Re: [PATCH/RFC 1/2] simple SPI framework

[Adam Belay <ambx1@neo.rr.com>]

On Wed, Oct 05, 2005 at 12:06:37PM +0400, Vitaly Wool wrote:
> David,
> 
> >+#ifdef	CONFIG_PM
> >+
> >+/* Suspend/resume in "struct device_driver" don't really need that
> >+ * strange third parameter, so we just make it a constant and expect
> >+ * SPI drivers to ignore it just like most platform drivers do.
> >+ *
> > 
> >
> So you just ignored my letter on that subject :(
> The fact that you don't need it doesn't mean that other people won't.
> The fact that there's no clean way to suspend USB doesn't mean that 
> there shouldn't be one for SPI.
> 
> >+ * NOTE:  the suspend() method for an spi_master controller driver
> >+ * should verify that all its child devices are marked as suspended;
> >+ * suspend requests delivered through sysfs power/state files don't
> >+ * enforce such constraints.

But we should, right?  It seems like a child device should never be in a
higher suspend state than its parents.  The rule doesn't have to hold with
driver-initiated runtime power management, but when the user requests a
suspend via power/state, it's reasonable to assume every child should
be suspended first.

> >+ */
> >+static int spi_suspend(struct device *dev, pm_message_t message)
> >+{
> >+	int	value;
> >+
> >+	if (!dev->driver || !dev->driver->suspend)
> >+		return 0;
> >+
> >+	/* suspend will stop irqs and dma; no more i/o */
> >+	value = dev->driver->suspend(dev, message, SUSPEND_POWER_DOWN);
> > 
> >
> So driver->suspend is going to be called 3 timer with SUSPEND_POWER_DOWN 
> parameter, right?
> I'm afraid that won't work :(
> Especially in our case, where we *do need* preparation steps that are 
> taken in *normal* suspend sequence - i. e. we need to set up the wakeup 
> credentials for the *SPI* since the wakeup's gonna happen from a call 
> incoming through the network module residing on the SPI bus!

So...

1.) suspend all child devices
2.) calculate their wake requirements
3.) suspend the parent to a degree compatible with those requirements

Right?

Thanks,
Adam