Hi Fenglin,

On Fri, Jul 17, 2026 at 12:29:01AM -0700, Fenglin Wu wrote:

Please use "error" or "err" for such variables that hold error codes.

+
+	ret = cfg_write(h, HAP_CFG_TLRA_OL_HIGH_REG, (tmp >> 8) & TLRA_OL_MSB_MASK);
+	if (ret)
+		return ret;
+
+	return cfg_write(h, HAP_CFG_TLRA_OL_LOW_REG, tmp & 0xFF);

Explicit error handling and "return 0;" in cases where there are
multiple failure points.

+}
+
+static int haptics_enable_module(struct qcom_haptics *h, bool enable)
+{
+	return cfg_update_bits(h, HAP_CFG_EN_CTL_REG, HAPTICS_EN_BIT,
+			       enable ? HAPTICS_EN_BIT : 0);
+}
+
+static int haptics_configure_autores(struct qcom_haptics *h)
+{
+	int ret;
+
+	/* AUTORES_CFG: enable, 10-cycle delay, 25% error window */
+	ret = cfg_write(h, HAP_CFG_AUTORES_CFG_REG,
+			AUTORES_EN_BIT |
+			FIELD_PREP(AUTORES_EN_DLY_MASK, AUTORES_EN_DLY_CYCLES) |
+			FIELD_PREP(AUTORES_ERR_WIN_MASK, AUTORES_ERR_WIN_25PCT));
+	if (ret)
+		return ret;
+
+	/* DRV_DUTY: adaptive drive/brake duty cycles at 62.5% */
+	ret = cfg_write(h, HAP_CFG_DRV_DUTY_CFG_REG,
+			ADT_DRV_DUTY_EN_BIT | ADT_BRK_DUTY_EN_BIT |
+			FIELD_PREP(DRV_DUTY_MASK, AUTORES_DRV_DUTY_62P5) |
+			FIELD_PREP(BRK_DUTY_MASK, AUTORES_BRK_DUTY_62P5));
+	if (ret)
+		return ret;
+
+	/* Pre-HIZ delay: 10 µs */
+	ret = cfg_write(h, HAP_CFG_RAMP_DN_CFG2_REG, AUTORES_PRE_HIZ_DLY_10US);
+	if (ret)
+		return ret;
+
+	/* Zero-cross window: debounce 3, no hysteresis, height 2 */
+	return cfg_write(h, HAP_CFG_ZX_WIND_CFG_REG,
+			 FIELD_PREP(ZX_DEBOUNCE_MASK, AUTORES_ZX_DEBOUNCE) |
+			 FIELD_PREP(ZX_WIN_HEIGHT_MASK, AUTORES_ZX_WIN_HEIGHT));
+}
+
+static int haptics_write_fifo_chunk(struct qcom_haptics *h,
+				    const s8 *data, u32 len)
+{
+	u32 bulk_len = ALIGN_DOWN(len, 4);
+	int i, ret;
+
+	/*
+	 * FIFO data writing supports both 4-byte bulk writes using registers
+	 * [HAP_PTN_FIFO_DIN_0_REG ... HAP_PTN_FIFO_DIN_3_REG], and 1-byte writes
+	 * using the HAP_PTN_FIFO_DIN_1B_REG register. The 4-byte bulk write is more
+	 * efficient, so use 4-byte writes for the initial 4-byte aligned data,
+	 * and 1-byte writes for any trailing remainder.
+	 */
+	for (i = 0; i < bulk_len; i += 4) {
+		ret = ptn_bulk_write(h, HAP_PTN_FIFO_DIN_0_REG, &data[i], 4);
+		if (ret)
+			return ret;
+	}
+
+	for (; i < len; i++) {
+		ret = ptn_write(h, HAP_PTN_FIFO_DIN_1B_REG, (u8)data[i]);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int haptics_configure_fifo_mmap(struct qcom_haptics *h)
+{
+	u32 fifo_len, fifo_units;
+
+	/* Config all memory space for FIFO usage for now */
+	fifo_len = HAP530_MEM_TOTAL_BYTES;
+	fifo_len = ALIGN_DOWN(fifo_len, 64);
+	fifo_units = fifo_len / 64;
+	h->fifo_len = fifo_len;
+
+	return ptn_write(h, HAP_PTN_MMAP_FIFO_REG,
+			 MMAP_FIFO_EXIST_BIT |
+			 FIELD_PREP(MMAP_FIFO_LEN_MASK, fifo_units - 1));
+}
+
+static u32 haptics_gain_scaled_vmax(struct qcom_haptics *h, u32 vmax_mv)
+{
+	u16 gain = atomic_read(&h->gain);
+	u32 v = mult_frac(vmax_mv, gain, 0xFFFF);
+
+	return max_t(u32, v, VMAX_STEP_MV);
+}
+
+static void haptics_fifo_irq_enable(struct qcom_haptics *h, bool enable)
+{
+	if (h->irq_enabled == enable)
+		return;

Should t you know if given code runs with interrupts disabled or
enabled? I believe this tracking and the wrapper should be removed.

+
+	if (enable)
+		enable_irq(h->fifo_empty_irq);
+	else
+		disable_irq(h->fifo_empty_irq);
+
+	h->irq_enabled = enable;
+}
+
+static int haptics_enqueue_play_req(struct qcom_haptics *h, int effect_id, bool play)
+{
+	struct haptics_play_req *req;
+
+	guard(spinlock_irqsave)(&h->play_queue_lock);
+
+	/*
+	 * Coalesce with an already queued request for
+	 * the same effect instead of appending.
+	 */
+	list_for_each_entry(req, &h->play_queue, node) {
+		if (req->effect_id == effect_id) {
+			req->play = play;
+			return 0;
+		}
+	}
+
+	req = kmalloc_obj(*req, GFP_ATOMIC);
+	if (!req)
+		return -ENOMEM;
+
+	req->effect_id = effect_id;
+	req->play = play;
+
+	list_add_tail(&req->node, &h->play_queue);
+
+	return 0;
+}
+
+static struct haptics_play_req *haptics_dequeue_play_req(struct qcom_haptics *h)
+{
+	struct haptics_play_req *req = NULL;
+
+	guard(spinlock_irqsave)(&h->play_queue_lock);
+
+	if (!list_empty(&h->play_queue)) {
+		req = list_first_entry(&h->play_queue, struct haptics_play_req, node);
+		list_del(&req->node);
+	}
+
+	return req;
+}
+
+static bool haptics_queue_pending(struct qcom_haptics *h)
+{
+	guard(spinlock_irqsave)(&h->play_queue_lock);
+
+	return !list_empty(&h->play_queue);

I strongly dislike this kind of functions since their result is
obsolete the moment they return. Sometimes it is OK, but usually it
isn't. In this driver I think it is fine, but I would much rather inline
this into the caller and added comment. We can also schedule work
holding this spinlock I think...

+}
+
+static void haptics_queue_remove_effect(struct qcom_haptics *h, int effect_id)
+{
+	struct haptics_play_req *req, *tmp;
+
+	guard(spinlock_irqsave)(&h->play_queue_lock);
+
+	list_for_each_entry_safe(req, tmp, &h->play_queue, node) {
+		if (req->effect_id == effect_id) {
+			list_del(&req->node);
+			kfree(req);
+		}
+	}
+}
+
+static void haptics_queue_flush(struct qcom_haptics *h)
+{
+	struct haptics_play_req *req, *tmp;
+
+	guard(spinlock_irqsave)(&h->play_queue_lock);
+
+	list_for_each_entry_safe(req, tmp, &h->play_queue, node) {
+		list_del(&req->node);
+		kfree(req);
+	}
+}
+
+static int haptics_start_direct_play(struct qcom_haptics *h, int effect_id)
+{
+	struct qcom_haptics_effect *eff = &h->effects[effect_id];
+	int ret;
+
+	ret = haptics_clear_faults(h);
+	if (ret)
+		return ret;
+
+	/* Enable auto-resonance for DIRECT_PLAY mode */
+	ret = cfg_update_bits(h, HAP_CFG_AUTORES_CFG_REG,
+			      AUTORES_EN_BIT, AUTORES_EN_BIT);
+	if (ret)
+		return ret;
+
+	ret = haptics_set_vmax(h, haptics_gain_scaled_vmax(h, h->vmax_mv));
+	if (ret)
+		return ret;
+
+	ret = ptn_write(h, HAP_PTN_DIRECT_PLAY_REG, eff->amplitude);
+	if (ret)
+		return ret;
+
+	return cfg_write(h, HAP_CFG_SPMI_PLAY_REG,
+			 PLAY_EN_BIT | FIELD_PREP(PAT_SRC_MASK, PAT_SRC_DIRECT_PLAY));
+}
+
+static int haptics_start_fifo(struct qcom_haptics *h, int effect_id)
+{
+	struct qcom_haptics_effect *eff = &h->effects[effect_id];
+	u32 vmax = eff->vmax_mv ? eff->vmax_mv : h->vmax_mv;
+	u32 init_len;
+	bool data_done;
+	int ret;
+
+	if (!eff->fifo_data || !eff->data_len)
+		return -EINVAL;
+
+	ret = haptics_clear_faults(h);
+	if (ret)
+		return ret;
+
+	/* Disable auto-resonance for FIFO mode */
+	ret = cfg_update_bits(h, HAP_CFG_AUTORES_CFG_REG, AUTORES_EN_BIT, 0);
+	if (ret)
+		return ret;
+
+	ret = haptics_set_vmax(h, haptics_gain_scaled_vmax(h, vmax));
+	if (ret)
+		return ret;
+
+	ret = ptn_update_bits(h, HAP_PTN_FIFO_PLAY_RATE_REG,
+			      FIFO_PLAY_RATE_MASK,
+			      FIELD_PREP(FIFO_PLAY_RATE_MASK, eff->play_rate));
+	if (ret)
+		return ret;
+
+	/* Flush FIFO before loading new data */
+	ret = ptn_write(h, HAP_PTN_MEM_OP_ACCESS_REG, MEM_FLUSH_RELOAD_BIT);
+	if (ret)
+		return ret;
+	ret = ptn_write(h, HAP_PTN_MEM_OP_ACCESS_REG, 0);
+	if (ret)
+		return ret;
+
+	guard(mutex)(&h->fifo_lock);
+
+	/* Write the initial chunk and initialise streaming state */
+	init_len = min_t(u32, eff->data_len, FIFO_INIT_FILL);
+	ret = haptics_write_fifo_chunk(h, eff->fifo_data, init_len);
+	if (ret)
+		return ret;
+
+	h->fifo_data    = eff->fifo_data;
+	h->data_len     = eff->data_len;
+	h->data_written = init_len;
+
+	/*
+	 * Set empty threshold.  When threshold > 0 the hardware fires the
+	 * FIFO-empty interrupt when occupancy drops below the threshold,
+	 * allowing the driver to refill.
+	 */
+	data_done = (h->data_written >= h->data_len);
+	if (!data_done) {
+		ret = ptn_write(h, HAP_PTN_FIFO_EMPTY_CFG_REG,
+				FIFO_EMPTY_THRESH / FIFO_THRESH_LSB);
+		if (ret) {
+			dev_err(h->dev, "set FIFO empty threshold failed, ret=%d\n", ret);
+			h->fifo_data = NULL;
+			return ret;
+		}
+
+		haptics_fifo_irq_enable(h, true);
+	}
+
+	ret = cfg_write(h, HAP_CFG_SPMI_PLAY_REG,
+			 PLAY_EN_BIT | FIELD_PREP(PAT_SRC_MASK, PAT_SRC_FIFO));
+	if (ret) {
+		dev_err(h->dev, "trigger FIFO play failed, ret=%d\n", ret);
+		ptn_write(h, HAP_PTN_FIFO_EMPTY_CFG_REG, 0);
+		/*
+		 * HW play never started since this SPMI write itself failed,
+		 * and the FIFO empty IRQ has never fired, so disabling the
+		 * IRQ synchronously here can't deadlock against 'fifo_lock'.
+		 */
+		haptics_fifo_irq_enable(h, false);
+		h->fifo_data = NULL;
+		return ret;
+	}
+
+	return 0;
+}
+
+/*
+ * haptics_fifo_empty_irq: Threaded IRQ handler for the FIFO-empty interrupt.
+ *
+ * While a FIFO play is in progress the hardware fires this interrupt when
+ * the number of samples in the FIFO drops below the programmed threshold.
+ * The handler refills the FIFO from the effect's data buffer.  When all
+ * samples have been written the threshold is set to zero. The HW would
+ * stop the play automatically after all of the samples in FIFO memory are
+ * played out.
+ */
+static irqreturn_t haptics_fifo_empty_irq(int irq, void *dev_id)
+{
+	struct qcom_haptics *h = dev_id;
+	u32 sts, to_write;
+	int ret;
+
+	ret = regmap_read(h->regmap,
+			  h->cfg_base + HAP_CFG_INT_RT_STS_REG, &sts);
+	if (ret || !(sts & FIFO_EMPTY_BIT))
+		return IRQ_HANDLED;
+
+	guard(mutex)(&h->fifo_lock);
+
+	if (!h->fifo_data)
+		return IRQ_HANDLED;
+
+	/* Refill: write the next chunk */
+	to_write = min_t(u32, h->data_len - h->data_written,
+			 h->fifo_len - FIFO_EMPTY_THRESH);
+	ret = haptics_write_fifo_chunk(h, &h->fifo_data[h->data_written], to_write);
+	if (ret) {
+		dev_err(h->dev, "refill FIFO samples failed, ret=%d\n", ret);
+		/*
+		 * If data refilling is failed,stop the HW play and disable the
+		 * IRQ to prevent the FIFO empty IRQ being fired continuously.
+		 */

Is recovery possible after this?

+		cfg_write(h, HAP_CFG_SPMI_PLAY_REG, 0);
+		disable_irq_nosync(h->fifo_empty_irq);
+		h->irq_enabled = false;
+		return IRQ_HANDLED;
+	}
+
+	h->data_written += to_write;
+
+	/* Disable the interrupt after all the data is queued */
+	if (h->data_written >= h->data_len)
+		ptn_write(h, HAP_PTN_FIFO_EMPTY_CFG_REG, 0);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * haptics_stop_locked: stop play in HW and put runtime PM
+ * @h:	haptics device
+ * @put_noidle:	a flag to put noidle
+ *
+ * Stop HW play, clear the FIFO data if the active effect was FIFO-mode, and
+ * put runtime PM into either noidle or autosuspend based on put_noidle flag.
+ *
+ * Must be called with play_lock held.

Maybe add lockdep_assert_held() instead of comments/naming?

+ */
+static void haptics_stop_locked(struct qcom_haptics *h, bool put_noidle)
+{
+	cfg_write(h, HAP_CFG_SPMI_PLAY_REG, 0);
+
+	if (h->active_mode == HAPTICS_FIFO) {
+		ptn_write(h, HAP_PTN_FIFO_EMPTY_CFG_REG, 0);
+		haptics_fifo_irq_enable(h, false);
+		scoped_guard(mutex, &h->fifo_lock) {
+			h->fifo_data = NULL;
+		}
+	}
+
+	h->active_effect_id = -1;
+	h->active_mode = HAPTICS_MODE_NONE;
+
+	if (h->pm_ref_held) {
+		if (put_noidle)
+			pm_runtime_put_noidle(h->dev);
+		else
+			pm_runtime_put_autosuspend(h->dev);
+
+		h->pm_ref_held = false;
+	}
+}
+
+/*
+ * haptics_start_locked: start to play an effect
+ * @h:	haptics device
+ * @effect_id:	the index of the effect
+ *
+ * If an effect is currently active, stop it 1st. Acquires a PM ref
+ * if not already held, and then trigger the play based on the
+ * play mode. Update active_effect_id/active_mode on success.
+ *
+ * Must be called with play_lock held.
+ */
+static int haptics_start_locked(struct qcom_haptics *h, int effect_id)
+{
+	int ret;
+
+	if (h->active_effect_id != -1)
+		haptics_stop_locked(h, false);
+
+	if (!h->pm_ref_held) {
+		ret = pm_runtime_resume_and_get(h->dev);
+		if (ret < 0) {
+			dev_err(h->dev, "failed to resume device: %d\n", ret);
+			return ret;
+		}
+
+		h->pm_ref_held = true;
+	}
+
+	switch (h->effects[effect_id].mode) {
+	case HAPTICS_DIRECT_PLAY:
+		ret = haptics_start_direct_play(h, effect_id);
+		break;
+	case HAPTICS_FIFO:
+		ret = haptics_start_fifo(h, effect_id);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	if (ret) {
+		dev_err(h->dev, "failed to start effect %d: %d\n", effect_id, ret);
+		if (h->pm_ref_held) {
+			pm_runtime_put_autosuspend(h->dev);
+			h->pm_ref_held = false;
+		}
+
+		return ret;
+	}
+
+	h->active_effect_id = effect_id;
+	h->active_mode = h->effects[effect_id].mode;
+
+	return 0;
+}
+
+static void haptics_play_work(struct work_struct *work)
+{
+	struct qcom_haptics *h = container_of(to_delayed_work(work),
+					      struct qcom_haptics, play_work);
+	struct haptics_play_req *req = haptics_dequeue_play_req(h);
+	bool rearmed = false;
+	u32 length_us;
+	int ret;
+
+	guard(mutex)(&h->play_lock);
+
+	/* No valid request available */
+	if (req == NULL)

	if (!req)

+		return;
+
+	if (req->play) {
+		ret = haptics_start_locked(h, req->effect_id);
+		if (ret) {
+			dev_err(h->dev, "play haptics failed, ret=%d\n", ret);
+		} else {
+			/*
+			 * Re-arm the work to stop the play or advance
+			 * to next play after the play duration
+			 */
+			length_us = h->effects[req->effect_id].length_us;
+			if (length_us) {
+				schedule_delayed_work(&h->play_work,
+						      usecs_to_jiffies(length_us));
+				rearmed = true;
+			}
+		}
+	} else {
+		if (req->effect_id != h->active_effect_id)
+			dev_warn(h->dev, "effect %d is not under playing\n", req->effect_id);
+		else
+			haptics_stop_locked(h, false);
+	}
+
+	kfree(req);
+
+	/*
+	 * Handle the remaining requests if doesn't need to wait
+	 */
+	if (!rearmed && haptics_queue_pending(h))
+		schedule_delayed_work(&h->play_work, 0);
+}
+
+static void haptics_clear_effect(struct qcom_haptics *h,
+				 struct qcom_haptics_effect *effect)
+{
+	guard(mutex)(&h->fifo_lock);
+
+	if (h->fifo_data == effect->fifo_data)
+		h->fifo_data = NULL;
+
+	kvfree(effect->fifo_data);
+	effect->fifo_data = NULL;
+	effect->data_len  = 0;
+}
+
+/*
+ * haptics_fifo_length_us: Calculate the play duration of a FIFO effect.
+ * @h:	haptics device pointer
+ * @rate: FIFO data play rate
+ * @data_len: FFO data length
+ *
+ * Each FIFO sample is played out over one play-rate period, so the total
+ * duration is the number of samples times that period:
+ *
+ *   length_us = (clk_base * data_len * multiplier) / divider
+ *
+ * For T_LRA-based rates the period derives from the LRA resonance period
+ * (h->t_lra_us): DIV_2/4/8 shorten it, X_2/4/8 lengthen it.  For the
+ * kHz-based rates the period is 1000 us / freq_khz.
+ */
+static u32 haptics_fifo_length_us(struct qcom_haptics *h,
+				  enum qcom_haptics_play_rate rate,
+				  u32 data_len)
+{
+	u32 clk_base = 1000, multiplier = 1, divider = 1;
+
+	switch (rate) {
+	case PLAY_RATE_T_LRA:
+		clk_base = h->t_lra_us;
+		break;
+	case PLAY_RATE_T_LRA_DIV_2:
+		clk_base = h->t_lra_us;
+		divider = 2;
+		break;
+	case PLAY_RATE_T_LRA_DIV_4:
+		clk_base = h->t_lra_us;
+		divider = 4;
+		break;
+	case PLAY_RATE_T_LRA_DIV_8:
+		clk_base = h->t_lra_us;
+		divider = 8;
+		break;
+	case PLAY_RATE_T_LRA_X_2:
+		clk_base = h->t_lra_us;
+		multiplier = 2;
+		break;
+	case PLAY_RATE_T_LRA_X_4:
+		clk_base = h->t_lra_us;
+		multiplier = 4;
+		break;
+	case PLAY_RATE_T_LRA_X_8:
+		clk_base = h->t_lra_us;
+		multiplier = 8;
+		break;
+	case PLAY_RATE_F_8KHZ:
+		divider = 8;
+		break;
+	case PLAY_RATE_F_16KHZ:
+		divider = 16;
+		break;
+	case PLAY_RATE_F_24KHZ:
+		divider = 24;
+		break;
+	case PLAY_RATE_F_32KHZ:
+		divider = 32;
+		break;
+	case PLAY_RATE_F_44P1KHZ:
+		clk_base *= 10;
+		divider = 441;
+		break;
+	case PLAY_RATE_F_48KHZ:
+		divider = 48;
+		break;
+	default:
+		/* Unexpected rate: fall back to the resonance period. */
+		clk_base = h->t_lra_us;
+		break;
+	}
+
+	return div_u64((u64)clk_base * data_len * multiplier, divider);
+}
+
+static int haptics_upload_effect(struct input_dev *dev,
+				 struct ff_effect *effect,
+				 struct ff_effect *old)
+{
+	struct qcom_haptics *h = input_get_drvdata(dev);
+	struct qcom_haptics_effect *priv;
+	int id = effect->id;
+	u32 data_len, level;
+	s8 *fifo;
+
+	s16 *buf __free(kvfree) = NULL;
+
+	guard(mutex)(&h->play_lock);
+
+	if (id < 0 || id >= HAPTICS_MAX_EFFECTS)
+		return -EINVAL;
+
+	if (id == h->active_effect_id) {
+		dev_err(h->dev, "effect %d is under playing\n", id);
+		return -EBUSY;
+	}
+
+	priv = &h->effects[id];
+
+	switch (effect->type) {
+	case FF_CONSTANT:
+		haptics_clear_effect(h, priv);
+		level = effect->u.constant.level <= 0 ? 0 : effect->u.constant.level;
+		priv->amplitude = (u8)mult_frac(level, 255, 0x7FFF);
+		priv->length_us = effect->replay.length * USEC_PER_MSEC;
+		priv->mode = HAPTICS_DIRECT_PLAY;
+		return 0;
+
+	case FF_PERIODIC:
+		if (effect->u.periodic.waveform != FF_CUSTOM)
+			return -EINVAL;
+		/*
+		 * Minimum 3 elements: play-rate code + vmax + at least one sample.
+		 * Limit the maximum data length to ~48K so that it can at least
+		 * handle ~1s vibration at the fast (48K) play rate.
+		 */
+		if (effect->u.periodic.custom_len < 3 ||
+		    effect->u.periodic.custom_len > CUSTOM_DATA_MAX_LEN + 2)
+			return -EINVAL;
+
+		buf = vmemdup_array_user(effect->u.periodic.custom_data,
+					effect->u.periodic.custom_len,
+					sizeof(s16));
+		if (IS_ERR(buf))
+			return PTR_ERR(no_free_ptr(buf));
+
+		if (buf[CUSTOM_DATA_RATE_IDX] < 0 ||
+		    buf[CUSTOM_DATA_RATE_IDX] > PLAY_RATE_MAX ||
+		    buf[CUSTOM_DATA_RATE_IDX] == PLAY_RATE_RESERVED)
+			return -EINVAL;
+
+		data_len = effect->u.periodic.custom_len - CUSTOM_DATA_SAMPLE_START;
+
+		fifo = kvmalloc(data_len, GFP_KERNEL);
+		if (!fifo)
+			return -ENOMEM;
+
+		/* Pack: one s8 sample per s16 slot (lower byte) */
+		for (int i = 0; i < data_len; i++)
+			fifo[i] = (s8)buf[CUSTOM_DATA_SAMPLE_START + i];
+
+		haptics_clear_effect(h, priv);
+
+		scoped_guard(mutex, &h->fifo_lock) {
+			priv->fifo_data = fifo;
+			priv->data_len = data_len;
+		}
+
+		priv->play_rate = (u8)buf[CUSTOM_DATA_RATE_IDX];
+		priv->vmax_mv   = (u32)clamp_val(buf[CUSTOM_DATA_VMAX_IDX], 0, VMAX_MV_MAX);
+		priv->length_us = haptics_fifo_length_us(h, priv->play_rate, data_len);
+		priv->mode = HAPTICS_FIFO;
+
+		return 0;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int haptics_playback(struct input_dev *dev, int effect_id, int val)
+{
+	struct qcom_haptics *h = input_get_drvdata(dev);
+	int ret;
+
+	ret = haptics_enqueue_play_req(h, effect_id, val > 0);
+	if (ret)
+		return ret;
+
+	if (val > 0)
+		/*
+		 * Queue the play.  If a duration re-arm is already pending this
+		 * is a no-op, so the new play waits for the current effect to
+		 * finish before the worker dequeues it.
+		 */
+		schedule_delayed_work(&h->play_work, 0);
+	else
+		/*
+		 * Run the worker now, cancelling any pending duration re-arm,
+		 * so an explicit stop takes effect immediately.
+		 */
+		mod_delayed_work(system_percpu_wq, &h->play_work, 0);
+
+	return 0;
+}
+
+static int haptics_erase(struct input_dev *dev, int effect_id)
+{
+	struct qcom_haptics *h = input_get_drvdata(dev);
+	struct qcom_haptics_effect *priv = &h->effects[effect_id];
+
+	guard(mutex)(&h->play_lock);
+
+	haptics_queue_remove_effect(h, effect_id);
+
+	if (h->active_effect_id == effect_id)
+		haptics_stop_locked(h, false);
+
+	haptics_clear_effect(h, priv);
+	priv->mode = HAPTICS_MODE_NONE;
+
+	return 0;
+}
+
+static void haptics_set_gain(struct input_dev *dev, u16 gain)
+{
+	struct qcom_haptics *h = input_get_drvdata(dev);
+
+	atomic_set(&h->gain, gain);

You need to adjust currently played effects here: new gain should take
effect immediately.

+}
+
+static int qcom_haptics_probe(struct platform_device *pdev)
+{
+	struct qcom_haptics *h;
+	struct input_dev *input;
+	struct ff_device *ff;
+	u32 regs[2], vmax_uv;
+	int ret, irq;
+
+	h = devm_kzalloc(&pdev->dev, sizeof(*h), GFP_KERNEL);
+	if (!h)
+		return -ENOMEM;
+
+	h->dev = &pdev->dev;
+
+	h->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!h->regmap)
+		return dev_err_probe(h->dev, -ENODEV, "no regmap from parent\n");
+
+	ret = device_property_read_u32_array(h->dev, "reg", regs, ARRAY_SIZE(regs));
+	if (ret)
+		return dev_err_probe(h->dev, ret, "failed to read 'reg' property\n");
+
+	h->cfg_base = regs[0];
+	h->ptn_base = regs[1];
+
+	ret = device_property_read_u32(h->dev, "qcom,lra-period-us", &h->t_lra_us);
+	if (ret)
+		return dev_err_probe(h->dev, ret, "missing qcom,lra-period-us\n");
+
+	h->t_lra_us = clamp(h->t_lra_us, (u32)TLRA_STEP_US, (u32)TLRA_US_MAX);
+
+	ret = device_property_read_u32(h->dev, "qcom,vmax-microvolt", &vmax_uv);
+	if (ret)
+		return dev_err_probe(h->dev, ret, "missing qcom,vmax-microvolt\n");
+
+	h->vmax_mv = clamp(vmax_uv / 1000, (u32)VMAX_STEP_MV, (u32)VMAX_MV_MAX);
+
+	ret = haptics_config_lra_period(h);
+	if (ret)
+		return ret;
+
+	ret = haptics_configure_autores(h);
+	if (ret)
+		return ret;
+
+	ret = haptics_set_vmax(h, h->vmax_mv);
+	if (ret)
+		return ret;
+
+	ret = haptics_configure_fifo_mmap(h);
+	if (ret)
+		return ret;
+
+	mutex_init(&h->play_lock);
+	mutex_init(&h->fifo_lock);
+	spin_lock_init(&h->play_queue_lock);
+	INIT_LIST_HEAD(&h->play_queue);
+	INIT_DELAYED_WORK(&h->play_work, haptics_play_work);
+	atomic_set(&h->gain, 0xFFFF);
+	h->active_effect_id = -1;
+
+	irq = platform_get_irq_byname(pdev, "fifo-empty");
+	if (irq < 0)
+		return dev_err_probe(h->dev, irq, "failed to get fifo-empty IRQ\n");
+
+	ret = devm_request_threaded_irq(h->dev, irq, NULL,
+					haptics_fifo_empty_irq,
+					IRQF_ONESHOT | IRQF_NO_AUTOEN,
+					"qcom-haptics-fifo-empty", h);
+	if (ret)
+		return dev_err_probe(h->dev, ret, "failed to request fifo-empty IRQ\n");
+
+	h->fifo_empty_irq = irq;
+	platform_set_drvdata(pdev, h);
+
+	pm_runtime_use_autosuspend(h->dev);
+	pm_runtime_set_autosuspend_delay(h->dev, HAPTICS_AUTOSUSPEND_MS);
+	ret = devm_pm_runtime_enable(h->dev);
+	if (ret)
+		return dev_err_probe(h->dev, ret, "enable runtime PM failed\n");
+
+	input = devm_input_allocate_device(h->dev);
+	if (!input)
+		return -ENOMEM;
+
+	input->name = "qcom-spmi-haptics";

Set bus type? BUS_HOST?

+	input_set_drvdata(input, h);
+	h->input = input;
+
+	input_set_capability(input, EV_FF, FF_CONSTANT);
+	input_set_capability(input, EV_FF, FF_PERIODIC);
+	input_set_capability(input, EV_FF, FF_CUSTOM);
+	input_set_capability(input, EV_FF, FF_GAIN);
+
+	ret = input_ff_create(input, HAPTICS_MAX_EFFECTS);
+	if (ret)
+		return ret;
+
+	ff = input->ff;
+	ff->upload   = haptics_upload_effect;
+	ff->playback = haptics_playback;
+	ff->erase    = haptics_erase;
+	ff->set_gain = haptics_set_gain;
+
+	ret = input_register_device(input);
+	if (ret) {
+		input_ff_destroy(input);

This is harmless but not needed: FF portion will be freed automatically.

+		return dev_err_probe(h->dev, ret, "failed to register input device\n");
+	}
+
+	return 0;
+}
+
+static void qcom_haptics_remove(struct platform_device *pdev)
+{
+	struct qcom_haptics *h = platform_get_drvdata(pdev);
+
+	/*
+	 * Unregister the input device explicitly at the beginning
+	 * to avoid the input device being used after the resources
+	 * are freed.
+	 */
+	input_unregister_device(h->input);
+	disable_delayed_work_sync(&h->play_work);
+	scoped_guard(mutex, &h->play_lock) {
+		haptics_queue_flush(h);
+		haptics_stop_locked(h, true);
+	}
+
+	haptics_enable_module(h, false);
+
+	scoped_guard(mutex, &h->fifo_lock) {
+		for (int i = 0; i < HAPTICS_MAX_EFFECTS; i++) {
+			kvfree(h->effects[i].fifo_data);
+			h->effects[i].fifo_data = NULL;
+		}
+	}

Most of this is better suited to close() method of input device.

+}
+
+static int qcom_haptics_runtime_suspend(struct device *dev)
+{
+	struct qcom_haptics *h = dev_get_drvdata(dev);
+
+	return haptics_enable_module(h, false);
+}
+
+static int qcom_haptics_runtime_resume(struct device *dev)
+{
+	struct qcom_haptics *h = dev_get_drvdata(dev);
+
+	return haptics_enable_module(h, true);
+}
+
+static int qcom_haptics_suspend(struct device *dev)
+{
+	struct qcom_haptics *h = dev_get_drvdata(dev);
+	int ret;
+
+	disable_delayed_work_sync(&h->play_work);
+	scoped_guard(mutex, &h->play_lock) {
+		haptics_queue_flush(h);
+		haptics_stop_locked(h, true);
+	}
+
+	ret = pm_runtime_force_suspend(dev);
+	if (ret)
+		enable_delayed_work(&h->play_work);
+
+	return ret;
+}
+
+static int qcom_haptics_resume(struct device *dev)
+{
+	struct qcom_haptics *h = dev_get_drvdata(dev);
+
+	enable_delayed_work(&h->play_work);
+
+	return pm_runtime_force_resume(dev);
+}
+
+static const struct dev_pm_ops qcom_haptics_pm_ops = {
+	SYSTEM_SLEEP_PM_OPS(qcom_haptics_suspend, qcom_haptics_resume)
+	RUNTIME_PM_OPS(qcom_haptics_runtime_suspend, qcom_haptics_runtime_resume,
+		       NULL)
+};
+
+static const struct of_device_id qcom_haptics_of_match[] = {
+	{ .compatible = "qcom,spmi-haptics" },
+	{}

	{ }

+};
+MODULE_DEVICE_TABLE(of, qcom_haptics_of_match);
+
+static struct platform_driver qcom_haptics_driver = {
+	.probe  = qcom_haptics_probe,
+	.remove = qcom_haptics_remove,
+	.driver = {
+		.name		= "qcom-spmi-haptics",
+		.of_match_table	= qcom_haptics_of_match,
+		.pm		= pm_ptr(&qcom_haptics_pm_ops),
+	},
+};
+module_platform_driver(qcom_haptics_driver);
+
+MODULE_DESCRIPTION("Qualcomm SPMI PMIC Haptics driver");
+MODULE_LICENSE("GPL");

Thanks.

-- 
Dmitry