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SubjectRe: [PATCH V4 7/8] backlight: qcom-wled: add support for short circuit handling
On 2018-07-20 19:37, Daniel Thompson wrote:
> On 09/07/18 11:22, 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>
>> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
>> ---
>> Changes from V3:
>> - Added Reviewed by tag.
>> - Addressed minor comments from Vinod
>>
>> drivers/video/backlight/qcom-wled.c | 132
>> ++++++++++++++++++++++++++++++++++--
>> 1 file changed, 128 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/video/backlight/qcom-wled.c
>> b/drivers/video/backlight/qcom-wled.c
>> index 362d254..a14f1a6 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>
>> @@ -64,6 +67,16 @@
>> #define WLED3_SINK_REG_STR_CABC(n) (0x66 + (n * 0x10))
>> #define WLED3_SINK_REG_STR_CABC_MASK BIT(7)
>> +/* WLED4 specific 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
>> +
>> /* WLED4 specific sink registers */
>> #define WLED4_SINK_REG_CURR_SINK 0x46
>> #define WLED4_SINK_REG_CURR_SINK_MASK GENMASK(7, 4)
>> @@ -113,17 +126,23 @@ 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 thread irq handler */
>> + ktime_t last_short_event;
>> u16 ctrl_addr;
>> u16 sink_addr;
>> u16 max_string_count;
>> u32 brightness;
>> u32 max_brightness;
>> + u32 short_count;
>> + bool disabled_by_short;
>> + bool has_short_detect;
>> struct wled_config cfg;
>> int (*wled_set_brightness)(struct wled *wled, u16 brightness);
>> @@ -174,6 +193,9 @@ static int wled_module_enable(struct wled *wled,
>> int val)
>> {
>> int rc;
>> + if (wled->disabled_by_short)
>> + return -EFAULT;
>
> EFAULT means bad address (memory fault). Perhaps EIO or maybe even
> something more exotic like ENXIO might be more appropriate?
>
>
>> +
>> rc = regmap_update_bits(wled->regmap, wled->ctrl_addr +
>> WLED_CTRL_REG_MOD_EN,
>> WLED_CTRL_REG_MOD_EN_MASK,
>> @@ -210,18 +232,19 @@ 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_sync_toggle(wled);
>> if (rc < 0) {
>> dev_err(wled->dev, "wled sync failed rc:%d\n", rc);
>> - return rc;
>> + goto unlock_mutex;
>> }
>> }
>> @@ -229,15 +252,61 @@ 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 USEC_PER_SEC
>> +
>> +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;
>
> Shouldn't this reset to 1 (e.g. we have just seen a short).
>
>
> Daniel.
Ok. I will change it in the next series.

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