HID: Intel-thc-hid: Intel-thc: Introduce interrupt delay control

This patch adds support for a new feature, named "Interrupt Delay",
allowing driver to set a specific delay time for next interrupt
detection. It gives driver a capability to control THC waiting time for
the next interrupt, to reduce the likelihood of spurious readings.

APIs added:
- thc_i2c_set_rx_int_delay(): Set I2C Rx input interrupt delay value
- thc_i2c_rx_int_delay_enable(): Enable or disable I2C Rx interrupt delay

As this interrupt delay feature is only applicable to RxDMA and must
remain disabled during SWDMA operations, it also involves a change
in SWDMA code to record the max input size control feature state
before SWDMA and restore the state after SWDMA.

Signed-off-by: Even Xu <even.xu@intel.com>
Tested-by: Chong Han <chong.han@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

Documentation/hid/intel-thc-hid.rst

@@ -202,6 +202,19 @@ input packet size with the given max size:
 This feature is used to avoid data corruption which will cause RxDMA buffer overrun issue for
 I2C bus, and enhance whole system stability.
 
+2.4 Interrupt delay
+-------------------
+
+Because of MCU performance limitation, some touch devices cannot de-assert interrupt pin
+immediately after input data is transferred, which cause an interrupt toggle delay. But THC
+always detects next interrupt immediately after last input interrupt is handled. In this
+case, the delayed interrupt de-assertion will be recognized as a new interrupt signal by THC,
+and causes THC to start an input report reading spuriously.
+
+In order to avoid this situation, THC introduced interrupt delay new feature in Panther Lake
+platform, where THC allows driver to set an interrupt delay. After this feature is enabled,
+THC will delay this given time for next interrupt detection.
+
 3. High level concept
 =====================
 

drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.c

@@ -2,6 +2,7 @@
 /* Copyright (c) 2024 Intel Corporation */
 
 #include <linux/bitfield.h>
+#include <linux/math.h>
 #include <linux/regmap.h>
 
 #include "intel-thc-dev.h"
@@ -1640,6 +1641,76 @@ int thc_i2c_rx_max_size_enable(struct thc_device *dev, bool enable)
 }
 EXPORT_SYMBOL_NS_GPL(thc_i2c_rx_max_size_enable, "INTEL_THC");
 
+/**
+ * thc_i2c_set_rx_int_delay - Set I2C Rx input interrupt delay value
+ * @dev: The pointer of THC private device context
+ * @delay_us: Interrupt delay value, unit is us
+ *
+ * Set @delay_us for I2C RxDMA input interrupt delay feature.
+ *
+ * Return: 0 on success, other error codes on failure.
+ */
+int thc_i2c_set_rx_int_delay(struct thc_device *dev, u32 delay_us)
+{
+	u32 val;
+	int ret;
+
+	if (!dev)
+		return -EINVAL;
+
+	if (!delay_us)
+		return -EOPNOTSUPP;
+
+	ret = regmap_read(dev->thc_regmap, THC_M_PRT_SW_SEQ_STS_OFFSET, &val);
+	if (ret)
+		return ret;
+
+	/* THC hardware counts at 10us unit */
+	val |= FIELD_PREP(THC_M_PRT_SPI_ICRRD_OPCODE_I2C_INTERVAL, DIV_ROUND_UP(delay_us, 10));
+
+	ret = regmap_write(dev->thc_regmap, THC_M_PRT_SPI_ICRRD_OPCODE_OFFSET, val);
+	if (ret)
+		return ret;
+
+	dev->i2c_int_delay_us = delay_us;
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(thc_i2c_set_rx_int_delay, "INTEL_THC");
+
+/**
+ * thc_i2c_rx_int_delay_enable - Enable I2C Rx interrupt delay
+ * @dev: The pointer of THC private device context
+ * @enable: Enable interrupt delay or not
+ *
+ * Enable or disable I2C RxDMA input interrupt delay feature.
+ * Input interrupt delay can only be enabled after interrupt delay value
+ * was set by thc_i2c_set_rx_int_delay().
+ *
+ * Return: 0 on success, other error codes on failure.
+ */
+int thc_i2c_rx_int_delay_enable(struct thc_device *dev, bool enable)
+{
+	u32 mask = THC_M_PRT_SPI_ICRRD_OPCODE_I2C_INTERVAL_EN;
+	u32 val = enable ? mask : 0;
+	int ret;
+
+	if (!dev)
+		return -EINVAL;
+
+	if (!dev->i2c_int_delay_us)
+		return -EOPNOTSUPP;
+
+	ret = regmap_write_bits(dev->thc_regmap, THC_M_PRT_SPI_ICRRD_OPCODE_OFFSET, mask, val);
+	if (ret)
+		return ret;
+
+	dev->i2c_int_delay_en = enable;
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(thc_i2c_rx_int_delay_enable, "INTEL_THC");
+
 MODULE_AUTHOR("Xinpeng Sun <xinpeng.sun@intel.com>");
 MODULE_AUTHOR("Even Xu <even.xu@intel.com>");
 

drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.h

@@ -63,7 +63,9 @@ enum thc_int_type {
  * @perf_limit: The delay between read operation and write operation
  * @i2c_subip_regs: The copy of THC I2C sub-system registers for resuming restore
  * @i2c_max_rx_size: I2C Rx transfer max input size
+ * @i2c_int_delay_us: I2C input interrupt delay, unit is us
  * @i2c_max_rx_size_en: Bool value that indicates I2C max input size control enabled or not
+ * @i2c_int_delay_en: Bool value that indicates I2C input interrupt delay enabled or not
  */
 struct thc_device {
 	struct device *dev;
@@ -85,7 +87,9 @@ struct thc_device {
 	u32 *i2c_subip_regs;
 
 	u32 i2c_max_rx_size;
+	u32 i2c_int_delay_us;
 	bool i2c_max_rx_size_en;
+	bool i2c_int_delay_en;
 };
 
 struct thc_device *thc_dev_init(struct device *device, void __iomem *mem_addr);
@@ -119,5 +123,7 @@ int thc_i2c_subip_regs_save(struct thc_device *dev);
 int thc_i2c_subip_regs_restore(struct thc_device *dev);
 int thc_i2c_set_rx_max_size(struct thc_device *dev, u32 max_rx_size);
 int thc_i2c_rx_max_size_enable(struct thc_device *dev, bool enable);
+int thc_i2c_set_rx_int_delay(struct thc_device *dev, u32 delay_us);
+int thc_i2c_rx_int_delay_enable(struct thc_device *dev, bool enable);
 
 #endif /* _INTEL_THC_DEV_H_ */

drivers/hid/intel-thc-hid/intel-thc/intel-thc-dma.c

@@ -725,6 +725,15 @@ static int thc_swdma_read_start(struct thc_device *dev, void *write_buff,
 		dev->dma_ctx->rx_max_size_en = true;
 	}
 
+	/*
+	 * Interrupt delay feature is in the same situation with max input size control feature,
+	 * needs record feature state before SWDMA.
+	 */
+	if (dev->i2c_int_delay_en) {
+		thc_i2c_rx_int_delay_enable(dev, false);
+		dev->dma_ctx->rx_int_delay_en = true;
+	}
+
 	mask = THC_M_PRT_RPRD_CNTRL_SW_THC_SWDMA_I2C_WBC |
 	       THC_M_PRT_RPRD_CNTRL_SW_THC_SWDMA_I2C_RX_DLEN_EN;
 	val = FIELD_PREP(THC_M_PRT_RPRD_CNTRL_SW_THC_SWDMA_I2C_WBC, write_len) |
@@ -776,6 +785,15 @@ static int thc_swdma_read_completion(struct thc_device *dev)
 		dev->dma_ctx->rx_max_size_en = false;
 	}
 
+	/*
+	 * Restore input interrupt delay feature to previous state after SWDMA if it was
+	 * enabled before SWDMA, and reset temp rx_int_delay_en variable for next time.
+	 */
+	if (dev->dma_ctx->rx_int_delay_en) {
+		thc_i2c_rx_int_delay_enable(dev, true);
+		dev->dma_ctx->rx_int_delay_en = false;
+	}
+
 	thc_reset_dma_settings(dev);
 
 	dma_set_start_bit(dev, &dev->dma_ctx->dma_config[THC_RXDMA2]);

drivers/hid/intel-thc-hid/intel-thc/intel-thc-dma.h

@@ -123,12 +123,15 @@ struct thc_dma_configuration {
  * @use_write_interrupts: Indicate TxDMA using interrupt or polling
  * @rx_max_size_en: Temp flag to indicate THC I2C Rx max input size control feature
  *                  enabled or not, only be used during SWDMA operation.
+ * @rx_int_delay_en: Temp flag to indicate THC I2C Rx interrupt delay feature
+ *                   enabled or not, only be used during SWDMA operation.
  */
 struct thc_dma_context {
 	struct thc_dma_configuration dma_config[MAX_THC_DMA_CHANNEL];
 	u8 use_write_interrupts;
 
 	bool rx_max_size_en;
+	bool rx_int_delay_en;
 };
 
 struct thc_device;

drivers/hid/intel-thc-hid/intel-thc/intel-thc-hw.h

@@ -400,6 +400,8 @@
 #define THC_M_PRT_SPI_ICRRD_OPCODE_SPI_QIO	GENMASK(15, 8)
 
 #define THC_M_PRT_SPI_ICRRD_OPCODE_I2C_MAX_SIZE		GENMASK(15, 0)
+#define THC_M_PRT_SPI_ICRRD_OPCODE_I2C_INTERVAL		GENMASK(23, 16)
+#define THC_M_PRT_SPI_ICRRD_OPCODE_I2C_INTERVAL_EN	BIT(30)
 #define THC_M_PRT_SPI_ICRRD_OPCODE_I2C_MAX_SIZE_EN	BIT(31)
 
 #define THC_M_PRT_INT_EN_SIPE				BIT(0)