HID: Intel-thc-hid: Intel-thc: Introduce max input size control

This patch adds support for a new feature, named "Max Input Size
Control", allowing driver to set a maximum input size for RxDMA. This
enhancement aims to prevent RxDMA buffer overruns caused by data
corruption on the I2C bus, thereby improving overall system stability.

APIs added:
- thc_i2c_set_rx_max_size(): Set the maximum input size for I2C RxDMA.
- thc_i2c_rx_max_size_enable(): Enable or disable the max input size
  control.

As this max input size control 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

@@ -188,6 +188,20 @@ Control register.
 Reset line is controlled by BIOS (or EFI) through ACPI _RST method, driver needs to call this
 device ACPI _RST method to reset touch IC during initialization.
 
+2.3 Max input size control
+--------------------------
+
+This is a new feature introduced in Panther Lake platform, THC hardware allows driver to set
+a max input size for RxDMA. After this max size gets set and enabled, for every input report
+packet reading, THC hardware sequencer will first read incoming input packet size, then compare
+input packet size with the given max size:
+- if input packet size <= max size, THC continues using input packet size to finish the reading
+- if input packet size > max size, there is potential input data crash risk during
+  transferring, THC will use max size instead of input packet size for reading
+
+This feature is used to avoid data corruption which will cause RxDMA buffer overrun issue for
+I2C bus, and enhance whole system stability.
+
 3. High level concept
 =====================
 

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

@@ -1571,6 +1571,75 @@ int thc_i2c_subip_regs_restore(struct thc_device *dev)
 }
 EXPORT_SYMBOL_NS_GPL(thc_i2c_subip_regs_restore, "INTEL_THC");
 
+/**
+ * thc_i2c_set_rx_max_size - Set I2C Rx transfer max input size
+ * @dev: The pointer of THC private device context
+ * @max_rx_size: Max input report packet size for input report
+ *
+ * Set @max_rx_size for I2C RxDMA max input size control feature.
+ *
+ * Return: 0 on success, other error codes on failure.
+ */
+int thc_i2c_set_rx_max_size(struct thc_device *dev, u32 max_rx_size)
+{
+	u32 val;
+	int ret;
+
+	if (!dev)
+		return -EINVAL;
+
+	if (!max_rx_size)
+		return -EOPNOTSUPP;
+
+	ret = regmap_read(dev->thc_regmap, THC_M_PRT_SW_SEQ_STS_OFFSET, &val);
+	if (ret)
+		return ret;
+
+	val |= FIELD_PREP(THC_M_PRT_SPI_ICRRD_OPCODE_I2C_MAX_SIZE, max_rx_size);
+
+	ret = regmap_write(dev->thc_regmap, THC_M_PRT_SPI_ICRRD_OPCODE_OFFSET, val);
+	if (ret)
+		return ret;
+
+	dev->i2c_max_rx_size = max_rx_size;
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(thc_i2c_set_rx_max_size, "INTEL_THC");
+
+/**
+ * thc_i2c_rx_max_size_enable - Enable I2C Rx max input size control
+ * @dev: The pointer of THC private device context
+ * @enable: Enable max input size control or not
+ *
+ * Enable or disable I2C RxDMA max input size control feature.
+ * Max input size control only can be enabled after max input size
+ * was set by thc_i2c_set_rx_max_size().
+ *
+ * Return: 0 on success, other error codes on failure.
+ */
+int thc_i2c_rx_max_size_enable(struct thc_device *dev, bool enable)
+{
+	u32 mask = THC_M_PRT_SPI_ICRRD_OPCODE_I2C_MAX_SIZE_EN;
+	u32 val = enable ? mask : 0;
+	int ret;
+
+	if (!dev)
+		return -EINVAL;
+
+	if (!dev->i2c_max_rx_size)
+		return -EOPNOTSUPP;
+
+	ret = regmap_write_bits(dev->thc_regmap, THC_M_PRT_SPI_ICRRD_OPCODE_OFFSET, mask, val);
+	if (ret)
+		return ret;
+
+	dev->i2c_max_rx_size_en = enable;
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(thc_i2c_rx_max_size_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

@@ -62,6 +62,8 @@ enum thc_int_type {
  * @swdma_done: Bool value that indicates if SWDMA sequence is done
  * @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_max_rx_size_en: Bool value that indicates I2C max input size control enabled or not
  */
 struct thc_device {
 	struct device *dev;
@@ -81,6 +83,9 @@ struct thc_device {
 	u32 perf_limit;
 
 	u32 *i2c_subip_regs;
+
+	u32 i2c_max_rx_size;
+	bool i2c_max_rx_size_en;
 };
 
 struct thc_device *thc_dev_init(struct device *device, void __iomem *mem_addr);
@@ -112,5 +117,7 @@ int thc_i2c_subip_init(struct thc_device *dev, const u32 target_address,
 		       const u32 speed, const u32 hcnt, const u32 lcnt);
 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);
 
 #endif /* _INTEL_THC_DEV_H_ */

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

@@ -712,6 +712,19 @@ static int thc_swdma_read_start(struct thc_device *dev, void *write_buff,
 
 	thc_reset_dma_settings(dev);
 
+	/*
+	 * Max input size control feature is only available for RxDMA, it must keep disabled
+	 * during SWDMA operation, and restore to previous state after SWDMA is done.
+	 * Max input size variables in THC device context track hardware state, and keep change
+	 * when feature state was changed, so those variables cannot be used to record feature
+	 * state after state was changed during SWDMA operation. Here have to use a temp variable
+	 * in DMA context to record feature state before SWDMA operation.
+	 */
+	if (dev->i2c_max_rx_size_en) {
+		thc_i2c_rx_max_size_enable(dev, false);
+		dev->dma_ctx->rx_max_size_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) |
@@ -754,6 +767,15 @@ static int thc_swdma_read_completion(struct thc_device *dev)
 	if (ret)
 		return ret;
 
+	/*
+	 * Restore max input size control feature to previous state after SWDMA if it was
+	 * enabled before SWDMA, and reset temp rx_max_size_en variable for next time.
+	 */
+	if (dev->dma_ctx->rx_max_size_en) {
+		thc_i2c_rx_max_size_enable(dev, true);
+		dev->dma_ctx->rx_max_size_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

@@ -121,10 +121,14 @@ struct thc_dma_configuration {
  * struct thc_dma_context - THC DMA context
  * @thc_dma_configuration: Array of all THC Channel configures
  * @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.
  */
 struct thc_dma_context {
 	struct thc_dma_configuration dma_config[MAX_THC_DMA_CHANNEL];
 	u8 use_write_interrupts;
+
+	bool rx_max_size_en;
 };
 
 struct thc_device;

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

@@ -399,6 +399,9 @@
 #define THC_M_PRT_SPI_ICRRD_OPCODE_SPI_DIO	GENMASK(23, 16)
 #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_MAX_SIZE_EN	BIT(31)
+
 #define THC_M_PRT_INT_EN_SIPE				BIT(0)
 #define THC_M_PRT_INT_EN_SBO				BIT(1)
 #define THC_M_PRT_INT_EN_SIDR				BIT(2)