From patchwork Mon Jul 17 13:34:24 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frank Oltmanns X-Patchwork-Id: 13316473 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mout-p-202.mailbox.org ([2001:67c:2050:0:465::202]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qLONF-0048RB-0g for linux-arm-kernel@lists.infradead.org; Mon, 17 Jul 2023 13:34:59 +0000 From: Frank Oltmanns Subject: [PATCH v4 00/11] clk: sunxi-ng: Consider alternative parent rates when determining NKM clock rate Date: Mon, 17 Jul 2023 15:34:24 +0200 Message-Id: <20230717-pll-mipi_set_rate_parent-v4-0-04acf1d39765@oltmanns.dev> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+lwn-linux-arm-kernel=archive.lwn.net@lists.infradead.org List-Archive: To: Maxime Ripard , Michael Turquette , Stephen Boyd , Chen-Yu Tsai , Jernej Skrabec , Samuel Holland , Andre Przywara , Roman Beranek Cc: linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org, Frank Oltmanns This patchset enables NKM clocks to consider alternative parent rates and utilize this new feature to adjust the pll-video0 clock on Allwinner A64 (PATCH 2 and 3). 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 (PATCH 4 et. seq.). 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 Here, we first ask pll-video0 for a rate that it can't provide exactly: - rate=414600000: We ask the parent for rate * m / (n * k) = 282681818, it returns 282666666. Here the parent undershoots. Later we ask pll-video0 for exactly that rate again: - rate=414577776: We ask the parent for DIV_ROUND_UP(rate * m, n * k) = 282666666, which it then returns. 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 Here, we first ask the pll-video0 for a rate that it can't provide exactly: - rate=449064000: We ask the parent for DIV_ROUND_UP(rate * m, n * k) = 207260308, it returns 207272727. Here the parent overshoots. Later we ask pll-video0 for exactly that rate again: - rate=449090908: We ask the parent for DIV_ROUND_UP(rate * m, n * k) = 207272727, which it then returns. Changelog: ---------- 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: nkm: Improve determine rate when setting parent 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 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 | 76 +++++++++++++++++++++++++++++++---- drivers/clk/sunxi-ng/ccu_nm.c | 11 ++--- drivers/clk/sunxi-ng/ccu_nm.h | 48 ++++++++++++++++++++-- 9 files changed, 222 insertions(+), 50 deletions(-) --- base-commit: 6995e2de6891c724bfeb2db33d7b87775f913ad1 change-id: 20230626-pll-mipi_set_rate_parent-3363fc0d6e6f Best regards,