[PATCH v4 04/12] thermal: armada: Clarify control registers accesses

[Baruch Siach]

Hi Miquèl,

On Tue, Dec 19, 2017 at 09:08:14AM +0100, Miquel RAYNAL wrote:
> On Tue, 19 Dec 2017 07:51:54 +0200
> Baruch Siach <baruch at tkos.co.il> wrote:
> > On Tue, Dec 19, 2017 at 01:32:33AM +0100, Miquel RAYNAL wrote:
> > > On Mon, 18 Dec 2017 22:35:42 +0200
> > > Baruch Siach <baruch at tkos.co.il> wrote:  
> > > > On Mon, Dec 18, 2017 at 03:36:35PM +0100, Miquel Raynal wrote:  
> > > > > Bindings were incomplete for a long time by only exposing one of
> > > > > the two available control registers. To ease the migration to
> > > > > the full bindings (already in use for the Armada 375 SoC),
> > > > > rename the pointers for clarification. This way, it will only
> > > > > be needed to add another pointer to access the other control
> > > > > register when the time comes.
> > > > > 
> > > > > This avoids dangerous situations where the offset 0 of the
> > > > > control area can be either one register or the other depending
> > > > > on the bindings used. After this change, device trees of other
> > > > > SoCs could be migrated to the "full" bindings if they may
> > > > > benefit from features from the unaccessible register, without
> > > > > any change in the driver.
> > > > > 
> > > > > Signed-off-by: Miquel Raynal <miquel.raynal at free-electrons.com>
> > > > > Reviewed-by: Gregory CLEMENT
> > > > > <gregory.clement at free-electrons.com> ---    
> > > > 
> > > > [...]
> > > >   
> > > > > +	/*
> > > > > +	 * Legacy DT bindings only described "control1"
> > > > > register (also referred
> > > > > +	 * as "control MSB" on old documentation). New bindings
> > > > > cover
> > > > > +	 * "control0/control LSB" and "control1/control MSB"
> > > > > registers within
> > > > > +	 * the same resource, which is then of size 8 instead
> > > > > of 4.
> > > > > +	 */
> > > > > +	if (resource_size(res) == LEGACY_CONTROL_MEM_LEN) {
> > > > > +		/* ->control0 unavailable in this
> > > > > configuration */
> > > > > +		priv->control1 = control +
> > > > > LEGACY_CONTROL1_OFFSET;
> > > > > +	} else {
> > > > > +		priv->control0 = control + CONTROL0_OFFSET;
> > > > > +		priv->control1 = control + CONTROL1_OFFSET;
> > > > > +	}    
> > > > 
> > > > The needs_control0 field that you mentioned in the cover page is
> > > > missing here.  
> > > 
> > > Yes, at this point nobody actually *needs* control0 so the
> > > limitation is added with the patch that introduce ap806 support as
> > > it is the first compatible that needs both control0 and control1 to
> > > work correctly. Does this bother you?  
> > 
> > No. It is just that we agreed to have a verification here that the
> > size of the control registers resource matches the binding. I thought
> > that the needs_control0 field that you mention in the cover page is
> > meant to implement that.
> 
> That is absolutely right, but at this point in the series, the supported
> compatible strings are "marvell,armada[370|375|38x|xp]-thermal". All of
> them can use both bindings so I don't see the point to have a
> needs_control0 field in this patch. It is introduced in the next patch
> that adds support for ap806 by only supporting the new bindings
> though.

OK. Makes sense.

> > necessary. It would just make sure that no one introduces a DT with
> > the wrong resource size.
> 
> Not sure I understand what exactly you wanna check, can you
> give me an example?

I wrote that before it occurred to me that we can use the control registers 
size the distinguish between the old binding and the new one.

I still think it would be nice to add needs_control0=true to armada375_data, 
for consistency with the ap806 and cp110.

baruch

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