[PATCH V2 2/2] i2c: i2c-qcom-geni: Add shutdown callback for i2c

[Roja Rani Yarubandi]

If the hardware is still accessing memory after SMMU translation
is disabled (as part of smmu shutdown callback), then the
IOVAs (I/O virtual address) which it was using will go on the bus
as the physical addresses which will result in unknown crashes
like NoC/interconnect errors.

So, implement shutdown callback to i2c driver to unmap DMA mappings
during system "reboot" or "shutdown".

Signed-off-by: Roja Rani Yarubandi <rojay at codeaurora.org>
---
Changes in V2:
 - As per Stephen's comments added seperate function for stop transfer,
   fixed minor nitpicks.

 drivers/i2c/busses/i2c-qcom-geni.c | 43 ++++++++++++++++++++++++++++++
 include/linux/qcom-geni-se.h       |  5 ++++
 2 files changed, 48 insertions(+)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index 1fda5c7c2cfc..d07f2f33bb75 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -486,6 +486,28 @@ static int geni_i2c_xfer(struct i2c_adapter *adap,
 	return ret;
 }
 
+static void geni_i2c_stop_xfer(struct geni_i2c_dev *gi2c)
+{
+	u32 val;
+	struct geni_se *se = &gi2c->se;
+
+	val = readl_relaxed(gi2c->se.base + SE_DMA_DEBUG_REG0);
+	if (val & DMA_TX_ACTIVE) {
+		geni_i2c_abort_xfer(gi2c);
+		gi2c->cur_wr = 0;
+		if (gi2c->err)
+			geni_i2c_tx_fsm_rst(gi2c);
+		geni_se_tx_dma_unprep(se, gi2c->tx_dma, gi2c->xfer_len);
+	}
+	if (val & DMA_RX_ACTIVE) {
+		geni_i2c_abort_xfer(gi2c);
+		gi2c->cur_rd = 0;
+		if (gi2c->err)
+			geni_i2c_rx_fsm_rst(gi2c);
+		geni_se_rx_dma_unprep(se, gi2c->rx_dma, gi2c->xfer_len);
+	}
+}
+
 static u32 geni_i2c_func(struct i2c_adapter *adap)
 {
 	return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
@@ -617,6 +639,26 @@ static int geni_i2c_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static void geni_i2c_shutdown(struct platform_device *pdev)
+{
+	int ret;
+	u32 dma;
+	struct geni_i2c_dev *gi2c = platform_get_drvdata(pdev);
+	struct geni_se *se = &gi2c->se;
+
+	ret = pm_runtime_get_sync(gi2c->se.dev);
+	if (ret < 0) {
+		dev_err(gi2c->se.dev, "Failed to resume device: %d\n", ret);
+		return;
+	}
+
+	dma = readl_relaxed(se->base + SE_GENI_DMA_MODE_EN);
+	if (dma)
+		geni_i2c_stop_xfer(gi2c);
+
+	pm_runtime_put_sync_suspend(gi2c->se.dev);
+}
+
 static int __maybe_unused geni_i2c_runtime_suspend(struct device *dev)
 {
 	int ret;
@@ -677,6 +719,7 @@ MODULE_DEVICE_TABLE(of, geni_i2c_dt_match);
 static struct platform_driver geni_i2c_driver = {
 	.probe  = geni_i2c_probe,
 	.remove = geni_i2c_remove,
+	.shutdown = geni_i2c_shutdown,
 	.driver = {
 		.name = "geni_i2c",
 		.pm = &geni_i2c_pm_ops,
diff --git a/include/linux/qcom-geni-se.h b/include/linux/qcom-geni-se.h
index dd464943f717..c3c016496d98 100644
--- a/include/linux/qcom-geni-se.h
+++ b/include/linux/qcom-geni-se.h
@@ -77,6 +77,7 @@ struct geni_se {
 #define SE_DMA_RX_FSM_RST		0xd58
 #define SE_HW_PARAM_0			0xe24
 #define SE_HW_PARAM_1			0xe28
+#define SE_DMA_DEBUG_REG0		0xe40
 
 /* GENI_FORCE_DEFAULT_REG fields */
 #define FORCE_DEFAULT	BIT(0)
@@ -207,6 +208,10 @@ struct geni_se {
 #define RX_GENI_CANCEL_IRQ		BIT(11)
 #define RX_GENI_GP_IRQ_EXT		GENMASK(13, 12)
 
+/* SE_DMA_DEBUG_REG0 Register fields */
+#define DMA_TX_ACTIVE			BIT(0)
+#define DMA_RX_ACTIVE			BIT(1)
+
 /* SE_HW_PARAM_0 fields */
 #define TX_FIFO_WIDTH_MSK		GENMASK(29, 24)
 #define TX_FIFO_WIDTH_SHFT		24
-- 
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