From: Stephen Boyd <firstname.lastname@example.org> To: Janek Kotas <email@example.com> Cc: "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com> Subject: Re: [PATCH 2/2] clk: Add Fixed MMIO clock driver Date: Fri, 30 Nov 2018 00:58:30 -0800 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <76BDCB72-CC05-41D1-93A0-6D71CBD97651@global.cadence.com> Quoting Janek Kotas (2018-11-30 00:52:16) > > We have a single register in a fixed location which contains > the frequency of the main system clock. > This allows us to use the same image in emulation, FPGA > and simulation without any changes. > We usually don’t use a full bootloader, just a simple wrapper, > which initializes the necessary stuff and jumps to the kernel. > > > So the hardware team has decided to throw a frequency register in there? > Alright! Does that fixed rate clk generate its fixed rate from some > other clk? I’m curious if this fixed rate clk has a parent source. > > > It depends, in simulation and emulation we can just generate > a clock source with a given frequency. > On FPGA it’s usually an external oscillator, sometimes a fixed PLL. > The driver is not intended to be used in full, complex SoCs. Ok, sounds like it isn't worth modeling this then. > > > It would also be good to make sure that any clks registered from this > driver can't be populated from regions of memory like DDR. Can you > confirm? I think it will fail, but it would be worth checking > Please try this. > Yes I'd prefer a platform driver unless there's some reason it can't be > done. We may need to have both in case this needs to be populated very > early, but if that isn’t the case then just a platform driver for now. > > > I played with it a bit, and it and it looks like I need both. > We use this clock source with some of our components, > and for some of them the platform driver was initialized too late. > Ok. So do both then.
next prev parent reply other threads:[~2018-11-30 8:58 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-11-14 15:24 Janek Kotas 2018-11-14 22:19 ` Stephen Boyd 2018-11-15 8:27 ` Janek Kotas 2018-11-29 22:29 ` Stephen Boyd [not found] ` <76BDCB72-CC05-41D1-93A0-6D71CBD97651@global.cadence.com> 2018-11-30 8:58 ` Stephen Boyd [this message] [not found] ` <63A29785-D1AC-4B7C-952E-3A2E5799A21D@global.cadence.com> 2018-11-30 18:56 ` Stephen Boyd
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