linux-kernel - [PATCH v5 2/4] dmaengine: gpi: Add Lock and Unlock TRE support to access I2C exclusively

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Message-Id: <20241129144357.2008465-3-quic_msavaliy@quicinc.com>
Date: Fri, 29 Nov 2024 20:13:55 +0530
From: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
To: konrad.dybcio@...aro.org, andersson@...nel.org, andi.shyti@...nel.org,
        linux-arm-msm@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        conor+dt@...nel.org, agross@...nel.org, devicetree@...r.kernel.org,
        vkoul@...nel.org, linux@...blig.org, dan.carpenter@...aro.org,
        Frank.Li@....com, konradybcio@...nel.org, bryan.odonoghue@...aro.org,
        krzk+dt@...nel.org, robh@...nel.org
Cc: quic_vdadhani@...cinc.com,
        Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
Subject: [PATCH v5 2/4] dmaengine: gpi: Add Lock and Unlock TRE support to access I2C exclusively

GSI DMA provides specific TREs(Transfer ring element) namely Lock and
Unlock TRE. It provides mutually exclusive access to I2C controller from
any of the processor(Apps,ADSP). Lock prevents other subsystems from
concurrently performing DMA transfers and avoids disturbance to data path.
Basically for shared I2C usecase, lock the SE(Serial Engine) for one of
the processor, complete the transfer, unlock the SE.

Apply Lock TRE for the first transfer of shared SE and Apply Unlock
TRE for the last transfer.

Also change MAX_TRE macro to 5 from 3 because of the two additional TREs.

Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
---
 drivers/dma/qcom/gpi.c           | 37 +++++++++++++++++++++++++++++++-
 include/linux/dma/qcom-gpi-dma.h |  6 ++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c
index 52a7c8f2498f..c74417240012 100644
--- a/drivers/dma/qcom/gpi.c
+++ b/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) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
  */
 
 #include <dt-bindings/dma/qcom-gpi.h>
@@ -65,6 +66,14 @@
 /* DMA TRE */
 #define TRE_DMA_LEN		GENMASK(23, 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)
@@ -516,7 +525,7 @@ struct gpii {
 	bool ieob_set;
 };
 
-#define MAX_TRE 3
+#define MAX_TRE 5
 
 struct gpi_desc {
 	struct virt_dma_desc vd;
@@ -1637,6 +1646,19 @@ static int gpi_create_i2c_tre(struct gchan *chan, struct gpi_desc *desc,
 	struct gpi_tre *tre;
 	unsigned int i;
 
+	/* create lock tre for first tranfser */
+	if (i2c->shared_se && i2c->first_msg) {
+		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(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];
@@ -1695,6 +1717,19 @@ static int gpi_create_i2c_tre(struct gchan *chan, struct gpi_desc *desc,
 		tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_IEOT);
 	}
 
+	/* Unlock tre for last transfer */
+	if (i2c->shared_se && i2c->last_msg && 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_MINOR_TYPE);
+		tre->dword[3] |= u32_encode_bits(3, TRE_MAJOR_TYPE);
+	}
+
 	for (i = 0; i < tre_idx; i++)
 		dev_dbg(dev, "TRE:%d %x:%x:%x:%x\n", i, desc->tre[i].dword[0],
 			desc->tre[i].dword[1], desc->tre[i].dword[2], desc->tre[i].dword[3]);
diff --git a/include/linux/dma/qcom-gpi-dma.h b/include/linux/dma/qcom-gpi-dma.h
index 6680dd1a43c6..8589c711afae 100644
--- a/include/linux/dma/qcom-gpi-dma.h
+++ b/include/linux/dma/qcom-gpi-dma.h
@@ -65,6 +65,9 @@ enum i2c_op {
  * @rx_len: receive length for buffer
  * @op: i2c cmd
  * @muli-msg: is part of multi i2c r-w msgs
+ * @shared_se: bus is shared between subsystems
+ * @bool first_msg: use it for tracking multimessage xfer
+ * @bool last_msg: use it for tracking multimessage xfer
  */
 struct gpi_i2c_config {
 	u8 set_config;
@@ -78,6 +81,9 @@ struct gpi_i2c_config {
 	u32 rx_len;
 	enum i2c_op op;
 	bool multi_msg;
+	bool shared_se;
+	bool first_msg;
+	bool last_msg;
 };
 
 #endif /* QCOM_GPI_DMA_H */
-- 
2.25.1