Messages in this thread | | | From | Rajan Vaja <> | Subject | RE: [PATCH] clk: clk-fixed-factor: Use new macro CLK_OF_DECLARE_DRIVER | Date | Thu, 3 May 2018 09:18:30 +0000 |
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Hi Stephen,
> -----Original Message----- > From: Rajan Vaja > Sent: 16 March 2018 05:20 PM > To: 'Stephen Boyd' <sboyd@kernel.org> > Cc: linux-clk@vger.kernel.org; linux-kernel@vger.kernel.org; Jolly Shah > <JOLLYS@xilinx.com>; Michal Simek <michals@xilinx.com>; > mturquette@baylibre.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@kernel.org] > > Sent: 16 March 2018 12:17 AM > > To: Rajan Vaja <RAJANV@xilinx.com> > > Cc: linux-clk@vger.kernel.org; linux-kernel@vger.kernel.org; Jolly Shah > > <JOLLYS@xilinx.com>; Michal Simek <michals@xilinx.com>; > > mturquette@baylibre.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@kernel.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.
> > > > > The alternative is to start working on a solution for having the clk > > framework stop using strings to describe clk topology. My plan there is > > to allow clk registration to indicate that another parent names array > > should be used with clk_get() of the device or node pointer that's > > associated with the clk during registration to find the parent . If we > > had that, then we could hook up clks into the tree by calling clk_get() > > in the framework and map through the clock-names property. This also > > gets us to a point where clk names don't have to be globally unique, > > which would be nice.
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