Re: [PATCH V2 3/5] backlight: qcom-wled: Add support for short circuit handling

Daniel Thompson
2018-05-08T10:35:54Z

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?

> +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?

> + 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
>