linux-kernel - [PATCH v3 4/4] i2c: i2c-qcom-geni: Enable i2c controller sharing between two subsystems

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Message-Id: <20240927063108.2773304-5-quic_msavaliy@quicinc.com>
Date: Fri, 27 Sep 2024 12:01:08 +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: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
Subject: [PATCH v3 4/4] i2c: i2c-qcom-geni: Enable i2c controller sharing between two subsystems

Add support to share I2C SE by two Subsystems in a mutually exclusive way.
Use "qcom,shared-se" flag in a particular i2c instance node if the usecase
requires i2c controller to be shared.

Sharing of SE(Serial engine) is possible only for GSI mode as each
subsystem(SS) can queue transfers over its own GPII Channel. For non GSI
mode, we should force disable this feature even if set by user from DT by
mistake.

I2C driver just need to mark first_msg and last_msg flag to help indicate
GPI driver to take lock and unlock TRE there by protecting from concurrent
access from other EE or Subsystem.

gpi_create_i2c_tre() function at gpi.c will take care of adding Lock and
Unlock TRE for the respective transfer operations.

Since the GPIOs are also shared between two SS, do not unconfigure them
during runtime suspend. This will allow other SS to continue to transfer
the data without any disturbance over the IO lines.

Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
---
 drivers/i2c/busses/i2c-qcom-geni.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index 212336f724a6..479fa8e1c33f 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 // Copyright (c) 2017-2018, The Linux Foundation. All rights reserved.
+// Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
 
 #include <linux/acpi.h>
 #include <linux/clk.h>
@@ -602,6 +603,7 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
 	peripheral.clk_div = itr->clk_div;
 	peripheral.set_config = 1;
 	peripheral.multi_msg = false;
+	peripheral.shared_se = gi2c->se.shared_geni_se;
 
 	for (i = 0; i < num; i++) {
 		gi2c->cur = &msgs[i];
@@ -612,6 +614,8 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
 		if (i < num - 1)
 			peripheral.stretch = 1;
 
+		peripheral.first_msg = (i == 0);
+		peripheral.last_msg = (i == num - 1);
 		peripheral.addr = msgs[i].addr;
 
 		ret =  geni_i2c_gpi(gi2c, &msgs[i], &config,
@@ -631,8 +635,11 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
 		dma_async_issue_pending(gi2c->tx_c);
 
 		time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
-		if (!time_left)
+		if (!time_left) {
+			dev_dbg(gi2c->se.dev, "I2C timeout gpi flags:%d addr:0x%x\n",
+						gi2c->cur->flags, gi2c->cur->addr);
 			gi2c->err = -ETIMEDOUT;
+		}
 
 		if (gi2c->err) {
 			ret = gi2c->err;
@@ -800,6 +807,11 @@ static int geni_i2c_probe(struct platform_device *pdev)
 		gi2c->clk_freq_out = KHZ(100);
 	}
 
+	if (of_property_read_bool(pdev->dev.of_node, "qcom,shared-se")) {
+		gi2c->se.shared_geni_se = true;
+		dev_dbg(&pdev->dev, "I2C is shared between subsystems\n");
+	}
+
 	if (has_acpi_companion(dev))
 		ACPI_COMPANION_SET(&gi2c->adap.dev, ACPI_COMPANION(dev));
 
@@ -870,8 +882,10 @@ static int geni_i2c_probe(struct platform_device *pdev)
 	else
 		fifo_disable = readl_relaxed(gi2c->se.base + GENI_IF_DISABLE_RO) & FIFO_IF_DISABLE;
 
-	if (fifo_disable) {
-		/* FIFO is disabled, so we can only use GPI DMA */
+	if (fifo_disable || gi2c->se.shared_geni_se) {
+		/* FIFO is disabled, so we can only use GPI DMA.
+		 * SE can be shared in GSI mode between subsystems, each SS owns a GPII.
+		 **/
 		gi2c->gpi_mode = true;
 		ret = setup_gpi_dma(gi2c);
 		if (ret) {
@@ -883,6 +897,9 @@ static int geni_i2c_probe(struct platform_device *pdev)
 		dev_dbg(dev, "Using GPI DMA mode for I2C\n");
 	} else {
 		gi2c->gpi_mode = false;
+
+		/* Force disable shared SE case for non GSI mode */
+		gi2c->se.shared_geni_se = false;
 		tx_depth = geni_se_get_tx_fifo_depth(&gi2c->se);
 
 		/* I2C Master Hub Serial Elements doesn't have the HW_PARAM_0 register */
@@ -964,7 +981,6 @@ static int __maybe_unused geni_i2c_runtime_suspend(struct device *dev)
 	if (ret) {
 		enable_irq(gi2c->irq);
 		return ret;
-
 	} else {
 		gi2c->suspended = 1;
 	}
-- 
2.25.1