Messages in this thread | | | From | Frank Oltmanns <> | Subject | [PATCH v6 00/11] clk: sunxi-ng: Consider alternative parent rates when determining NKM clock rate | Date | Mon, 07 Aug 2023 14:43:33 +0200 |
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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
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@oltmanns.dev>
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