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Message-ID: <walqtnf2dektptg4uimfmyth5e4l5xod4kavx3bwzmndyekfmd@l5mb2ukuhvza>
Date: Mon, 24 Jul 2023 15:19:38 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Frank Oltmanns <frank@...manns.dev>
Cc: Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
Jernej Skrabec <jernej.skrabec@...il.com>,
Samuel Holland <samuel@...lland.org>,
Andre Przywara <andre.przywara@....com>,
Roman Beranek <me@...y.cz>, linux-clk@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 08/11] clk: sunxi-ng: nkm: Support finding closest rate
On Sun, Jul 23, 2023 at 09:25:10AM +0200, Frank Oltmanns wrote:
> On 2023-07-17 at 16:14:58 +0200, Maxime Ripard <mripard@...nel.org> wrote:
> > [[PGP Signed Part:Undecided]]
> > On Mon, Jul 17, 2023 at 03:34:32PM +0200, Frank Oltmanns wrote:
> >> When finding the best rate for a NKM clock, consider rates that are
> >> higher than the requested rate, if the CCU_FEATURE_CLOSEST_RATE flag is
> >> set by using the helper function ccu_is_better_rate().
> >>
> >> Accommodate ccu_mux_helper_determine_rate to this change.
> >>
> >> Signed-off-by: Frank Oltmanns <frank@...manns.dev>
> >> ---
> >> drivers/clk/sunxi-ng/ccu_mux.c | 2 +-
> >> drivers/clk/sunxi-ng/ccu_nkm.c | 18 ++++++++----------
> >> 2 files changed, 9 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/drivers/clk/sunxi-ng/ccu_mux.c b/drivers/clk/sunxi-ng/ccu_mux.c
> >> index 1d557e323169..3ca695439620 100644
> >> --- a/drivers/clk/sunxi-ng/ccu_mux.c
> >> +++ b/drivers/clk/sunxi-ng/ccu_mux.c
> >> @@ -139,7 +139,7 @@ int ccu_mux_helper_determine_rate(struct ccu_common *common,
> >> goto out;
> >> }
> >>
> >> - if ((req->rate - tmp_rate) < (req->rate - best_rate)) {
> >> + if (ccu_is_better_rate(common, req->rate, tmp_rate, best_rate)) {
> >> best_rate = tmp_rate;
> >> best_parent_rate = parent_rate;
> >> best_parent = parent;
> >> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
> >> index 793160bc2d47..5439b9351cd7 100644
> >> --- a/drivers/clk/sunxi-ng/ccu_nkm.c
> >> +++ b/drivers/clk/sunxi-ng/ccu_nkm.c
> >> @@ -39,6 +39,7 @@ static unsigned long ccu_nkm_optimal_parent_rate(unsigned long rate, unsigned lo
> >> }
> >>
> >> static unsigned long ccu_nkm_find_best_with_parent_adj(struct clk_hw *phw, struct _ccu_nkm *nkm,
> >> + struct ccu_common *common,
> >> unsigned long *parent, unsigned long rate)
> >> {
> >> unsigned long best_rate = 0, best_parent_rate = *parent, tmp_parent = *parent;
> >> @@ -54,10 +55,8 @@ static unsigned long ccu_nkm_find_best_with_parent_adj(struct clk_hw *phw, struc
> >> tmp_parent = clk_hw_round_rate(phw, tmp_parent);
> >>
> >> tmp_rate = tmp_parent * _n * _k / _m;
> >> - if (tmp_rate > rate)
> >> - continue;
> >>
> >> - if ((rate - tmp_rate) < (rate - best_rate)) {
> >> + if (ccu_is_better_rate(common, rate, tmp_rate, best_rate)) {
> >> best_rate = tmp_rate;
> >> best_parent_rate = tmp_parent;
> >> best_n = _n;
> >> @@ -78,7 +77,7 @@ static unsigned long ccu_nkm_find_best_with_parent_adj(struct clk_hw *phw, struc
> >> }
> >>
> >> static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate,
> >> - struct _ccu_nkm *nkm)
> >> + struct _ccu_nkm *nkm, struct ccu_common *common)
> >
> > Same comment than on patch 7, common should be first in those two functions.
> >
>
> Ok, I wasn't sure what your expectation is for existing functions. For
> ccu_find_best_with_parent_adj the order is:
> 1. *phw
> 2. *nkm
> 3. *common
> 4. *parent
> 5. rate
Arguments are generally ordered by putting first what the function will
act upon, and then from generic to specific, and output last.
Which I guess would make the ideal one something like:
*common
*parent_hw
*parent
rate
nkm
> We don't have the parent hw in ccu_nkm_find_best. The order prior to
> this patch is:
> 1. parent
> 2. rate
> 3. *nkm
>
> We need to add *common to that, so I could add it to the beginning as
> per your suggestion:
> 1. *common
> 2. parent
> 3. rate
> 4. *nkm
Those two make sense to me
> I could also pull *nkm to the beginning (similar to the parent_adj
> version):
> 4. *nkm
> 1. *common
> 2. parent
> 3. rate
nkm is an output, it needs to be last.
Maxime
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