Messages in this thread | | | From | Jolly Shah <> | Subject | RE: [PATCH v6 04/11] firmware: xilinx: Add query data API | Date | Tue, 15 May 2018 20:29:15 +0000 |
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Hi Sudeep,
> -----Original Message----- > From: Sudeep Holla [mailto:sudeep.holla@arm.com] > Sent: Tuesday, May 15, 2018 2:34 AM > To: Jolly Shah <JOLLYS@xilinx.com>; ard.biesheuvel@linaro.org; > mingo@kernel.org; gregkh@linuxfoundation.org; matt@codeblueprint.co.uk; > hkallweit1@gmail.com; keescook@chromium.org; > dmitry.torokhov@gmail.com; mturquette@baylibre.com; > sboyd@codeaurora.org; michal.simek@xilinx.com; robh+dt@kernel.org; > mark.rutland@arm.com; linux-clk@vger.kernel.org > Cc: Sudeep Holla <sudeep.holla@arm.com>; Rajan Vaja <RAJANV@xilinx.com>; > linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; > devicetree@vger.kernel.org > Subject: Re: [PATCH v6 04/11] firmware: xilinx: Add query data API > > > > On 14/05/18 20:16, Jolly Shah wrote: > > HI Sudeep, > > > > [...] > > >> > >> Can you give more insight into this ? How will be this used ? How > >> this aligns with data we get from DT ? I am just trying to understand > >> how is this information split between this API and DT for example. > >> > > > > This API is used to get clock information from firmware and register > > clocks accordingly in driver. In our case, firmware maintains database > > of all clocks available on chip. DT will provide information for off > > chip reference clocks only. This is to avoid duplication of clocks > > data in DT and firmware both as firmware anyways need clock data to > > manage them. > > > > I wanted to understand the difference with example. What kind of information > you get from DT and what you get from firmware ? > > -- > Regards, > Sudeep
Below is an example showing PLL and Leaf clock derivation:
Input ref clocks->Mux->Multiplier/Divider->PLL* Pll1/pll2/pll3/pll4->Mux->Divider->Gate->Leaf clock1
Here Off chip input ref clock information comes from DT. Rest information for Pll/leaf clocks come from firmware using query API. For clock driver, query API is used to get topology, flags, parents etc information per clock.
Thanks, Jolly Shah
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