[PATCH v2 15/25] mtd: nand: qcom: DMA mapping support for register read buffer

[Abhishek Sahu]

The EBI2 NAND directly remaps register read buffer with
dma_map_sg. The QPIC NAND will give register read buffer in its
command descriptor and the command descriptor will be mapped with
dma_map_sg instead of register read buffer. This command
descriptor will contain the dma address of the register read
buffer.

This patch adds the DMA mapping support for register read buffer.
This buffer will be DMA mapped during allocation time. Before
starting of any operation, this buffer will be synced for device
operation and after operation completion, it will be synced for
CPU.

Signed-off-by: Abhishek Sahu <absahu at codeaurora.org>
---
 drivers/mtd/nand/qcom_nandc.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/drivers/mtd/nand/qcom_nandc.c b/drivers/mtd/nand/qcom_nandc.c
index cb2b245..f49c3da 100644
--- a/drivers/mtd/nand/qcom_nandc.c
+++ b/drivers/mtd/nand/qcom_nandc.c
@@ -229,6 +229,7 @@ struct nandc_regs {
  *				by upper layers directly
  * @buf_size/count/start:	markers for chip->read_buf/write_buf functions
  * @reg_read_buf:		local buffer for reading back registers via DMA
+ * @reg_read_buf_phys:		contains dma address for register read buffer
  * @reg_read_pos:		marker for data read in reg_read_buf
  *
  * @regs:			a contiguous chunk of memory for DMA register
@@ -271,6 +272,7 @@ struct qcom_nand_controller {
 	int		buf_start;
 
 	__le32 *reg_read_buf;
+	dma_addr_t reg_read_buf_phys;
 	int reg_read_pos;
 
 	struct nandc_regs *regs;
@@ -363,6 +365,24 @@ static inline void nandc_write(struct qcom_nand_controller *nandc, int offset,
 	iowrite32(val, nandc->base + offset);
 }
 
+static inline void nandc_read_buffer_sync(struct qcom_nand_controller *nandc,
+					  bool is_cpu)
+{
+	if (!nandc->props->is_bam)
+		return;
+
+	if (is_cpu)
+		dma_sync_single_for_cpu(nandc->dev, nandc->reg_read_buf_phys,
+					MAX_REG_RD *
+					sizeof(*nandc->reg_read_buf),
+					DMA_FROM_DEVICE);
+	else
+		dma_sync_single_for_device(nandc->dev, nandc->reg_read_buf_phys,
+					   MAX_REG_RD *
+					   sizeof(*nandc->reg_read_buf),
+					   DMA_FROM_DEVICE);
+}
+
 static __le32 *offset_to_nandc_reg(struct nandc_regs *regs, int offset)
 {
 	switch (offset) {
@@ -847,6 +867,7 @@ static void free_descs(struct qcom_nand_controller *nandc)
 static void clear_read_regs(struct qcom_nand_controller *nandc)
 {
 	nandc->reg_read_pos = 0;
+	nandc_read_buffer_sync(nandc, false);
 }
 
 static void pre_command(struct qcom_nand_host *host, int command)
@@ -876,6 +897,7 @@ static void parse_erase_write_errors(struct qcom_nand_host *host, int command)
 	int i;
 
 	num_cw = command == NAND_CMD_PAGEPROG ? ecc->steps : 1;
+	nandc_read_buffer_sync(nandc, true);
 
 	for (i = 0; i < num_cw; i++) {
 		u32 flash_status = le32_to_cpu(nandc->reg_read_buf[i]);
@@ -897,6 +919,7 @@ static void post_command(struct qcom_nand_host *host, int command)
 
 	switch (command) {
 	case NAND_CMD_READID:
+		nandc_read_buffer_sync(nandc, true);
 		memcpy(nandc->data_buffer, nandc->reg_read_buf,
 		       nandc->buf_count);
 		break;
@@ -1060,6 +1083,7 @@ static int parse_read_errors(struct qcom_nand_host *host, u8 *data_buf,
 	int i;
 
 	buf = (struct read_stats *)nandc->reg_read_buf;
+	nandc_read_buffer_sync(nandc, true);
 
 	for (i = 0; i < ecc->steps; i++, buf++) {
 		u32 flash, buffer, erased_cw;
@@ -1996,6 +2020,16 @@ static int qcom_nandc_alloc(struct qcom_nand_controller *nandc)
 		return -ENOMEM;
 
 	if (nandc->props->is_bam) {
+		nandc->reg_read_buf_phys =
+			dma_map_single(nandc->dev, nandc->reg_read_buf,
+				       MAX_REG_RD *
+				       sizeof(*nandc->reg_read_buf),
+				       DMA_FROM_DEVICE);
+		if (dma_mapping_error(nandc->dev, nandc->reg_read_buf_phys)) {
+			dev_err(nandc->dev, "failed to DMA MAP reg buffer\n");
+			return -EIO;
+		}
+
 		nandc->tx_chan = dma_request_slave_channel(nandc->dev, "tx");
 		if (!nandc->tx_chan) {
 			dev_err(nandc->dev, "failed to request tx channel\n");
@@ -2033,6 +2067,12 @@ static int qcom_nandc_alloc(struct qcom_nand_controller *nandc)
 static void qcom_nandc_unalloc(struct qcom_nand_controller *nandc)
 {
 	if (nandc->props->is_bam) {
+		if (!dma_mapping_error(nandc->dev, nandc->reg_read_buf_phys))
+			dma_unmap_single(nandc->dev, nandc->reg_read_buf_phys,
+					 MAX_REG_RD *
+					 sizeof(*nandc->reg_read_buf),
+					 DMA_FROM_DEVICE);
+
 		if (nandc->tx_chan)
 			dma_release_channel(nandc->tx_chan);
 
-- 
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