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Message-ID: <CAGb2v66dU2Ao9hBiwgu32i7_svqMT+Pz=BVnN0ZvmLhFm+jy6A@mail.gmail.com>
Date: Thu, 10 Aug 2023 00:44:53 +0800
From: Chen-Yu Tsai <wens@...e.org>
To: Frank Oltmanns <frank@...manns.dev>
Cc: Maxime Ripard <mripard@...nel.org>,
Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.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 v6 00/11] clk: sunxi-ng: Consider alternative parent rates
when determining NKM clock rate
On Mon, Aug 7, 2023 at 8:44 PM Frank Oltmanns <frank@...manns.dev> wrote:
>
> This patchset enables NKM clocks to consider alternative parent rates
> and utilize this new feature to adjust the pll-video0 clock on Allwinner
> A64.
>
> Furthermore, with this patchset pll-video0 considers rates that are
> higher than the requested rate when finding the closest rate. In
> consequence, higher rates are also considered by pll-video0's
> descandents. In total, after applying this patchset, finding the closest
> rate is supported by:
> - ccu_nm
> - ccu_nkm
> - ccu_mux
> - ccu_div
>
> This allows us to achieve an optimal rate for driving the board's panel.
>
> To provide some context, the clock structure involved in this process is
> as follows:
> clock clock type
> --------------------------------------
> pll-video0 ccu_nm
> pll-mipi ccu_nkm
> tcon0 ccu_mux
> tcon-data-clock sun4i_dclk
>
> The divider between tcon0 and tcon-data-clock is fixed at 4. Therefore,
> in order to achieve a rate that closely matches the desired rate of the
> panel, pll-mipi needs to operate at a specific rate.
>
> Tests
> =====
> So far, this has been successfully tested on the A64-based Pinephone
> using three different panel rates:
>
> 1. A panel rate that can be matched exactly by pll-video0.
> 2. A panel rate that requires pll-video0 to undershoot to get the
> closest rate.
> 3. A panel rate that requires pll-video0 to overshoot to get the
> closest rate.
>
> Test records:
>
> Re 1:
> -----
> Panel requests tcon-data-clock of 103500000 Hz, i.e., pll-mipi needs to
> run at 414000000 Hz. This results in the following clock rates:
> clock rate
> -------------------------------------
> pll-video0 207000000
> hdmi-phy-clk 51750000
> hdmi 207000000
> tcon1 207000000
> pll-mipi 414000000
> tcon0 414000000
> tcon-data-clock 103500000
>
> The results of the find_best calls:
> ccu_nkm_find_best_with_parent_adj: rate=414000000, best_rate=414000000, best_parent_rate=207000000, n=1, k=2, m=1
> ccu_nkm_find_best_with_parent_adj: rate=414000000, best_rate=414000000, best_parent_rate=207000000, n=1, k=2, m=1
> ccu_nkm_find_best_with_parent_adj: rate=414000000, best_rate=414000000, best_parent_rate=207000000, n=1, k=2, m=1
> ccu_nkm_find_best_with_parent_adj: rate=414000000, best_rate=414000000, best_parent_rate=207000000, n=1, k=2, m=1
> ccu_nkm_find_best: rate=414000000, best_rate=414000000, parent_rate=207000000, n=1, k=2, m=1
>
> Re 2:
> -----
> Panel requests tcon-data-clock of 103650000 Hz, i.e., pll-mipi needs to
> run at 414600000 Hz. This results in the following clock rates:
> clock rate
> -------------------------------------
> pll-video0 282666666
> hdmi-phy-clk 70666666
> hdmi 282666666
> tcon1 282666666
> pll-mipi 414577776
> tcon0 414577776
> tcon-data-clock 103644444
>
> The results of the find_best calls:
> ccu_nkm_find_best_with_parent_adj: rate=414600000, best_rate=414577776, best_parent_rate=282666666, n=11, k=2, m=15
> ccu_nkm_find_best_with_parent_adj: rate=414600000, best_rate=414577776, best_parent_rate=282666666, n=11, k=2, m=15
> ccu_nkm_find_best_with_parent_adj: rate=414577776, best_rate=414577776, best_parent_rate=282666666, n=11, k=2, m=15
> ccu_nkm_find_best_with_parent_adj: rate=414577776, best_rate=414577776, best_parent_rate=282666666, n=11, k=2, m=15
> ccu_nkm_find_best: rate=414577776, best_rate=414577776, parent_rate=282666666, n=11, k=2, m=15
>
> Re 3:
> -----
> Panel requests tcon-data-clock of 112266000 Hz, i.e., pll-mipi needs to
> run at 449064000 Hz. This results in the following clock rates:
> clock rate
> -------------------------------------
> pll-video0 207272727
> hdmi-phy-clk 51818181
> hdmi 207272727
> tcon1 207272727
> pll-mipi 449090908
> tcon0 449090908
> tcon-data-clock 112272727
>
> The results of the find_best calls:
> ccu_nkm_find_best_with_parent_adj: rate=449064000, best_rate=449090908, best_parent_rate=207272727, n=13, k=2, m=12
> ccu_nkm_find_best_with_parent_adj: rate=449064000, best_rate=449090908, best_parent_rate=207272727, n=13, k=2, m=12
> ccu_nkm_find_best_with_parent_adj: rate=449090908, best_rate=449090908, best_parent_rate=207272727, n=13, k=2, m=12
> ccu_nkm_find_best_with_parent_adj: rate=449090908, best_rate=449090908, best_parent_rate=207272727, n=13, k=2, m=12
> ccu_nkm_find_best: rate=449090908, best_rate=449090908, parent_rate=207272727, n=13, k=2, m=12
>
> Changelog:
> ----------
> Changes in v6:
> - Removed unnecessary #include from ccu_nkm.c
> - Link to v5: https://lore.kernel.org/r/20230806-pll-mipi_set_rate_parent-v5-0-db4f5ca33fc3@oltmanns.dev
>
> Changes in v5:
> - Remove the dedicated function for calculating the optimal parent rate
> for nkm clocks that was introduced in v2 and again in v4. Instead use
> a simple calculation and require the parent clock to select the
> closest rate to achieve optimal results.
> - Change the order of parameters of nkm_best_rate and
> nkm_best_rate_with_parent_adj as requested my Maxime Ripard.
> - Prefer to not reset the rate of the nkm clock's parent if the ideal
> rate can be reached using the parent's current rate, copying the
> behavior of ccu_mp.
> - Link to v4: https://lore.kernel.org/r/20230717-pll-mipi_set_rate_parent-v4-0-04acf1d39765@oltmanns.dev
>
> Changes in v4:
> - Re-introduce a dedicated function for calculating the optimal parent
> rate for nkm clocks that was introduced in v2 and removed in v3. It
> turned out that not having this functionality introduces a bug when
> the parent does not support finding the closest rate:
> https://lore.kernel.org/all/87pm4xg2ub.fsf@oltmanns.dev/
> - Incorporate review remarks:
> - Correcting the parameter name for ccu_nkm_round_rate()'s parent HW
> is now in a separate patch.
> - Use correct parameter order in ccu_nkm_find_best_with_parent_adj.
> - Add ccu_is_better_rate() and use it for determining the best rate
> for nm and nkm, as well as ccu_mux_helper_determine_rate.
> - Consistently introduce new macros for clock variants that support
> finding the closest rate instead of updating existing macros.
> - Use wrapper function for determining a ccu_mux's rate in order to
> support finding the closest rate.
> - Link to v3: https://lore.kernel.org/r/20230702-pll-mipi_set_rate_parent-v3-0-46dcb8aa9cbc@oltmanns.dev
>
> Changes in v3:
> - Use dedicated function for finding the best rate in cases where an
> nkm clock supports setting its parent's rate, streamlining it with
> the structure that is used in other sunxi-ng ccus such as ccu_mp
> (PATCH 1).
> - Therefore, remove the now obsolete comments that were introduced in
> v2 (PATCH 1).
> - Remove the dedicated function for calculating the optimal parent rate
> for nkm clocks that was introduced in v2. Instead use a simple
> calculation and require the parent clock to select the closest rate to
> achieve optimal results (PATCH 1).
> - Therefore, add support to set the closest rate for nm clocks (because
> pll-mipi's parent pll-video0 is an nm clock) and all clock types that
> are descendants of a64's pll-video0, i.e., nkm, mux, and div (PATCH 3
> et. seq.).
> - Link to v2: https://lore.kernel.org/all/20230611090143.132257-1-frank@oltmanns.dev/
>
> Changes in V2:
> - Move optimal parent rate calculation to dedicated function
> - Choose a parent rate that does not to overshoot requested rate
> - Add comments to ccu_nkm_find_best
> - Make sure that best_parent_rate stays at original parent rate in the unlikely
> case that all combinations overshoot.
>
> Link to V1:
> https://lore.kernel.org/lkml/20230605190745.366882-1-frank@oltmanns.dev/
>
> ---
> Frank Oltmanns (11):
> clk: sunxi-ng: nkm: Use correct parameter name for parent HW
> clk: sunxi-ng: nkm: consider alternative parent rates when determining rate
> clk: sunxi-ng: a64: allow pll-mipi to set parent's rate
> clk: sunxi-ng: Add feature to find closest rate
> clk: sunxi-ng: Add helper function to find closest rate
> clk: sunxi-ng: nm: Support finding closest rate
> clk: sunxi-ng: nkm: Support finding closest rate
> clk: sunxi-ng: mux: Support finding closest rate
> clk: sunxi-ng: div: Support finding closest rate
> clk: sunxi-ng: a64: select closest rate for pll-video0
> clk: sunxi-ng: nkm: Prefer current parent rate
Whole series applied. There were some conflicts on patch 10 I had to
fix up. I also took the liberty of realigning some of the lines.
Please check if things are correct:
https://git.kernel.org/pub/scm/linux/kernel/git/sunxi/linux.git/commit/?h=sunxi/clk-for-6.6&id=bf8eb12f52c49e10ca1d86564bfa096e09c51c38
ChenYu
> drivers/clk/sunxi-ng/ccu-sun50i-a64.c | 36 ++++++++++-------------
> drivers/clk/sunxi-ng/ccu_common.c | 12 ++++++++
> drivers/clk/sunxi-ng/ccu_common.h | 6 ++++
> drivers/clk/sunxi-ng/ccu_div.h | 30 +++++++++++++++++++
> drivers/clk/sunxi-ng/ccu_mux.c | 15 ++++++++--
> drivers/clk/sunxi-ng/ccu_mux.h | 38 +++++++++++++++++-------
> drivers/clk/sunxi-ng/ccu_nkm.c | 55 ++++++++++++++++++++++++++++++-----
> drivers/clk/sunxi-ng/ccu_nm.c | 13 ++++-----
> drivers/clk/sunxi-ng/ccu_nm.h | 48 ++++++++++++++++++++++++++++--
> 9 files changed, 202 insertions(+), 51 deletions(-)
> ---
> base-commit: 6995e2de6891c724bfeb2db33d7b87775f913ad1
> change-id: 20230626-pll-mipi_set_rate_parent-3363fc0d6e6f
>
> Best regards,
> --
> Frank Oltmanns <frank@...manns.dev>
>
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