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SubjectRe: [PATCH V2 3/5] backlight: qcom-wled: Add support for short circuit handling
On 2018-05-08 16:05, Daniel Thompson wrote:
> On Thu, May 03, 2018 at 03:42:30PM +0530, Kiran Gunda wrote:
>> Handle the short circuit interrupt and check if the short circuit
>> interrupt is valid. Re-enable the module to check if it goes
>> away. Disable the module altogether if the short circuit event
>> persists.
>>
>> Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>
>> ---
>> drivers/video/backlight/qcom-wled.c | 134
>> ++++++++++++++++++++++++++++++++++--
>> 1 file changed, 130 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/video/backlight/qcom-wled.c
>> b/drivers/video/backlight/qcom-wled.c
>> index be8b8d3..2cfba77 100644
>> --- a/drivers/video/backlight/qcom-wled.c
>> +++ b/drivers/video/backlight/qcom-wled.c
>> @@ -10,6 +10,9 @@
>> * GNU General Public License for more details.
>> */
>>
>> +#include <linux/delay.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/ktime.h>
>> #include <linux/kernel.h>
>> #include <linux/backlight.h>
>> #include <linux/module.h>
>> @@ -23,7 +26,9 @@
>>
>> #define WLED3_SINK_REG_BRIGHT_MAX 0xFFF
>>
>> -/* Control registers */
>> +/* WLED3 Control registers */
>> +#define WLED3_CTRL_REG_FAULT_STATUS 0x08
>> +
>> #define WLED3_CTRL_REG_MOD_EN 0x46
>> #define WLED3_CTRL_REG_MOD_EN_MASK BIT(7)
>>
>> @@ -36,7 +41,17 @@
>> #define WLED3_CTRL_REG_ILIMIT 0x4e
>> #define WLED3_CTRL_REG_ILIMIT_MASK GENMASK(2, 0)
>>
>> -/* sink registers */
>> +/* WLED4 control registers */
>> +#define WLED4_CTRL_REG_SHORT_PROTECT 0x5e
>> +#define WLED4_CTRL_REG_SHORT_EN_MASK BIT(7)
>> +
>> +#define WLED4_CTRL_REG_SEC_ACCESS 0xd0
>> +#define WLED4_CTRL_REG_SEC_UNLOCK 0xa5
>> +
>> +#define WLED4_CTRL_REG_TEST1 0xe2
>> +#define WLED4_CTRL_REG_TEST1_EXT_FET_DTEST2 0x09
>> +
>> +/* WLED3 sink registers */
>> #define WLED3_SINK_REG_SYNC 0x47
>> #define WLED3_SINK_REG_SYNC_MASK GENMASK(2, 0)
>> #define WLED4_SINK_REG_SYNC_MASK GENMASK(3, 0)
>> @@ -130,17 +145,23 @@ struct wled_config {
>> bool cs_out_en;
>> bool ext_gen;
>> bool cabc;
>> + bool external_pfet;
>> };
>>
>> struct wled {
>> const char *name;
>> struct device *dev;
>> struct regmap *regmap;
>> + struct mutex lock; /* Lock to avoid race from ISR */
>> + ktime_t last_short_event;
>> u16 ctrl_addr;
>> u16 sink_addr;
>> u32 brightness;
>> u32 max_brightness;
>> + u32 short_count;
>> const int *version;
>> + int short_irq;
>> + bool force_mod_disable;
>>
>> struct wled_config cfg;
>> int (*wled_set_brightness)(struct wled *wled, u16 brightness);
>> @@ -192,6 +213,9 @@ static int wled_module_enable(struct wled *wled,
>> int val)
>> {
>> int rc;
>>
>> + if (wled->force_mod_disable)
>> + return 0;
>> +
>> rc = regmap_update_bits(wled->regmap, wled->ctrl_addr +
>> WLED3_CTRL_REG_MOD_EN,
>> WLED3_CTRL_REG_MOD_EN_MASK,
>> @@ -248,12 +272,13 @@ static int wled_update_status(struct
>> backlight_device *bl)
>> bl->props.state & BL_CORE_FBBLANK)
>> brightness = 0;
>>
>> + mutex_lock(&wled->lock);
>> if (brightness) {
>> rc = wled->wled_set_brightness(wled, brightness);
>> if (rc < 0) {
>> dev_err(wled->dev, "wled failed to set brightness rc:%d\n",
>> rc);
>> - return rc;
>> + goto unlock_mutex;
>> }
>>
>> rc = wled->wled_sync_toggle(wled);
>> @@ -267,15 +292,60 @@ static int wled_update_status(struct
>> backlight_device *bl)
>> rc = wled_module_enable(wled, !!brightness);
>> if (rc < 0) {
>> dev_err(wled->dev, "wled enable failed rc:%d\n", rc);
>> - return rc;
>> + goto unlock_mutex;
>> }
>> }
>>
>> wled->brightness = brightness;
>>
>> +unlock_mutex:
>> + mutex_unlock(&wled->lock);
>> +
>> return rc;
>> }
>>
>> +#define WLED_SHORT_DLY_MS 20
>> +#define WLED_SHORT_CNT_MAX 5
>> +#define WLED_SHORT_RESET_CNT_DLY_US HZ
>
> So we think a short report every quarter second is harmless?
>
>
Yes. We wait for the short to report 5 times with in this time. If the
short
still persists, we go and disable the WLED module to avoid the damage.
This is
suggested by the HW team.

>> +static irqreturn_t wled_short_irq_handler(int irq, void *_wled)
>> +{
>> + struct wled *wled = _wled;
>> + int rc;
>> + s64 elapsed_time;
>> +
>> + wled->short_count++;
>> + mutex_lock(&wled->lock);
>> + rc = wled_module_enable(wled, false);
>> + if (rc < 0) {
>> + dev_err(wled->dev, "wled disable failed rc:%d\n", rc);
>> + goto unlock_mutex;
>> + }
>> +
>> + elapsed_time = ktime_us_delta(ktime_get(),
>> + wled->last_short_event);
>> + if (elapsed_time > WLED_SHORT_RESET_CNT_DLY_US)
>> + wled->short_count = 0;
>> +
>> + if (wled->short_count > WLED_SHORT_CNT_MAX) {
>> + dev_err(wled->dev, "Short trigged %d times, disabling WLED
>> forever!\n",
>> + wled->short_count);
>> + wled->force_mod_disable = true;
>> + goto unlock_mutex;
>> + }
>> +
>> + wled->last_short_event = ktime_get();
>> +
>> + msleep(WLED_SHORT_DLY_MS);
>> + rc = wled_module_enable(wled, true);
>> + if (rc < 0)
>> + dev_err(wled->dev, "wled enable failed rc:%d\n", rc);
>> +
>> +unlock_mutex:
>> + mutex_unlock(&wled->lock);
>> +
>> + return IRQ_HANDLED;
>> +}
>> +
>> static int wled3_setup(struct wled *wled)
>> {
>> u16 addr;
>> @@ -435,6 +505,21 @@ static int wled4_setup(struct wled *wled)
>> return rc;
>> }
>>
>> + if (wled->cfg.external_pfet) {
>> + /* Unlock the secure register access */
>> + rc = regmap_write(wled->regmap, wled->ctrl_addr +
>> + WLED4_CTRL_REG_SEC_ACCESS,
>> + WLED4_CTRL_REG_SEC_UNLOCK);
>> + if (rc < 0)
>> + return rc;
>> +
>> + rc = regmap_write(wled->regmap,
>> + wled->ctrl_addr + WLED4_CTRL_REG_TEST1,
>> + WLED4_CTRL_REG_TEST1_EXT_FET_DTEST2);
>> + if (rc < 0)
>> + return rc;
>> + }
>> +
>> return 0;
>> }
>>
>> @@ -446,6 +531,7 @@ static int wled4_setup(struct wled *wled)
>> .switch_freq = 11,
>> .enabled_strings = 0xf,
>> .cabc = false,
>> + .external_pfet = true,
>> };
>>
>> static const u32 wled3_boost_i_limit_values[] = {
>> @@ -628,6 +714,7 @@ static int wled_configure(struct wled *wled)
>> { "qcom,cs-out", &cfg->cs_out_en, },
>> { "qcom,ext-gen", &cfg->ext_gen, },
>> { "qcom,cabc", &cfg->cabc, },
>> + { "qcom,external-pfet", &cfg->external_pfet, },
>> };
>>
>> prop_addr = of_get_address(dev->of_node, 0, NULL, NULL);
>> @@ -701,6 +788,39 @@ static int wled_configure(struct wled *wled)
>> return 0;
>> }
>>
>> +static int wled_configure_short_irq(struct wled *wled,
>> + struct platform_device *pdev)
>> +{
>> + int rc = 0;
>> +
>> + /* PM8941 doesn't have the short detection support */
>> + if (*wled->version == WLED_PM8941)
>> + return 0;
>> +
>> + rc = regmap_update_bits(wled->regmap, wled->ctrl_addr +
>> + WLED4_CTRL_REG_SHORT_PROTECT,
>> + WLED4_CTRL_REG_SHORT_EN_MASK,
>> + WLED4_CTRL_REG_SHORT_EN_MASK);
>> + if (rc < 0)
>> + return rc;
>> +
>> + wled->short_irq = platform_get_irq_byname(pdev, "short");
>> + if (wled->short_irq < 0) {
>> + dev_dbg(&pdev->dev, "short irq is not used\n");
>> + return 0;
>> + }
>> +
>> + rc = devm_request_threaded_irq(wled->dev, wled->short_irq,
>> + NULL, wled_short_irq_handler,
>
> NULL? There's no register we can check to make sure the interrupt
> handler did not enter spuriously?
>
>
There is FAULT_STATUS register. I will address it in the next series.

>> + IRQF_ONESHOT,
>> + "wled_short_irq", wled);
>> + if (rc < 0)
>> + dev_err(wled->dev, "Unable to request short_irq (err:%d)\n",
>> + rc);
>> +
>> + return rc;
>> +}
>> +
>> static const struct backlight_ops wled_ops = {
>> .update_status = wled_update_status,
>> };
>> @@ -733,6 +853,8 @@ static int wled_probe(struct platform_device
>> *pdev)
>> return -ENODEV;
>> }
>>
>> + mutex_init(&wled->lock);
>> +
>> rc = wled_configure(wled);
>> if (rc)
>> return rc;
>> @@ -752,6 +874,10 @@ static int wled_probe(struct platform_device
>> *pdev)
>> }
>> }
>>
>> + rc = wled_configure_short_irq(wled, pdev);
>> + if (rc < 0)
>> + return rc;
>> +
>> val = WLED_DEFAULT_BRIGHTNESS;
>> of_property_read_u32(pdev->dev.of_node, "default-brightness", &val);
>>
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
>> Forum,
>> a Linux Foundation Collaborative Project
>>

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