FROMLIST: i2c: i2c-qcom-geni: Parse Error correctly in i2c GSI mode

I2C driver currently reports "DMA txn failed" error even though it's
NACK OR BUS_PROTO OR ARB_LOST. Detect NACK error when no device ACKs
on the bus instead of generic transfer failure which doesn't give any
specific clue.

Make Changes inside i2c driver callback handler function
i2c_gpi_cb_result() to parse these errors and make sure GSI driver
stores the error status during error interrupt.

Co-developed-by: Viken Dadhaniya <quic_vdadhani@quicinc.com>
Signed-off-by: Viken Dadhaniya <quic_vdadhani@quicinc.com>
Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Author: Mukesh Kumar Savaliya

drivers/dma/qcom/gpi.c

@@ -1072,7 +1072,17 @@ static void gpi_process_xfer_compl_event(struct gchan *gchan,
 	dev_dbg(gpii->gpi_dev->dev, "Residue %d\n", result.residue);
 
 	dma_cookie_complete(&vd->tx);
-	dmaengine_desc_get_callback_invoke(&vd->tx, &result);
+	if (gchan->protocol == QCOM_GPI_I2C) {
+		struct dmaengine_desc_callback cb;
+		struct gpi_i2c_result *i2c;
+
+		dmaengine_desc_get_callback(&vd->tx, &cb);
+		i2c = cb.callback_param;
+		i2c->status = compl_event->status;
+		dmaengine_desc_callback_invoke(&cb, &result);
+	} else {
+		dmaengine_desc_get_callback_invoke(&vd->tx, &result);
+	}
 
 gpi_free_desc:
 	spin_lock_irqsave(&gchan->vc.lock, flags);

drivers/i2c/busses/i2c-qcom-geni.c

@@ -2,6 +2,7 @@
 // Copyright (c) 2017-2018, The Linux Foundation. All rights reserved.
 
 #include <linux/acpi.h>
+#include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/dmaengine.h>
 #include <linux/dma-mapping.h>
@@ -67,6 +68,7 @@ enum geni_i2c_err_code {
 	GENI_TIMEOUT,
 };
 
+#define I2C_DMA_TX_IRQ_MASK	GENMASK(12, 5)
 #define DM_I2C_CB_ERR		((BIT(NACK) | BIT(BUS_PROTO) | BIT(ARB_LOST)) \
 									<< 5)
 
@@ -100,6 +102,7 @@ struct geni_i2c_dev {
 	struct dma_chan *rx_c;
 	bool gpi_mode;
 	bool abort_done;
+	struct gpi_i2c_result i2c_result;
 };
 
 struct geni_i2c_desc {
@@ -499,9 +502,18 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 
 static void i2c_gpi_cb_result(void *cb, const struct dmaengine_result *result)
 {
-	struct geni_i2c_dev *gi2c = cb;
-
-	if (result->result != DMA_TRANS_NOERROR) {
+	struct gpi_i2c_result *i2c_res = cb;
+	struct geni_i2c_dev *gi2c = container_of(i2c_res, struct geni_i2c_dev, i2c_result);
+	u32 status;
+
+	status = FIELD_GET(I2C_DMA_TX_IRQ_MASK, i2c_res->status);
+	if (status == BIT(NACK)) {
+		geni_i2c_err(gi2c, NACK);
+	} else if (status == BIT(BUS_PROTO)) {
+		geni_i2c_err(gi2c, BUS_PROTO);
+	} else if (status == BIT(ARB_LOST)) {
+		geni_i2c_err(gi2c, ARB_LOST);
+	} else if (result->result != DMA_TRANS_NOERROR) {
 		dev_err(gi2c->se.dev, "DMA txn failed:%d\n", result->result);
 		gi2c->err = -EIO;
 	} else if (result->residue) {
@@ -583,7 +595,7 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 	}
 
 	desc->callback_result = i2c_gpi_cb_result;
-	desc->callback_param = gi2c;
+	desc->callback_param = &gi2c->i2c_result;
 
 	dmaengine_submit(desc);
 	*buf = dma_buf;

include/linux/dma/qcom-gpi-dma.h

@@ -80,4 +80,14 @@ struct gpi_i2c_config {
 	bool multi_msg;
 };
 
+/**
+ * struct gpi_i2c_result - i2c transfer status result in GSI mode
+ *
+ * @status: store txfer status value as part of callback
+ *
+ */
+struct gpi_i2c_result {
+	u32 status;
+};
+
 #endif /* QCOM_GPI_DMA_H */