lkml.org 
[lkml]   [2019]   [Nov]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH v5 1/3] clk: qcom: Allow constant ratio freq tables for rcg
Date
Quoting Jeffrey Hugo (2019-11-07 14:12:09)
> On Thu, Nov 7, 2019 at 2:43 PM Stephen Boyd <sboyd@kernel.org> wrote:
> >
> > Quoting Jeffrey Hugo (2019-10-31 11:57:15)
> > > Some RCGs (the gfx_3d_src_clk in msm8998 for example) are basically just
> > > some constant ratio from the input across the entire frequency range. It
> > > would be great if we could specify the frequency table as a single entry
> > > constant ratio instead of a long list, ie:
> > >
> > > { .src = P_GPUPLL0_OUT_EVEN, .pre_div = 3 },
> > > { }
> > >
> > > So, lets support that.
> > >
> > > We need to fix a corner case in qcom_find_freq() where if the freq table
> > > is non-null, but has no frequencies, we end up returning an "entry" before
> > > the table array, which is bad. Then, we need ignore the freq from the
> > > table, and instead base everything on the requested freq.
> > >
> > > Suggested-by: Stephen Boyd <sboyd@kernel.org>
> > > Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
> > > ---
> >
> > Applied to clk-next and fixed the space thing. I guess ceil/floor
> > rounding isn't a problem?
> >
>
> Thanks for fixing the nit.
>
> Hmm. Looking back at it, floor is only used with the rcg_floor_ops.
> Right now, you can't use a constant ratio table with rcg_floor_ops -
> looks like you'd probably hit a null pointer dereference. I'm having
> trouble seeing how the floor operation would work with this constant
> ratio idea in a way that would be different than the normal rcg_ops.
> I think I would say that either you have a good reason for using the
> constant ratio table, in which case you should be using the normal
> rcg_ops, or you have a good reason for using floor which is then
> incompatible with a constant ratio table. If you think that the
> constant ratio table concept should be applied to floor ops, can you
> please detail what you expect the behavior to be?

I don't think floor ops make sense. I just wanted to make sure that the
floor and ceiling stuff in here isn't going to cause problems. Looking
again after reading your response I think we're going to be fine.

\
 
 \ /
  Last update: 2019-11-08 07:45    [W:0.048 / U:4.540 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site