Re: [PATCH] OMAP2/3/4: DMA: reset controller during init

[Tony Lindgren <tony@atomide.com>]

* Kevin Hilman <khilman@deeprootsystems.com> [100503 11:19]:
> Tony Lindgren <tony@atomide.com> writes:
> 
> > * Kevin Hilman <khilman@deeprootsystems.com> [100503 10:00]:
> >> Tony Lindgren <tony@atomide.com> writes:
> >> 
> >> > * Kevin Hilman <khilman@deeprootsystems.com> [100503 08:58]:
> >> >> Mika Westerberg <ext-mika.1.westerberg@nokia.com> writes:
> >> >> 
> >> >> > If we are softbooting another kernel using kexec, DMA controller state is not
> >> >> > known when we are performing omap_init_dma(). It is possible that some DMA
> >> >> > channels are already active. For example after kexec we get:
> >> >> >
> >> >> > <4>IRQ 0020 for non-allocated DMAchannel 5
> >> >> > <4>IRQ 0020 for non-allocated DMAchannel 5
> >> >> > <4>IRQ 0020 for non-allocated DMAchannel 5
> >> >> > <4>IRQ 0020 for non-allocated DMAchannel 5
> >> >> > <4>IRQ 0020 for non-allocated DMAchannel 5
> >> >> >
> >> >> > To prevent any weird things happening, we perform soft reset for the controller
> >> >> > and disable all per channel interrupts.
> >> >> >
> >> >> > Signed-off-by: Mika Westerberg <ext-mika.1.westerberg@nokia.com>
> >> >> 
> >> >> This is a good fix, but we get reset of DMA (and all other blocks) for
> >> >> free when switching to hwmod.  Here's a good reason to convert DMA
> >> >> to hwmod.
> >> >
> >> > Hmm, do we have existing DMA hwmod patches somewhere that work on all omaps?
> >> 
> >> No, that's my point. 
> >> 
> >> Rather than implement reset here (then remove it with DMA hwmods) I'd
> >> rather just see a DMA hwmods added, and then we get reset for free.
> >
> > Sure. But until we have something available we should get the fix part in.
> 
> which will reduce the likelyhood of anyone doing the DMA hwmods until
> some sucker like me does it since nobody else will. :(

Yeah I feel your pain.

Anyways, doing that hwmod change is too late for this coming merge
window if we don't have the patches ready. So we still need to fix
the problem.
 
> I'm just looking for more ways to motivate others to help in hwmod
> conversion.

Yes, and in addition to that at least plat-omap/dma.c, plat-omap/gpio.c
could use some serious clean-up.. And i2c-omap.c too.

Tony