Re: [RESEND PATCH v3] soc: mediatek: Introduce mediatek-regulator-coupler driver
From: AngeloGioacchino Del Regno
Date: Mon Nov 21 2022 - 07:01:13 EST
Il 21/11/22 12:44, Matthias Brugger ha scritto:
On 06/10/2022 13:58, AngeloGioacchino Del Regno wrote:
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@xxxxxxxxxxxxx>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
---
This driver was successfully tested for more than 3 months.
GPU DVFS works correctly with no stability issues.
Changes in RESEND,v3:
Rebased over next-20221005
Changes in v3:
- Added braces to else-if branch
Changes in v2:
- Added check for n_coupled
- Added check for vgpu to enforce attaching to vgpu<->sram coupling only
Context:
This driver is the last 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 | 159 +++++++++++++++++++
3 files changed, 165 insertions(+)
create mode 100644 drivers/soc/mediatek/mtk-regulator-coupler.c
diff --git a/drivers/soc/mediatek/Kconfig b/drivers/soc/mediatek/Kconfig
index 40d0cc600cae..30b5afc0e51d 100644
--- a/drivers/soc/mediatek/Kconfig
+++ b/drivers/soc/mediatek/Kconfig
@@ -44,6 +44,11 @@ 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
diff --git a/drivers/soc/mediatek/Makefile b/drivers/soc/mediatek/Makefile
index 0e9e703c931a..8c0ddacbcde8 100644
--- a/drivers/soc/mediatek/Makefile
+++ b/drivers/soc/mediatek/Makefile
@@ -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
diff --git a/drivers/soc/mediatek/mtk-regulator-coupler.c
b/drivers/soc/mediatek/mtk-regulator-coupler.c
new file mode 100644
index 000000000000..ad2ed42aa697
--- /dev/null
+++ b/drivers/soc/mediatek/mtk-regulator-coupler.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Voltage regulators coupler for MediaTek SoCs
+ *
+ * Copyright (C) 2022 Collabora, Ltd.
+ * Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
+ */
+
+#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 we're getting a coupling of more than two regulators here and
+ * this means that this is surely not a GPU<->SRAM couple: in that
+ * case, we may want to use another coupler implementation, if any,
+ * or the generic one: the regulator core will keep walking through
+ * the list of couplers when any .attach_regulator() cb returns 1.
+ */
+ if (rdev->coupling_desc.n_coupled > 2)
+ return 1;
+
+ if (strstr(rdev_name, "sram")) {
My understanding is, that we have to have either a DT node with regulator-name =
"sram" property to pollute rdev->constraints->name or some regulator_desc->name
populated in the drivers/regulator/mt*.c
No, it's not trying to find a regulator named "sram", but any regulator that
*contains* the "sram" string in its name, but checks only regulators that are
coupled to others. This is the same for the "Vgpu" / "vgpu".
Example:
Regulator A, coupled to Regulator B.
Regulator A name = "Vgpu" or "vgpu", or *vgpu*, or *Vgpu*
(name must contain either Vgpu or vgpu)
Regulator B name = "vsram" or "sram_gpu" or *sram*
(name must contain "sram").
mrc->vsram_rdev = rdev
rdev == our Regulator B.
We hence return 0 to the coupling API: this will produce the effect of making
it use this driver's .balance_voltage() callback instead of the generic one
on vgpu<->vsram.
I wasn't able to find either of this, so I wonder how this is supposed to work.
Please provide pointers to a working and complete implementation of this, so that
I'm able to judge what is going on and if the approach is the correct one.
I tried to figure out using mt8195-tracking-master-rolling
That's the right branch.
Let's take MT8192 Asurada as an example of how this works....
`mt6359_vsram_others_ldo_reg´ is the SRAM regulator for the GPU:
https://gitlab.collabora.com/google/chromeos-kernel/-/blob/mt8195-tracking-master-rolling/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi#L551
`mt6359_vsram_others_ldo_reg` regulator-name = "vsram_others";
^^^^
Contains "sram", and this regulator is also
regulator-coupled-with = <&mt6315_7_vbuck1>;
`mt6315_7_vbuck1` regulator-name = "Vgpu";
^^^^
Contains "Vgpu", and this regulator is also
regulator-coupled-with = <&mt6359_vsram_others_ldo_reg>;
That's how the coupling works in this case.
Now, looking at case exclusions:
In MT8192 Asurada (or, actually, mt6359.dtsi) we have other regulators that do
actually contain "sram" in their name, like "vsram_proc1" and "vsram_others_sshub".
These regulators will be ignored, as they are *not* coupled with Vgpu.
What this driver currently does in this regard is:
1. Regulator attach is called only on *coupled* regulators, not on the others
2. If the regulator contains name "vgpu" or "Vgpu" or "sram" we're good,
otherwise we don't attach the balance_voltage logic of this driver to
the unmatched regulators.
Does this explanation clarify your doubts?
Regards,
Angelo