Hi Krzysztof, On 10.06.2020 09:08, Krzysztof Kozlowski wrote: > On Tue, Jun 09, 2020 at 12:42:21PM +0200, Marek Szyprowski wrote: >> Add a simple custom voltage regulator coupler for Exynos5800 SoCs, which >> require coupling between "vdd_arm" and "vdd_int" regulators. This coupler >> ensures that the voltage values don't go below the bootloader-selected >> operation point during the boot process until a the clients sets their >> constraints. It is achieved by assuming minimal voltage value equal to >> the current value if no constraints are set. This also ensures proper >> voltage balancing if any of the client driver is missing. >> >> The balancing code comes from regulator core.c with the > You cut the sentence. Right, looks like a copy/paste issue. I will fix this in v4. >> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> >> --- >> This patch is yet another attempt to fix the regulator coupling on >> Exynos5800/5422 SoCs. Here are links to the previous attempts and >> discussions: >> >> https://lore.kernel.org/linux-samsung-soc/20191008101709.qVNy8eijBi0LynOteWFMnTg4GUwKG599n6OyYoX1Abs@z/ >> https://lore.kernel.org/lkml/20191017102758.8104-1-m.szyprowski@xxxxxxxxxxx/ >> https://lore.kernel.org/linux-pm/cover.1589528491.git.viresh.kumar@xxxxxxxxxx/ >> https://lore.kernel.org/linux-pm/20200528131130.17984-1-m.szyprowski@xxxxxxxxxxx/ >> https://lore.kernel.org/linux-samsung-soc/57cf3a15-5d9b-7636-4c69-60742e8cfae6@xxxxxxxxxxx/ >> https://lore.kernel.org/lkml/20200605063724.9030-1-m.szyprowski@xxxxxxxxxxx/ >> >> The problem is with "vdd_int" regulator coupled with "vdd_arm" on Odroid >> XU3/XU4 boards family. "vdd_arm" is handled by CPUfreq. "vdd_int" is >> handled by devfreq. CPUfreq initialized quite early during boot and it >> starts changing OPPs and "vdd_arm" value. Sometimes CPU activity during >> boot goes down and some low-frequency OPPs are selected, what in turn >> causes lowering "vdd_arm". This happens before devfreq applies its >> requirements on "vdd_int". Regulator balancing code reduces "vdd_arm" >> voltage value, what in turn causes lowering "vdd_int" value to the lowest >> possible value. This is much below the operation point of the wcore bus, >> which still runs at the highest frequency. >> >> The issue was hard to notice because in the most cases the board managed >> to boot properly, even when the regulator was set to lowest value allowed >> by the regulator constraints. However, it caused some random issues, >> which can be observed as "Unhandled prefetch abort" or low USB stability. >> >> Handling this case in the generic code has been rejected, so the only way >> to ensure the desired behavior on Exynos5800-based SoCs is to make a >> custom regulator coupler driver. I've tried hard to extract some common >> code to simplify the exynos-regulator-coupler driver as much as possible, >> but the difference between it and the generic code is so deep that this >> approach failed, so indead I simply copied and modified the balancing >> code. >> >> Best regards >> Marek Szyprowski >> --- >> arch/arm/mach-exynos/Kconfig | 1 + >> drivers/soc/samsung/Kconfig | 3 + >> drivers/soc/samsung/Makefile | 1 + >> .../soc/samsung/exynos-regulator-coupler.c | 221 ++++++++++++++++++ >> 4 files changed, 226 insertions(+) >> create mode 100644 drivers/soc/samsung/exynos-regulator-coupler.c >> >> diff --git a/arch/arm/mach-exynos/Kconfig b/arch/arm/mach-exynos/Kconfig >> index 76838255b5fa..f185cd3d4c62 100644 >> --- a/arch/arm/mach-exynos/Kconfig >> +++ b/arch/arm/mach-exynos/Kconfig >> @@ -118,6 +118,7 @@ config SOC_EXYNOS5800 >> bool "Samsung EXYNOS5800" >> default y >> depends on SOC_EXYNOS5420 >> + select EXYNOS_REGULATOR_COUPLER >> >> config EXYNOS_MCPM >> bool >> diff --git a/drivers/soc/samsung/Kconfig b/drivers/soc/samsung/Kconfig >> index 19c4d3f1437b..5d7819b52eed 100644 >> --- a/drivers/soc/samsung/Kconfig >> +++ b/drivers/soc/samsung/Kconfig >> @@ -43,4 +43,7 @@ config EXYNOS_PM_DOMAINS >> bool "Exynos PM domains" if COMPILE_TEST >> depends on PM_GENERIC_DOMAINS || COMPILE_TEST >> >> +config EXYNOS_REGULATOR_COUPLER >> + bool "Exynos SoC Regulator Coupler" if COMPILE_TEST >> + depends on ARCH_EXYNOS || COMPILE_TEST >> endif >> diff --git a/drivers/soc/samsung/Makefile b/drivers/soc/samsung/Makefile >> index 31db65cb7aa3..93285faec416 100644 >> --- a/drivers/soc/samsung/Makefile >> +++ b/drivers/soc/samsung/Makefile >> @@ -10,3 +10,4 @@ obj-$(CONFIG_EXYNOS_PMU_ARM_DRIVERS) += exynos3250-pmu.o exynos4-pmu.o \ >> exynos5250-pmu.o exynos5420-pmu.o >> obj-$(CONFIG_EXYNOS_PMU_ARM64_DRIVERS) += exynos-pm.o exynos5433-pmu.o >> obj-$(CONFIG_EXYNOS_PM_DOMAINS) += pm_domains.o >> +obj-$(CONFIG_EXYNOS_REGULATOR_COUPLER) += exynos-regulator-coupler.o >> diff --git a/drivers/soc/samsung/exynos-regulator-coupler.c b/drivers/soc/samsung/exynos-regulator-coupler.c >> new file mode 100644 >> index 000000000000..3cafc1738eb6 >> --- /dev/null >> +++ b/drivers/soc/samsung/exynos-regulator-coupler.c >> @@ -0,0 +1,221 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* >> + * Copyright (c) 2020 Samsung Electronics Co., Ltd. >> + * http://www.samsung.com/ >> + * Author: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> >> + * >> + * Simplified generic volatage coupler from regulator core.c >> + * The main difference is that it keeps current regulator voltage >> + * if consumers didn't apply their contraints yet. >> + */ >> + >> +#include <linux/init.h> >> +#include <linux/kernel.h> >> +#include <linux/of.h> >> +#include <linux/regulator/coupler.h> >> +#include <linux/regulator/driver.h> >> +#include <linux/regulator/machine.h> >> + >> +static int regulator_get_optimal_voltage(struct regulator_dev *rdev, >> + int *current_uV, >> + int *min_uV, int *max_uV, >> + suspend_state_t state) >> +{ >> + struct coupling_desc *c_desc = &rdev->coupling_desc; >> + struct regulator_dev **c_rdevs = c_desc->coupled_rdevs; >> + struct regulation_constraints *constraints = rdev->constraints; >> + int desired_min_uV = 0, desired_max_uV = INT_MAX; >> + int max_current_uV = 0, min_current_uV = INT_MAX; >> + int highest_min_uV = 0, target_uV, possible_uV; >> + int i, ret, max_spread, n_coupled = c_desc->n_coupled; >> + bool done; >> + >> + *current_uV = -1; >> + >> + /* Find highest min desired voltage */ >> + for (i = 0; i < n_coupled; i++) { >> + int tmp_min = 0; >> + int tmp_max = INT_MAX; >> + >> + lockdep_assert_held_once(&c_rdevs[i]->mutex.base); >> + >> + ret = regulator_check_consumers(c_rdevs[i], >> + &tmp_min, >> + &tmp_max, state); >> + if (ret < 0) >> + return ret; >> + >> + if (tmp_min == 0) { >> + ret = regulator_get_voltage_rdev(c_rdevs[i]); >> + if (ret < 0) >> + return ret; >> + tmp_min = ret; >> + } >> + >> + /* apply constraints */ >> + ret = regulator_check_voltage(c_rdevs[i], &tmp_min, &tmp_max); >> + if (ret < 0) >> + return ret; >> + >> + highest_min_uV = max(highest_min_uV, tmp_min); >> + >> + if (i == 0) { >> + desired_min_uV = tmp_min; >> + desired_max_uV = tmp_max; >> + } >> + } >> + >> + max_spread = constraints->max_spread[0]; >> + >> + /* >> + * Let target_uV be equal to the desired one if possible. >> + * If not, set it to minimum voltage, allowed by other coupled >> + * regulators. >> + */ >> + target_uV = max(desired_min_uV, highest_min_uV - max_spread); >> + >> + /* >> + * Find min and max voltages, which currently aren't violating >> + * max_spread. >> + */ >> + for (i = 1; i < n_coupled; i++) { >> + int tmp_act; >> + >> + tmp_act = regulator_get_voltage_rdev(c_rdevs[i]); >> + if (tmp_act < 0) >> + return tmp_act; >> + >> + min_current_uV = min(tmp_act, min_current_uV); >> + max_current_uV = max(tmp_act, max_current_uV); >> + } >> + >> + /* >> + * Correct target voltage, so as it currently isn't >> + * violating max_spread >> + */ >> + possible_uV = max(target_uV, max_current_uV - max_spread); >> + possible_uV = min(possible_uV, min_current_uV + max_spread); >> + >> + if (possible_uV > desired_max_uV) >> + return -EINVAL; >> + >> + done = (possible_uV == target_uV); >> + desired_min_uV = possible_uV; >> + >> + /* Set current_uV if wasn't done earlier in the code and if necessary */ >> + if (*current_uV == -1) { >> + ret = regulator_get_voltage_rdev(rdev); >> + if (ret < 0) >> + return ret; >> + *current_uV = ret; >> + } >> + >> + *min_uV = desired_min_uV; >> + *max_uV = desired_max_uV; >> + >> + return done; >> +} >> + >> +static int exynos_coupler_balance_voltage(struct regulator_coupler *coupler, >> + struct regulator_dev *rdev, >> + suspend_state_t state) >> +{ >> + struct regulator_dev **c_rdevs; >> + struct regulator_dev *best_rdev; >> + struct coupling_desc *c_desc = &rdev->coupling_desc; >> + int i, ret, n_coupled, best_min_uV, best_max_uV, best_c_rdev; >> + unsigned int delta, best_delta; >> + unsigned long c_rdev_done = 0; >> + bool best_c_rdev_done; >> + >> + c_rdevs = c_desc->coupled_rdevs; >> + n_coupled = c_desc->n_coupled; >> + >> + /* >> + * Find the best possible voltage change on each loop. Leave the loop >> + * if there isn't any possible change. >> + */ >> + do { >> + best_c_rdev_done = false; >> + best_delta = 0; >> + best_min_uV = 0; >> + best_max_uV = 0; >> + best_c_rdev = 0; >> + best_rdev = NULL; >> + >> + /* >> + * Find highest difference between optimal voltage >> + * and current voltage. >> + */ >> + for (i = 0; i < n_coupled; i++) { >> + /* >> + * optimal_uV is the best voltage that can be set for >> + * i-th regulator at the moment without violating >> + * max_spread constraint in order to balance >> + * the coupled voltages. >> + */ >> + int optimal_uV = 0, optimal_max_uV = 0, current_uV = 0; >> + >> + if (test_bit(i, &c_rdev_done)) > Add a sanity check at beginning that you have enough of bits for this... > or use bitmap. Frankly, even regulator core uses this simple approach. I doubt that there will be more than 32 coupled regulators ever... Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
