On Fri, 19 Apr 2019 11:56:25 +0530 Jagan Teki <ja...@amarulasolutions.com> wrote:
> On Fri, Apr 5, 2019 at 2:20 AM Lukasz Majewski <lu...@denx.de> wrote: > > > > Hi Jagan, > > > > > On Thu, Apr 4, 2019 at 3:31 PM Lukasz Majewski <lu...@denx.de> > > > wrote: > > > > > > > > On Thu, 4 Apr 2019 14:56:36 +0530 > > > > Jagan Teki <ja...@amarulasolutions.com> wrote: > > > > > > > > > On Thu, Apr 4, 2019 at 2:31 PM Lukasz Majewski <lu...@denx.de> > > > > > wrote: > > > > > > > > > > > > On Tue, 2 Apr 2019 16:58:33 +0530 > > > > > > Jagan Teki <ja...@amarulasolutions.com> wrote: > > > > > > > > > > > > > This is revised version of previous i.MX6 clock management > > > > > > > [1]. > > > > > > > > > > > > > > The main difference between previous version is > > > > > > > - Group the i.MX6 ccm clocks into gates and tree instead > > > > > > > of handling the clocks in simple way using case statement. > > > > > > > - use gate clocks for enable/disable management. > > > > > > > - use tree clocks for get/set rate or parent traverse > > > > > > > management. > > > > > > > - parent clock handling via clock type. > > > > > > > - traverse the parent clock using recursive functionlaity. > > > > > > > > > > > > > > The main motive behind this tree framework is to make the > > > > > > > clock tree management simple and useful for U-Boot > > > > > > > requirements instead of garbing Linux clock management > > > > > > > code. > > > > > > > > > > > > > > We are trying to manage the Allwinner clocks with similar > > > > > > > kind, so having this would really help i.MX6 as well. > > > > > > > > > > > > > > Added simple names for clock macros, but will update it in > > > > > > > future version. > > > > > > > > > > > > > > I have skipped ENET clocks from previous series, will add > > > > > > > it in future patches. > > > > > > > > > > > > > > Changes for v2: > > > > > > > - changed framework patches. > > > > > > > - add support for imx6qdl and imx6ul boards > > > > > > > - add clock gates, tree. > > > > > > > > > > > > > > [1] https://patchwork.ozlabs.org/cover/950964/ > > > > > > > > > > > > > > Any inputs? > > > > > > > > > > > > Hmm.... It looks like we are doing some development in > > > > > > parallel. > > > > > > > > > > > > Please look into following commit [1]: > > > > > > https://patchwork.ozlabs.org/patch/1034051/ > > > > > > > > > > > > It ports from Linux 5.0 the CCF framework for iMX6Q, which > > > > > > IMHO in the long term is a better approach. > > > > > > The code is kept simple and resembles the code from Barebox. > > > > > > > > > > > > Please correct me if I'm wrong, but the code from your work > > > > > > is not modeling muxes, gates and other components from > > > > > > Linux CCF. > > > > > > > > > > The U-Boot implementation of CLK would require as minimal and > > > > > simple as possible due to requirement of U-Boot itself. Hope > > > > > you agree this point? > > > > > > > > Now i.MX6 is using clock.c CLK implementation. If we decide to > > > > replace it - we shall do it in a way, which would allow us to > > > > follow Linux kernel. (the barebox implementation is a stripped > > > > CCF from Linux, the same is in patch [1]). > > > > > > > > > if yes having CCF stack code to handle all clock with > > > > > respective separate drivers management is may not require as > > > > > of now, IMHO. > > > > > > > > I do have a gut feeling, that we will end up with the need to > > > > have the CCF framework ported anyway. As for example imx7/8 can > > > > re-use muxes, gates code. > > > > > > As per my experience the main the over-ahead to handle clocks in > > > U-Boot if we go with separate clock drivers is for Video and > > > Ethernet peripherals. these are key IP's which use more clocks > > > from U-Boot point-of-view, others can be handle pretty > > > straight-forward unless if they don't have too much tree chain. > > > > > > On this series, the tree management is already supported ENET in > > > i.MX6, and Allwinner platforms. > > > > > > As of now, I'm thinking I can handle reset of the clocks with > > > similar way. > > > > But this code also supports ENET and ESDHCI clocks on i.MX6Q (as > > supporting those was the motivator for this work). > > > > One important thing to be aware of - the problem with SPL's > > footprint. The implementation with clock.c is small and simple, but > > doesn't scale well. > > > > > > > > > > > > > However, those are only my "feelings" after a glimpse look - I > > > > will look into your code more thoroughly and provide feedback. > > > > > > Please have a look, if possible check even the code size by adding > > > USDHC clocks. > > > > Yes, code size (especially in SPL) is an _important_ factor here. > > > > > > > > > > > > > > > > > > > This series is using recursive calls for handling parenting > > > > > stuff to handle get or set rates, which is fine for handling > > > > > clock tree management as far as U-Boot point-of-view. We have > > > > > faced similar situation as I explained in commit message > > > > > about Allwinner clocks [2] and we ended up going this way. > > > > > > > > I'm not Allwinner expert - but if I may ask - how far away is > > > > this implementation from mainline Linux kernel? > > > > > > > > How difficult is it to port the new code (or update it)? > > > > > > Allwinner clocks also has similar gates, muxs, and with other > > > platform stuff which has too much scope in Linux to use CCM. > > > > For example the barebox managed to get subset of Linux CCF ported, > > without loosing the CCF similarity. > > > > > > Important factors/requirements for the i.MX clock code: > > > > 1. Easy maintenance in long-term > > > > 2. Reusing the code in SPL (with a very important factor of > > _code_size_). > > > > 3. Reuse the code for other i.MX SoCs (imx7, imx8) > > > > 4. Effort needed to use DM with this code > > I understand your points, I was managed this series based on these > requirements as well. Ok. Could you share the delta of footprint size (u-boot.img/SPL) with and without your patch (on imx6q) ? In my case the CCF caused increase of u-boot.img proper (as it was not yet adapted to SPL): 415KiB -> 421KiB = 6KiB increase of size (< 2%). (This can be further reduced by using OF_PLATDATA). This CCF code hasn't been ported to SPL (yet) > We even consider the foot-print, atleast for > recursive calls of handling parenting scale well. With CCF porting v3 I'm going to provide some caching, so the descending would be done at most once. > May be we can > consider to design based on this as per U-Boot. > Please look into point 1. Having code ported from Linux is IMHO better in the long term. > Let me come-back with another series or do you have any inputs or > questions, please post it. I will post CCF port for imx6q v3 in a few days. > > Jagan. Best regards, Lukasz Majewski -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lu...@denx.de
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