@@ -43,6 +43,11 @@ config MTK_PMIC_WRAP
on different MediaTek SoCs. The PMIC wrapper is a proprietary
hardware to connect the PMIC.
+config MTK_REGULATOR_COUPLER
+ bool "MediaTek SoC Regulator Coupler" if COMPILE_TEST
+ default ARCH_MEDIATEK
+ depends on REGULATOR
+
config MTK_SCPSYS
bool "MediaTek SCPSYS Support"
default ARCH_MEDIATEK
@@ -3,6 +3,7 @@ obj-$(CONFIG_MTK_CMDQ) += mtk-cmdq-helper.o
obj-$(CONFIG_MTK_DEVAPC) += mtk-devapc.o
obj-$(CONFIG_MTK_INFRACFG) += mtk-infracfg.o
obj-$(CONFIG_MTK_PMIC_WRAP) += mtk-pmic-wrap.o
+obj-$(CONFIG_MTK_REGULATOR_COUPLER) += mtk-regulator-coupler.o
obj-$(CONFIG_MTK_SCPSYS) += mtk-scpsys.o
obj-$(CONFIG_MTK_SCPSYS_PM_DOMAINS) += mtk-pm-domains.o
obj-$(CONFIG_MTK_MMSYS) += mtk-mmsys.o
new file mode 100644
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Voltage regulators coupler for MediaTek SoCs
+ *
+ * Copyright (C) 2022 Collabora, Ltd.
+ * Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#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>
+#include <linux/suspend.h>
+
+#define to_mediatek_coupler(x) container_of(x, struct mediatek_regulator_coupler, coupler)
+
+struct mediatek_regulator_coupler {
+ struct regulator_coupler coupler;
+ struct regulator_dev *vsram_rdev;
+};
+
+/*
+ * We currently support only couples of not more than two vregs and
+ * modify the vsram voltage only when changing voltage of vgpu.
+ *
+ * This function is limited to the GPU<->SRAM voltages relationships.
+ */
+static int mediatek_regulator_balance_voltage(struct regulator_coupler *coupler,
+ struct regulator_dev *rdev,
+ suspend_state_t state)
+{
+ struct mediatek_regulator_coupler *mrc = to_mediatek_coupler(coupler);
+ int max_spread = rdev->constraints->max_spread[0];
+ int vsram_min_uV = mrc->vsram_rdev->constraints->min_uV;
+ int vsram_max_uV = mrc->vsram_rdev->constraints->max_uV;
+ int vsram_target_min_uV, vsram_target_max_uV;
+ int min_uV = 0;
+ int max_uV = INT_MAX;
+ int ret;
+
+ /*
+ * If the target device is on, setting the SRAM voltage directly
+ * is not supported as it scales through its coupled supply voltage.
+ *
+ * An exception is made in case the use_count is zero: this means
+ * that this is the first time we power up the SRAM regulator, which
+ * implies that the target device has yet to perform initialization
+ * and setting a voltage at that time is harmless.
+ */
+ if (rdev == mrc->vsram_rdev) {
+ if (rdev->use_count == 0)
+ return regulator_do_balance_voltage(rdev, state, true);
+
+ return -EPERM;
+ }
+
+ ret = regulator_check_consumers(rdev, &min_uV, &max_uV, state);
+ if (ret < 0)
+ return ret;
+
+ if (min_uV == 0) {
+ ret = regulator_get_voltage_rdev(rdev);
+ if (ret < 0)
+ return ret;
+ min_uV = ret;
+ }
+
+ ret = regulator_check_voltage(rdev, &min_uV, &max_uV);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * If we're asked to set a voltage less than VSRAM min_uV, set
+ * the minimum allowed voltage on VSRAM, as in this case it is
+ * safe to ignore the max_spread parameter.
+ */
+ vsram_target_min_uV = max(vsram_min_uV, min_uV + max_spread);
+ vsram_target_max_uV = min(vsram_max_uV, vsram_target_min_uV + max_spread);
+
+ /* Make sure we're not out of range */
+ vsram_target_min_uV = min(vsram_target_min_uV, vsram_max_uV);
+
+ pr_debug("Setting voltage %d-%duV on %s (minuV %d)\n",
+ vsram_target_min_uV, vsram_target_max_uV,
+ rdev_get_name(mrc->vsram_rdev), min_uV);
+
+ ret = regulator_set_voltage_rdev(mrc->vsram_rdev, vsram_target_min_uV,
+ vsram_target_max_uV, state);
+ if (ret)
+ return ret;
+
+ /* The sram voltage is now balanced: update the target vreg voltage */
+ return regulator_do_balance_voltage(rdev, state, true);
+}
+
+static int mediatek_regulator_attach(struct regulator_coupler *coupler,
+ struct regulator_dev *rdev)
+{
+ struct mediatek_regulator_coupler *mrc = to_mediatek_coupler(coupler);
+ const char *rdev_name = rdev_get_name(rdev);
+
+ if (strstr(rdev_name, "sram")) {
+ if (mrc->vsram_rdev)
+ return -EINVAL;
+ mrc->vsram_rdev = rdev;
+ }
+
+ return 0;
+}
+
+static int mediatek_regulator_detach(struct regulator_coupler *coupler,
+ struct regulator_dev *rdev)
+{
+ struct mediatek_regulator_coupler *mrc = to_mediatek_coupler(coupler);
+
+ if (rdev == mrc->vsram_rdev) {
+ mrc->vsram_rdev = NULL;
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
+static struct mediatek_regulator_coupler mediatek_coupler = {
+ .coupler = {
+ .attach_regulator = mediatek_regulator_attach,
+ .detach_regulator = mediatek_regulator_detach,
+ .balance_voltage = mediatek_regulator_balance_voltage,
+ },
+};
+
+static int mediatek_regulator_coupler_init(void)
+{
+ if (!of_machine_is_compatible("mediatek,mt8183") &&
+ !of_machine_is_compatible("mediatek,mt8186") &&
+ !of_machine_is_compatible("mediatek,mt8192"))
+ return 0;
+
+ return regulator_coupler_register(&mediatek_coupler.coupler);
+}
+arch_initcall(mediatek_regulator_coupler_init);
+
+MODULE_DESCRIPTION("MediaTek Regulator Coupler driver");
+MODULE_LICENSE("GPL");
This driver currently deals with GPU-SRAM regulator coupling, ensuring that the SRAM voltage is always between a specific range of distance to the GPU voltage, depending on the SoC, necessary in order to achieve system stability across the full range of supported GPU frequencies. Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> --- Context: This driver is one of the pieces of a bigger puzzle, aiming to finally enable Dynamic Voltage/Frequency Scaling for Mali GPUs found on MediaTek SoCs on the fully open source graphics stack (Panfrost driver). No devicetree bindings are provided because this does not require any driver-specific binding at all. Last but not least: it was chosen to have this driver enabled for ( ARCH_MEDIATEK && REGULATOR ) without really giving a free configuration choice because, once the DVFS mechanism will be fully working, using one of the listed MediaTek SoCs *without* this coupling mechanism *will* lead to unstabilities and system crashes. For COMPILE_TEST, choice is given for obvious reasons. drivers/soc/mediatek/Kconfig | 5 + drivers/soc/mediatek/Makefile | 1 + drivers/soc/mediatek/mtk-regulator-coupler.c | 148 +++++++++++++++++++ 3 files changed, 154 insertions(+) create mode 100644 drivers/soc/mediatek/mtk-regulator-coupler.c