[PATCH v3] leds: flash: leds-qcom-flash: limit LED current based on thermal condition

From: Fenglin Wu via B4 Relay
Date: Thu Jun 06 2024 - 10:59:35 EST

From: Fenglin Wu <quic_fenglinw@xxxxxxxxxxx>

The flash module has status bits to indicate different thermal
conditions which are called as OTSTx. For each OTSTx status,
there is a recommended total flash current for all channels to
prevent the flash module entering into higher thermal level.
For example, the total flash current should be limited to 1000mA/500mA
respectively when the HW reaches the OTST1/OTST2 thermal level.

Signed-off-by: Fenglin Wu <quic_fenglinw@xxxxxxxxxxx>
---
Changes in v3:
- Fix coding style issues to address review comments in v2.
- Link to v2: https://lore.kernel.org/r/20240513-qcom_flash_thermal_derating-v2-1-e41a07d0eb83@xxxxxxxxxxx

Changes in v2:
- Update thermal threshold level 2 register definition for mvflash_4ch_regs.
Mvflash_4ch module thermal threshold level 2 configuration register
offset is 0x78, not succeeding from thermal threshold level 1 register 0x7a.
Hence it is not appropriate to use REG_FIELD_ID to define thermal threshold
register fileds like mvflash_3ch. Update to use REG_FIELD instead.
- Link to v1: https://lore.kernel.org/r/20240509-qcom_flash_thermal_derating-v1-1-1d5e68e5d71c@xxxxxxxxxxx
---
drivers/leds/flash/leds-qcom-flash.c | 163 ++++++++++++++++++++++++++++++++++-
1 file changed, 162 insertions(+), 1 deletion(-)

diff --git a/drivers/leds/flash/leds-qcom-flash.c b/drivers/leds/flash/leds-qcom-flash.c
index 7c99a3039171..aa22686fafe0 100644
--- a/drivers/leds/flash/leds-qcom-flash.c
+++ b/drivers/leds/flash/leds-qcom-flash.c
@@ -1,6 +1,6 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
- * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ * Copyright (c) 2022, 2024 Qualcomm Innovation Center, Inc. All rights reserved.
*/

#include <linux/bitfield.h>
@@ -14,6 +14,9 @@
#include <media/v4l2-flash-led-class.h>

/* registers definitions */
+#define FLASH_REVISION_REG 0x00
+#define FLASH_4CH_REVISION_V0P1 0x01
+
#define FLASH_TYPE_REG 0x04
#define FLASH_TYPE_VAL 0x18

@@ -73,6 +76,16 @@

#define UA_PER_MA 1000

+/* thermal threshold constants */
+#define OTST_3CH_MIN_VAL 3
+#define OTST1_4CH_MIN_VAL 0
+#define OTST1_4CH_V0P1_MIN_VAL 3
+#define OTST2_4CH_MIN_VAL 0
+
+#define OTST1_MAX_CURRENT_MA 1000
+#define OTST2_MAX_CURRENT_MA 500
+#define OTST3_MAX_CURRENT_MA 200
+
enum hw_type {
QCOM_MVFLASH_3CH,
QCOM_MVFLASH_4CH,
@@ -98,6 +111,9 @@ enum {
REG_IRESOLUTION,
REG_CHAN_STROBE,
REG_CHAN_EN,
+ REG_THERM_THRSH1,
+ REG_THERM_THRSH2,
+ REG_THERM_THRSH3,
REG_MAX_COUNT,
};

@@ -111,6 +127,9 @@ static struct reg_field mvflash_3ch_regs[REG_MAX_COUNT] = {
REG_FIELD(0x47, 0, 5), /* iresolution */
REG_FIELD_ID(0x49, 0, 2, 3, 1), /* chan_strobe */
REG_FIELD(0x4c, 0, 2), /* chan_en */
+ REG_FIELD(0x56, 0, 2), /* therm_thrsh1 */
+ REG_FIELD(0x57, 0, 2), /* therm_thrsh2 */
+ REG_FIELD(0x58, 0, 2), /* therm_thrsh3 */
};

static struct reg_field mvflash_4ch_regs[REG_MAX_COUNT] = {
@@ -123,6 +142,8 @@ static struct reg_field mvflash_4ch_regs[REG_MAX_COUNT] = {
REG_FIELD(0x49, 0, 3), /* iresolution */
REG_FIELD_ID(0x4a, 0, 6, 4, 1), /* chan_strobe */
REG_FIELD(0x4e, 0, 3), /* chan_en */
+ REG_FIELD(0x7a, 0, 2), /* therm_thrsh1 */
+ REG_FIELD(0x78, 0, 2), /* therm_thrsh2 */
};

struct qcom_flash_data {
@@ -130,9 +151,11 @@ struct qcom_flash_data {
struct regmap_field *r_fields[REG_MAX_COUNT];
struct mutex lock;
enum hw_type hw_type;
+ u32 total_ma;
u8 leds_count;
u8 max_channels;
u8 chan_en_bits;
+ u8 revision;
};

struct qcom_flash_led {
@@ -143,6 +166,7 @@ struct qcom_flash_led {
u32 max_timeout_ms;
u32 flash_current_ma;
u32 flash_timeout_ms;
+ u32 current_in_use_ma;
u8 *chan_id;
u8 chan_count;
bool enabled;
@@ -172,6 +196,127 @@ static int set_flash_module_en(struct qcom_flash_led *led, bool en)
return rc;
}

+static int update_allowed_flash_current(struct qcom_flash_led *led, u32 *current_ma, bool strobe)
+{
+ struct qcom_flash_data *flash_data = led->flash_data;
+ u32 therm_ma, avail_ma, thrsh[3], min_thrsh, sts;
+ int rc = 0;
+
+ mutex_lock(&flash_data->lock);
+ /*
+ * Put previously allocated current into allowed budget in either of these two cases:
+ * 1) LED is disabled;
+ * 2) LED is enabled repeatedly
+ */
+ if (!strobe || led->current_in_use_ma != 0) {
+ if (flash_data->total_ma >= led->current_in_use_ma)
+ flash_data->total_ma -= led->current_in_use_ma;
+ else
+ flash_data->total_ma = 0;
+
+ led->current_in_use_ma = 0;
+ if (!strobe)
+ goto unlock;
+ }
+
+ /*
+ * Cache the default thermal threshold settings, and set them to the lowest levels before
+ * reading over-temp real time status. If over-temp has been triggered at the lowest
+ * threshold, it's very likely that it would be triggered at a higher (default) threshold
+ * when more flash current is requested. Prevent device from triggering over-temp condition
+ * by limiting the flash current for the new request.
+ */
+ rc = regmap_field_read(flash_data->r_fields[REG_THERM_THRSH1], &thrsh[0]);
+ if (rc < 0)
+ goto unlock;
+
+ rc = regmap_field_read(flash_data->r_fields[REG_THERM_THRSH2], &thrsh[1]);
+ if (rc < 0)
+ goto unlock;
+
+ if (flash_data->hw_type == QCOM_MVFLASH_3CH) {
+ rc = regmap_field_read(flash_data->r_fields[REG_THERM_THRSH3], &thrsh[2]);
+ if (rc < 0)
+ goto unlock;
+ }
+
+ min_thrsh = OTST_3CH_MIN_VAL;
+ if (flash_data->hw_type == QCOM_MVFLASH_4CH)
+ min_thrsh = (flash_data->revision == FLASH_4CH_REVISION_V0P1) ?
+ OTST1_4CH_V0P1_MIN_VAL : OTST1_4CH_MIN_VAL;
+
+ rc = regmap_field_write(flash_data->r_fields[REG_THERM_THRSH1], min_thrsh);
+ if (rc < 0)
+ goto unlock;
+
+ if (flash_data->hw_type == QCOM_MVFLASH_4CH)
+ min_thrsh = OTST2_4CH_MIN_VAL;
+
+ /*
+ * The default thermal threshold settings have been updated hence
+ * restore them if any fault happens starting from here.
+ */
+ rc = regmap_field_write(flash_data->r_fields[REG_THERM_THRSH2], min_thrsh);
+ if (rc < 0)
+ goto restore;
+
+ if (flash_data->hw_type == QCOM_MVFLASH_3CH) {
+ rc = regmap_field_write(flash_data->r_fields[REG_THERM_THRSH3], min_thrsh);
+ if (rc < 0)
+ goto restore;
+ }
+
+ /* Read thermal level status to get corresponding derating flash current */
+ rc = regmap_field_read(flash_data->r_fields[REG_STATUS2], &sts);
+ if (rc)
+ goto restore;
+
+ therm_ma = FLASH_TOTAL_CURRENT_MAX_UA / 1000;
+ if (flash_data->hw_type == QCOM_MVFLASH_3CH) {
+ if (sts & FLASH_STS_3CH_OTST3)
+ therm_ma = OTST3_MAX_CURRENT_MA;
+ else if (sts & FLASH_STS_3CH_OTST2)
+ therm_ma = OTST2_MAX_CURRENT_MA;
+ else if (sts & FLASH_STS_3CH_OTST1)
+ therm_ma = OTST1_MAX_CURRENT_MA;
+ } else {
+ if (sts & FLASH_STS_4CH_OTST2)
+ therm_ma = OTST2_MAX_CURRENT_MA;
+ else if (sts & FLASH_STS_4CH_OTST1)
+ therm_ma = OTST1_MAX_CURRENT_MA;
+ }
+
+ /* Calculate the allowed flash current for the request */
+ if (therm_ma <= flash_data->total_ma)
+ avail_ma = 0;
+ else
+ avail_ma = therm_ma - flash_data->total_ma;
+
+ *current_ma = min_t(u32, *current_ma, avail_ma);
+ led->current_in_use_ma = *current_ma;
+ flash_data->total_ma += led->current_in_use_ma;
+
+ dev_dbg(led->flash.led_cdev.dev, "allowed flash current: %dmA, total current: %dmA\n",
+ led->current_in_use_ma, flash_data->total_ma);
+
+restore:
+ /* Restore to default thermal threshold settings */
+ rc = regmap_field_write(flash_data->r_fields[REG_THERM_THRSH1], thrsh[0]);
+ if (rc < 0)
+ goto unlock;
+
+ rc = regmap_field_write(flash_data->r_fields[REG_THERM_THRSH2], thrsh[1]);
+ if (rc < 0)
+ goto unlock;
+
+ if (flash_data->hw_type == QCOM_MVFLASH_3CH)
+ rc = regmap_field_write(flash_data->r_fields[REG_THERM_THRSH3], thrsh[2]);
+
+unlock:
+ mutex_unlock(&flash_data->lock);
+ return rc;
+}
+
static int set_flash_current(struct qcom_flash_led *led, u32 current_ma, enum led_mode mode)
{
struct qcom_flash_data *flash_data = led->flash_data;
@@ -313,6 +458,10 @@ static int qcom_flash_strobe_set(struct led_classdev_flash *fled_cdev, bool stat
if (rc)
return rc;

+ rc = update_allowed_flash_current(led, &led->flash_current_ma, state);
+ if (rc < 0)
+ return rc;
+
rc = set_flash_current(led, led->flash_current_ma, FLASH_MODE);
if (rc)
return rc;
@@ -429,6 +578,10 @@ static int qcom_flash_led_brightness_set(struct led_classdev *led_cdev,
if (rc)
return rc;

+ rc = update_allowed_flash_current(led, &current_ma, enable);
+ if (rc < 0)
+ return rc;
+
rc = set_flash_current(led, current_ma, TORCH_MODE);
if (rc)
return rc;
@@ -703,6 +856,14 @@ static int qcom_flash_led_probe(struct platform_device *pdev)
flash_data->hw_type = QCOM_MVFLASH_4CH;
flash_data->max_channels = 4;
regs = mvflash_4ch_regs;
+
+ rc = regmap_read(regmap, reg_base + FLASH_REVISION_REG, &val);
+ if (rc < 0) {
+ dev_err(dev, "Failed to read flash LED module revision, rc=%d\n", rc);
+ return rc;
+ }
+
+ flash_data->revision = val;
} else {
dev_err(dev, "flash LED subtype %#x is not yet supported\n", val);
return -ENODEV;

---
base-commit: ca66b10a11da3c445c9c0ca1184f549bbe9061f2
change-id: 20240507-qcom_flash_thermal_derating-260b1f3c757c

Best regards,
--
Fenglin Wu <quic_fenglinw@xxxxxxxxxxx>