FROMLIST: dmaengine: qcom: gpi: Add lock/unlock TREs for multi-owner I2C transfers

Some platforms use a QUP-based I2C controller in a configuration where the
controller is shared with another system processor (described in DT using
qcom,qup-multi-owner). In such setups, GPI hardware lock/unlock TREs can be
used to serialize access to the controller.

Add support to emit lock and unlock TREs around I2C transfers and increase
the maximum TRE count to account for the additional elements.

Also simplify the client interface by replacing multiple boolean fields
(shared flag and message position tracking) with a single lock_action
selector (acquire/release/none), as the GPI driver only needs to know
whether to emit lock/unlock TREs for a given transfer.

Link: https://lore.kernel.org/all/20260331114742.2896317-3-mukesh.savaliya@oss.qualcomm.com/
Signed-off-by: Mukesh Kumar Savaliya <mukesh.savaliya@oss.qualcomm.com>

Author: mukesh-savaliya

drivers/dma/qcom/gpi.c

@@ -2,6 +2,7 @@
 /*
  * Copyright (c) 2017-2020, The Linux Foundation. All rights reserved.
  * Copyright (c) 2020, Linaro Limited
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
  */
 
 #include <dt-bindings/dma/qcom-gpi.h>
@@ -67,6 +68,14 @@
 #define TRE_DMA_LEN		GENMASK(23, 0)
 #define TRE_DMA_IMMEDIATE_LEN	GENMASK(3, 0)
 
+/* Lock TRE */
+#define TRE_LOCK		BIT(0)
+#define TRE_MINOR_TYPE		GENMASK(19, 16)
+#define TRE_MAJOR_TYPE		GENMASK(23, 20)
+
+/* Unlock TRE */
+#define TRE_UNLOCK		BIT(8)
+
 /* Register offsets from gpi-top */
 #define GPII_n_CH_k_CNTXT_0_OFFS(n, k)	(0x20000 + (0x4000 * (n)) + (0x80 * (k)))
 #define GPII_n_CH_k_CNTXT_0_EL_SIZE	GENMASK(31, 24)
@@ -518,7 +527,7 @@ struct gpii {
 	bool ieob_set;
 };
 
-#define MAX_TRE 3
+#define MAX_TRE 5
 
 struct gpi_desc {
 	struct virt_dma_desc vd;
@@ -1625,12 +1634,27 @@ static int gpi_create_i2c_tre(struct gchan *chan, struct gpi_desc *desc,
 			      unsigned long flags)
 {
 	struct gpi_i2c_config *i2c = chan->config;
+	enum gpi_lock_action lock_action = i2c->lock_action;
 	struct device *dev = chan->gpii->gpi_dev->dev;
 	unsigned int tre_idx = 0;
 	dma_addr_t address;
 	struct gpi_tre *tre;
 	unsigned int i;
 
+	/* Optional lock TRE before transfer */
+	if (lock_action == GPI_LOCK_ACQUIRE) {
+		tre = &desc->tre[tre_idx];
+		tre_idx++;
+
+		tre->dword[0] = 0;
+		tre->dword[1] = 0;
+		tre->dword[2] = 0;
+		tre->dword[3] = u32_encode_bits(1, TRE_LOCK);
+		tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_IEOB);
+		tre->dword[3] |= u32_encode_bits(0, TRE_MINOR_TYPE);
+		tre->dword[3] |= u32_encode_bits(3, TRE_MAJOR_TYPE);
+	}
+
 	/* first create config tre if applicable */
 	if (i2c->set_config) {
 		tre = &desc->tre[tre_idx];
@@ -1690,6 +1714,24 @@ static int gpi_create_i2c_tre(struct gchan *chan, struct gpi_desc *desc,
 
 		if (!(flags & DMA_PREP_INTERRUPT))
 			tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_BEI);
+
+		/* If multi-owner and this is the release boundary, chain it */
+		if (i2c->lock_action == GPI_LOCK_RELEASE)
+			tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_CHAIN);
+	}
+
+	/* Optional unlock TRE after transfer */
+	if (lock_action == GPI_LOCK_RELEASE && i2c->op != I2C_READ) {
+		tre = &desc->tre[tre_idx];
+		tre_idx++;
+
+		tre->dword[0] = 0;
+		tre->dword[1] = 0;
+		tre->dword[2] = 0;
+		tre->dword[3] = u32_encode_bits(1, TRE_UNLOCK);
+		tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_IEOB);
+		tre->dword[3] |= u32_encode_bits(1, TRE_MINOR_TYPE);
+		tre->dword[3] |= u32_encode_bits(3, TRE_MAJOR_TYPE);
 	}
 
 	for (i = 0; i < tre_idx; i++)

include/linux/dma/qcom-gpi-dma.h

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Copyright (c) 2020, Linaro Limited
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
  */
 
 #ifndef QCOM_GPI_DMA_H
@@ -54,6 +55,21 @@ enum i2c_op {
 	I2C_READ,
 };
 
+/**
+ * enum gpi_lock_action - request lock/unlock TRE sequencing
+ * @GPI_LOCK_NONE: No lock/unlock TRE requested for this transfer
+ * @GPI_LOCK_ACQUIRE: Emit a lock TRE before the transfer
+ * @GPI_LOCK_RELEASE: Emit an unlock TRE after the transfer
+ *
+ * Used by protocol drivers for multi-owner controller setups (e.g. when
+ * DeviceTree indicates the controller is shared via qcom,qup-multi-owner).
+ */
+enum gpi_lock_action {
+	GPI_LOCK_NONE = 0,
+	GPI_LOCK_ACQUIRE,
+	GPI_LOCK_RELEASE,
+};
+
 /**
  * struct gpi_i2c_config - i2c config for peripheral
  *
@@ -67,7 +83,8 @@ enum i2c_op {
  * @set_config: set peripheral config
  * @rx_len: receive length for buffer
  * @op: i2c cmd
- * @multi_msg: is part of multi i2c r-w msgs
+ * @muli-msg: is part of multi i2c r-w msgs
+ * @lock_action: request lock/unlock TRE sequencing for this transfer
  */
 struct gpi_i2c_config {
 	u8 set_config;
@@ -81,6 +98,7 @@ struct gpi_i2c_config {
 	u32 rx_len;
 	enum i2c_op op;
 	bool multi_msg;
+	enum gpi_lock_action lock_action;
 };
 
 #endif /* QCOM_GPI_DMA_H */