[PATCH V4] 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 stop on-going transfer
and unmap DMA mappings during system "reboot" or "shutdown".

Store DMA mapping data in geni_i2c_dev struct to enhance DMA mapping
data scope. For example during shutdown callback to unmap DMA mapping,
this stored DMA mapping data can be used to call geni_se_tx_dma_unprep,
geni_se_rx_dma_unprep and  i2c_put_dma_safe_msg_buf functions.

Add two helper functions geni_i2c_rx_msg_cleanup and
geni_i2c_tx_msg_cleanup to unwrap the things after rx/tx FIFO/DMA
transfers, so that the same can be used in geni_i2c_stop_xfer()
function during shutdown callback.

Remove "iova" check from geni_se_tx_dma_unprep and geni_se_rx_dma_unprep
fucntions as invalidating with dma_mapping_error() is enough.

Fixes: 37692de5d523 ("i2c: i2c-qcom-geni: Add bus driver for the Qualcomm GENI I2C controller")
Signed-off-by: Roja Rani Yarubandi <rojay@xxxxxxxxxxxxxx>
---
Changes in V2:
 - As per Stephen's comments added seperate function for stop transfer,
   fixed minor nitpicks.
 - As per Stephen's comments, changed commit text.

Changes in V3:
 - As per Stephen's comments, squashed patch 1 into patch 2, added Fixes tag.
 - As per Akash's comments, included FIFO case in stop_xfer, fixed minor nitpicks.

Changes in V4:
 - As per Stephen's comments cleaned up geni_i2c_stop_xfer function,
   added dma_buf in geni_i2c_dev struct to call i2c_put_dma_safe_msg_buf()
   from other functions, removed "iova" check in geni_se_rx_dma_unprep()
   and geni_se_tx_dma_unprep() functions.
 - Added two helper functions geni_i2c_rx_msg_cleanup() and
   geni_i2c_tx_msg_cleanup() to unwrap the things after rx/tx FIFO/DMA
   transfers, so that the same can be used in geni_i2c_stop_xfer() function
   during shutdown callback. Updated commit text accordingly.
 - In stop_xfer check whether it is tx/rx transfer using I2C_M_RD which is valid
   for both FIFO and DMA cases, so dropped DMA_RX_ACTIVE and DMA_TX_ACTIVE bit
   check of SE_DMA_DEBUG_REG0 register.

 drivers/i2c/busses/i2c-qcom-geni.c | 93 ++++++++++++++++++++++++------
 drivers/soc/qcom/qcom-geni-se.c    |  4 +-
 2 files changed, 78 insertions(+), 19 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index dead5db3315a..b0d8043c8cb2 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -86,6 +86,10 @@ struct geni_i2c_dev {
 	u32 clk_freq_out;
 	const struct geni_i2c_clk_fld *clk_fld;
 	int suspended;
+	void *dma_buf;
+	size_t xfer_len;
+	dma_addr_t tx_dma;
+	dma_addr_t rx_dma;
 };
 
 struct geni_i2c_err_log {
@@ -307,7 +311,6 @@ static void geni_i2c_abort_xfer(struct geni_i2c_dev *gi2c)
 
 	spin_lock_irqsave(&gi2c->lock, flags);
 	geni_i2c_err(gi2c, GENI_TIMEOUT);
-	gi2c->cur = NULL;
 	geni_se_abort_m_cmd(&gi2c->se);
 	spin_unlock_irqrestore(&gi2c->lock, flags);
 	do {
@@ -349,10 +352,62 @@ static void geni_i2c_tx_fsm_rst(struct geni_i2c_dev *gi2c)
 		dev_err(gi2c->se.dev, "Timeout resetting TX_FSM\n");
 }
 
+static void geni_i2c_rx_msg_cleanup(struct geni_i2c_dev *gi2c)
+{
+	struct geni_se *se = &gi2c->se;
+
+	gi2c->cur_rd = 0;
+	if (gi2c->dma_buf) {
+		if (gi2c->err)
+			geni_i2c_rx_fsm_rst(gi2c);
+		geni_se_rx_dma_unprep(se, gi2c->rx_dma, gi2c->xfer_len);
+		i2c_put_dma_safe_msg_buf(gi2c->dma_buf, gi2c->cur, !gi2c->err);
+	}
+}
+
+static void geni_i2c_tx_msg_cleanup(struct geni_i2c_dev *gi2c)
+{
+	struct geni_se *se = &gi2c->se;
+
+	gi2c->cur_wr = 0;
+	if (gi2c->dma_buf) {
+		if (gi2c->err)
+			geni_i2c_tx_fsm_rst(gi2c);
+		geni_se_tx_dma_unprep(se, gi2c->tx_dma, gi2c->xfer_len);
+		i2c_put_dma_safe_msg_buf(gi2c->dma_buf, gi2c->cur, !gi2c->err);
+	}
+}
+
+static void geni_i2c_stop_xfer(struct geni_i2c_dev *gi2c)
+{
+	int ret;
+	u32 geni_status;
+
+	/* Resume device, as runtime suspend can happen anytime during transfer */
+	ret = pm_runtime_get_sync(gi2c->se.dev);
+	if (ret < 0) {
+		dev_err(gi2c->se.dev, "Failed to resume device: %d\n", ret);
+		return;
+	}
+
+	geni_status = readl_relaxed(gi2c->se.base + SE_GENI_STATUS);
+	if (!(geni_status & M_GENI_CMD_ACTIVE))
+		goto out;
+
+	geni_i2c_abort_xfer(gi2c);
+	if (gi2c->cur->flags & I2C_M_RD)
+		geni_i2c_rx_msg_cleanup(gi2c);
+	else
+		geni_i2c_tx_msg_cleanup(gi2c);
+	gi2c->cur = NULL;
+out:
+	pm_runtime_put_sync_suspend(gi2c->se.dev);
+}
+
 static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 				u32 m_param)
 {
-	dma_addr_t rx_dma;
+	dma_addr_t rx_dma = 0;
 	unsigned long time_left;
 	void *dma_buf = NULL;
 	struct geni_se *se = &gi2c->se;
@@ -372,6 +427,10 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 		geni_se_select_mode(se, GENI_SE_FIFO);
 		i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
 		dma_buf = NULL;
+	} else {
+		gi2c->xfer_len = len;
+		gi2c->rx_dma = rx_dma;
+		gi2c->dma_buf = dma_buf;
 	}
 
 	geni_se_setup_m_cmd(se, I2C_READ, m_param);
@@ -380,13 +439,7 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 	if (!time_left)
 		geni_i2c_abort_xfer(gi2c);
 
-	gi2c->cur_rd = 0;
-	if (dma_buf) {
-		if (gi2c->err)
-			geni_i2c_rx_fsm_rst(gi2c);
-		geni_se_rx_dma_unprep(se, rx_dma, len);
-		i2c_put_dma_safe_msg_buf(dma_buf, msg, !gi2c->err);
-	}
+	geni_i2c_rx_msg_cleanup(gi2c);
 
 	return gi2c->err;
 }
@@ -394,7 +447,7 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 				u32 m_param)
 {
-	dma_addr_t tx_dma;
+	dma_addr_t tx_dma = 0;
 	unsigned long time_left;
 	void *dma_buf = NULL;
 	struct geni_se *se = &gi2c->se;
@@ -414,6 +467,10 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 		geni_se_select_mode(se, GENI_SE_FIFO);
 		i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
 		dma_buf = NULL;
+	} else {
+		gi2c->xfer_len = len;
+		gi2c->tx_dma = tx_dma;
+		gi2c->dma_buf = dma_buf;
 	}
 
 	geni_se_setup_m_cmd(se, I2C_WRITE, m_param);
@@ -425,13 +482,7 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 	if (!time_left)
 		geni_i2c_abort_xfer(gi2c);
 
-	gi2c->cur_wr = 0;
-	if (dma_buf) {
-		if (gi2c->err)
-			geni_i2c_tx_fsm_rst(gi2c);
-		geni_se_tx_dma_unprep(se, tx_dma, len);
-		i2c_put_dma_safe_msg_buf(dma_buf, msg, !gi2c->err);
-	}
+	geni_i2c_tx_msg_cleanup(gi2c);
 
 	return gi2c->err;
 }
@@ -630,6 +681,13 @@ static int geni_i2c_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static void geni_i2c_shutdown(struct platform_device *pdev)
+{
+	struct geni_i2c_dev *gi2c = platform_get_drvdata(pdev);
+
+	geni_i2c_stop_xfer(gi2c);
+}
+
 static int __maybe_unused geni_i2c_runtime_suspend(struct device *dev)
 {
 	int ret;
@@ -694,6 +752,7 @@ 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/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c
index d0e4f520cff8..0216b38c1e9a 100644
--- a/drivers/soc/qcom/qcom-geni-se.c
+++ b/drivers/soc/qcom/qcom-geni-se.c
@@ -705,7 +705,7 @@ void geni_se_tx_dma_unprep(struct geni_se *se, dma_addr_t iova, size_t len)
 {
 	struct geni_wrapper *wrapper = se->wrapper;
 
-	if (iova && !dma_mapping_error(wrapper->dev, iova))
+	if (!dma_mapping_error(wrapper->dev, iova))
 		dma_unmap_single(wrapper->dev, iova, len, DMA_TO_DEVICE);
 }
 EXPORT_SYMBOL(geni_se_tx_dma_unprep);
@@ -722,7 +722,7 @@ void geni_se_rx_dma_unprep(struct geni_se *se, dma_addr_t iova, size_t len)
 {
 	struct geni_wrapper *wrapper = se->wrapper;
 
-	if (iova && !dma_mapping_error(wrapper->dev, iova))
+	if (!dma_mapping_error(wrapper->dev, iova))
 		dma_unmap_single(wrapper->dev, iova, len, DMA_FROM_DEVICE);
 }
 EXPORT_SYMBOL(geni_se_rx_dma_unprep);
-- 
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