linux-kernel - [PATCH v2 2/4] dma: gpi: Add Lock and Unlock TRE support to access SE exclusively

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Message-Id: <20240906191438.4104329-3-quic_msavaliy@quicinc.com>
Date: Sat,  7 Sep 2024 00:44:36 +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
Cc: quic_vdadhani@...cinc.com,
        Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
Subject: [PATCH v2 2/4] dma: gpi: Add Lock and Unlock TRE support to access SE exclusively

GSI DMA provides specific TREs namely Lock and Unlock TRE, which
provides mutual exclusive access to SE from any of the subsystem
(E.g. Apps, TZ, ADSP etc). Lock prevents other subsystems from
concurrently performing DMA transfers and avoids disturbance to
data path. Basically lock the SE for particular subsystem, 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.

TRE = Tranfser Ring Element, refers to the queued descriptor.

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 e6ebd688d746..ba11b2641ab6 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_I2C_LOCK		BIT(0)
+#define TRE_MINOR_TYPE		GENMASK(19, 16)
+#define TRE_MAJOR_TYPE		GENMASK(23, 20)
+
+/* Unlock TRE */
+#define TRE_I2C_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_I2C_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_I2C_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