[U-Boot] [PATCH 1/4 v2] spi: spi-mem: Use 2 SPI messages instead of a single full-duplex one

Stefan Roese
2018-08-07T12:16:52Z

Some SPI controller do not support full-duplex SPI transfers. This patch
changes the SPI transfer into 2 separate transfers - or 1, if no data is
to transmitted.

With this change, no buffers need to be allocated anymore. We use the
TX and RX buffers that are passed to spi_mem_exec_op() directly.

Signed-off-by: Stefan Roese <sr@denx.de>
Suggested-by: Boris Brezillon <boris.brezillon@bootlin.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Boris Brezillon <boris.brezillon@bootlin.com>
Cc: Jagan Teki <jagan@openedev.com>
---
v2:
- Replaces patch "spi: spi-mem: Add optional half-duplex SPI transfer mode"
from first patchset version
- No compile-time option but the default to use 2 separate SPI messages
to transfer the command and data

drivers/spi/spi-mem.c | 74 +++++++++++++++++++++++--------------------
1 file changed, 39 insertions(+), 35 deletions(-)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 07ce799170..84e33aa979 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -15,6 +15,8 @@
#include <spi-mem.h>
#endif

+#define OP_BUFFER_SIZE_MAX 16 /* Max size for cmd + addr + dummy */
+
#ifndef __UBOOT__
/**
* spi_controller_dma_map_mem_op_data() - DMA-map the buffer attached to a
@@ -200,8 +202,12 @@ int spi_mem_exec_op(struct spi_slave *slave, const struct spi_mem_op *op)
bool tx_data = op->data.nbytes && (op->data.dir == SPI_MEM_DATA_OUT);
struct udevice *bus = slave->dev->parent;
struct dm_spi_ops *ops = spi_get_ops(bus);
- unsigned int xfer_len, pos = 0;
- u8 *tx_buf, *rx_buf = NULL;
+ unsigned int pos = 0;
+ const u8 *tx_buf;
+ u8 *rx_buf;
+ u8 op_buf[OP_BUFFER_SIZE_MAX];
+ int op_len;
+ u32 flag;
int ret;
int i;

@@ -330,67 +336,65 @@ int spi_mem_exec_op(struct spi_slave *slave, const struct spi_mem_op *op)
return -ENOTSUPP;
}

- xfer_len = sizeof(op->cmd.opcode) + op->addr.nbytes +
- op->dummy.nbytes + op->data.nbytes;
+ tx_buf = op->data.buf.out;
+ rx_buf = op->data.buf.in;

- /*
- * Allocate a buffer to transmit the CMD, ADDR cycles with kmalloc() so
- * we're guaranteed that this buffer is DMA-able, as required by the
- * SPI layer.
- */
- tx_buf = kzalloc(xfer_len, GFP_KERNEL);
- if (!tx_buf)
- return -ENOMEM;
-
- if (rx_data) {
- rx_buf = kzalloc(xfer_len, GFP_KERNEL);
- if (!rx_buf)
- return -ENOMEM;
+ op_len = sizeof(op->cmd.opcode) + op->addr.nbytes + op->dummy.nbytes;
+ if (op_len > OP_BUFFER_SIZE_MAX) {
+ printf("Length for cmd+addr+dummy too big (%d)\n", op_len);
+ return -EIO;
}
+ memset(op_buf, 0x00, op_len);

ret = spi_claim_bus(slave);
if (ret < 0)
return ret;

- tx_buf[pos++] = op->cmd.opcode;
+ op_buf[pos++] = op->cmd.opcode;

if (op->addr.nbytes) {
for (i = 0; i < op->addr.nbytes; i++)
- tx_buf[pos + i] = op->addr.val >>
- (8 * (op->addr.nbytes - i - 1));
+ op_buf[pos + i] = op->addr.val >>
+ (8 * (op->addr.nbytes - i - 1));

pos += op->addr.nbytes;
}

- if (op->dummy.nbytes) {
- memset(tx_buf + pos, 0xff, op->dummy.nbytes);
- pos += op->dummy.nbytes;
+ if (op->dummy.nbytes)
+ memset(op_buf + pos, 0xff, op->dummy.nbytes);
+
+ /* 1st transfer: opcode + address + dummy cycles */
+ flag = SPI_XFER_BEGIN;
+ /* Make sure to set END bit if no tx or rx data messages follow */
+ if (!tx_data && !rx_data)
+ flag |= SPI_XFER_END;
+ ret = spi_xfer(slave, op_len * 8, op_buf, NULL, flag);
+
+ if (tx_data) {
+ /* 2nd transfer a: tx data path */
+ ret = spi_xfer(slave, op->data.nbytes * 8, tx_buf, NULL,
+ SPI_XFER_END);
}

- if (tx_data)
- memcpy(tx_buf + pos, op->data.buf.out, op->data.nbytes);
+ if (rx_data) {
+ /* 2nd transfer b: rx data path */
+ ret = spi_xfer(slave, op->data.nbytes * 8, NULL, rx_buf,
+ SPI_XFER_END);
+ }

- ret = spi_xfer(slave, xfer_len * 8, tx_buf, rx_buf,
- SPI_XFER_BEGIN | SPI_XFER_END);
spi_release_bus(slave);

for (i = 0; i < pos; i++)
- debug("%02x ", tx_buf[i]);
+ debug("%02x ", op_buf[i]);
debug("| [%dB %s] ",
tx_data || rx_data ? op->data.nbytes : 0,
tx_data || rx_data ? (tx_data ? "out" : "in") : "-");
- for (; i < xfer_len; i++)
+ for (i = 0; i < op->data.nbytes; i++)
debug("%02x ", tx_data ? tx_buf[i] : rx_buf[i]);
debug("[ret %d]\n", ret);

if (ret < 0)
return ret;
-
- if (rx_data)
- memcpy(op->data.buf.in, rx_buf + pos, op->data.nbytes);
-
- kfree(tx_buf);
- kfree(rx_buf);
#endif /* __UBOOT__ */

return 0;
--
2.18.0