From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prashant Gaikwad Date: Thu, 12 Jul 2012 04:26:11 +0000 Subject: Re: Device tree binding for DVFS table Message-Id: <4FFE4F13.2040402@nvidia.com> List-Id: References: <4FFD77FE.8050206@nvidia.com> <4FFD87BD.2030206@gmail.com> <20120711144449.GA23654@sirena.org.uk> <20120711200402.GC2772@gmail.com> In-Reply-To: <20120711200402.GC2772@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org On Thursday 12 July 2012 01:34 AM, Mike Turquette wrote: > On 20120711-15:44, Mark Brown wrote: >> On Wed, Jul 11, 2012 at 09:03:41AM -0500, Rob Herring wrote: >> >>> I'd expect a single property with freq/volt pairs or 2 properties for >>> freq and voltage where there is a 1:1 relationship (freq N uses voltage N). >> I strongly agree - the current proposal is very hard to read due to the >> separation between the voltage and frequency values. Some devices do >> also need to scale multiple rails together, especially when this gets >> used for I/O devices. >> >> I'd also expect to see a range of voltages for each frequency rather >> than a specific voltage; usually things are at least characterised with >> a specified tolerance. > Not only should we support multiple voltage rails but also multiple > clocks. For some devices a DVFS transition is composed of scaling > multiple clock rates together. So some sort of clock identifier > (phandle?) is needed as well. (forgive my ignorance on the phandle > part, as I am a DT noob) How about adding phandle of clock consumer node to frequency table? > Regards, > Mike From mboxrd@z Thu Jan 1 00:00:00 1970 From: pgaikwad@nvidia.com (Prashant Gaikwad) Date: Thu, 12 Jul 2012 09:44:11 +0530 Subject: Device tree binding for DVFS table In-Reply-To: <20120711200402.GC2772@gmail.com> References: <4FFD77FE.8050206@nvidia.com> <4FFD87BD.2030206@gmail.com> <20120711144449.GA23654@sirena.org.uk> <20120711200402.GC2772@gmail.com> Message-ID: <4FFE4F13.2040402@nvidia.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thursday 12 July 2012 01:34 AM, Mike Turquette wrote: > On 20120711-15:44, Mark Brown wrote: >> On Wed, Jul 11, 2012 at 09:03:41AM -0500, Rob Herring wrote: >> >>> I'd expect a single property with freq/volt pairs or 2 properties for >>> freq and voltage where there is a 1:1 relationship (freq N uses voltage N). >> I strongly agree - the current proposal is very hard to read due to the >> separation between the voltage and frequency values. Some devices do >> also need to scale multiple rails together, especially when this gets >> used for I/O devices. >> >> I'd also expect to see a range of voltages for each frequency rather >> than a specific voltage; usually things are at least characterised with >> a specified tolerance. > Not only should we support multiple voltage rails but also multiple > clocks. For some devices a DVFS transition is composed of scaling > multiple clock rates together. So some sort of clock identifier > (phandle?) is needed as well. (forgive my ignorance on the phandle > part, as I am a DT noob) How about adding phandle of clock consumer node to frequency table? > Regards, > Mike