linux-kernel - RE: [PATCH] clk: clk-fixed-factor: Use new macro CLK_OF_DECLARE

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Date:   Fri, 01 Jun 2018 23:40:36 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Rajan Vaja <RAJANV@...inx.com>
Cc:     "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jolly Shah <JOLLYS@...inx.com>,
        Michal Simek <michals@...inx.com>,
        "mturquette@...libre.com" <mturquette@...libre.com>
Subject: RE: [PATCH] clk: clk-fixed-factor: Use new macro CLK_OF_DECLARE_DRIVER

Quoting Rajan Vaja (2018-05-03 02:18:30)
> Hi Stephen,
> 
> > -----Original Message-----
> > From: Rajan Vaja
> > Sent: 16 March 2018 05:20 PM
> > To: 'Stephen Boyd' <sboyd@...nel.org>
> > Cc: linux-clk@...r.kernel.org; linux-kernel@...r.kernel.org; Jolly Shah
> > <JOLLYS@...inx.com>; Michal Simek <michals@...inx.com>;
> > mturquette@...libre.com
> > Subject: RE: [PATCH] clk: clk-fixed-factor: Use new macro
> > CLK_OF_DECLARE_DRIVER
> > 
> > Hi Stephen,
> > 
> > Thanks for the comment.
> > 
> > > -----Original Message-----
> > > From: Stephen Boyd [mailto:sboyd@...nel.org]
> > > Sent: 16 March 2018 12:17 AM
> > > To: Rajan Vaja <RAJANV@...inx.com>
> > > Cc: linux-clk@...r.kernel.org; linux-kernel@...r.kernel.org; Jolly Shah
> > > <JOLLYS@...inx.com>; Michal Simek <michals@...inx.com>;
> > > mturquette@...libre.com
> > > Subject: RE: [PATCH] clk: clk-fixed-factor: Use new macro
> > > CLK_OF_DECLARE_DRIVER
> > >
> > > Quoting Rajan Vaja (2018-03-09 11:27:40)
> > > > > From: Stephen Boyd [mailto:sboyd@...nel.org]
> > > > >
> > > > > Is the intent to register the clk twice? I believe things are working as
> > > > > intended without this patch, so maybe you can explain a little more what
> > > > > you're trying to fix.
> > > > [Rajan] Yes. During of_clk_init() if some DT fixed factor clock has
> > > > parent which is neither mentioned in output-clock-names of clock
> > > > controller nor registered as clock provider, of_clk_init() will try to
> > > > forcefully register in second loop.
> > > >
> > > >                         if (force || parent_ready(clk_provider->np)) {
> > > >
> > > >                                 /* Don't populate platform devices */
> > > >                                 of_node_set_flag(clk_provider->np,
> > > >                                                  OF_POPULATED);
> > > >
> > > > So registration of this DT fixed-factor clock would fail as parent
> > > > would be NULL as below (called from _of_fixed_factor_clk_setup()):
> > > > parent_name = of_clk_get_parent_name(node, 0);
> > > >
> > > > On the other hand, even if registration failed, that node will be
> > > > marked as OF_POPULATED, so probe of clk-fixed-factor.c will also not
> > > > be called and that DT fixed-factor clock would never be registered.
> > > >
> > > > Same thing is discussed at  https://lkml.org/lkml/2017/6/5/681 .
> > >
> > > Ok. I believe the answer is to fix the DT to describe the parent chain
> > > properly with clock-output-names. Otherwise, we have no good way of
> > > figuring out what the name should be.
> > [Rajan] clock DT binding doc says that clock-output-names property
> > is optional and sometimes not recommended.
> > I think this patch fixes the issue we have which mandates to add clock-output-
> > names
> > property (for this particular case). Also, IIUC platform driver probe in clk-fixed-
> > factor.c
> > will never be called unless we use CLK_OF_DECLARE_DRIVER.
> > I completely agree that proper solution would be to stop using strings to
> > describe clock topology.
> [Rajan] Any comments on this?
> Unless we have proper solution ready, we need to have some mechanism to handle this scenario.
> clock-output-names is optional and without this, it mandates to use clock-output-names.
> 

I couldn't read your outlook sent email and I was too busy to go
translate it. Some bug in my MUA it seems.

Can you add the output-names property? In this case it's practically
mandatory, so if you can't do it I'd like to hear why not.