakeup event source
> >>> + * @pdev: platform device affected
> >>> + * @enable: True to enable event generation; false to disable
> >>> + *
> >>> + * This enables the device as a wakeup event source, or disables it.
> >>> + *
> >>> + * RETURN VALUE:
> >>> + * 0 is returned on success
> >>> + * -EINVAL is returned if device is not supposed to wake up the
> system
> >>> + * Error code depending on the platform is returned if both the
> platform and
> >>> + * the native mechanism fail to enable the generation of wake-up
> events
> >>> + */
> >>> +int mpc85xx_pmc_set_wake(struct platform_device *pdev, bool enable)
> >>
> >> Why does it have to be a platform_device?  Would a bare device_node
> work
> >> here?  If it's for stuff like device_may_wakeup() that could be in a
> >> platform_device wrapper function.
> >
> > It does not have to be a platform_device. I think it can be a struct
> device.
> 
> Why does it even need that?  The low level mechanism for influencing
> PMCDR should only need a device node, not a Linux device struct.

It does no harm to pass the device structure and makes more sense for object oriented interface design. 

> 
> >> Where does this get called from?  I don't see an example user in this
> >> patchset.
> >
> > It will be used by a gianfar related patch. I plan to submit that patch
> > after these patches accepted.
> 
> It would be nice to see how this is used when reviewing this.
> 
> >>> +{
> >>> +	int ret = 0;
> >>> +	struct device_node *clk_np;
> >>> +	u32 *prop;
> >>> +	u32 pmcdr_mask;
> >>> +
> >>> +	if (!pmc_regs) {
> >>> +		pr_err("%s: PMC is unavailable\n", __func__);
> >>> +		return -ENODEV;
> >>> +	}
> >>> +
> >>> +	if (enable && !device_may_wakeup(&pdev->dev))
> >>> +		return -EINVAL;
> >>
> >> Who is setting can_wakeup for these devices?
> >
> > The device driver is responsible to set can_wakeup.
> 
> How would the device driver know how to set it?  Wouldn't this depend on
> the particular SoC and low power mode?

It is based on the "fsl,magic-packet" and "fsl,wake-on-filer" device tree properties.

Leo

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