linux-kernel - [PATCH v4 5/9] spi: spi-mem: Mark dummy transfers by setting dummy

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Message-ID: <1608236927-28701-6-git-send-email-skomatineni@nvidia.com>
Date:   Thu, 17 Dec 2020 12:28:43 -0800
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <broonie@...nel.org>, <robh+dt@...nel.org>, <lukas@...ner.de>
CC:     <skomatineni@...dia.com>, <bbrezillon@...nel.org>,
        <p.yadav@...com>, <tudor.ambarus@...rochip.com>,
        <linux-spi@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: [PATCH v4 5/9] spi: spi-mem: Mark dummy transfers by setting dummy_data bit

This patch marks dummy transfer by setting dummy_data bit to 1.

Controllers supporting dummy transfer by hardware use this bit field
to skip software transfer of dummy bytes and use hardware dummy bytes
transfer.

Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
---
 drivers/spi/spi-mem.c   | 1 +
 include/linux/spi/spi.h | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index f3a3f19..c64371c 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -354,6 +354,7 @@ int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
 		xfers[xferpos].tx_buf = tmpbuf + op->addr.nbytes + 1;
 		xfers[xferpos].len = op->dummy.nbytes;
 		xfers[xferpos].tx_nbits = op->dummy.buswidth;
+		xfers[xferpos].dummy_data = 1;
 		spi_message_add_tail(&xfers[xferpos], &msg);
 		xferpos++;
 		totalxferlen += op->dummy.nbytes;
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index aa09fdc..708f2f5 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -827,6 +827,7 @@ extern void spi_res_release(struct spi_controller *ctlr,
  *      transfer. If 0 the default (from @spi_device) is used.
  * @bits_per_word: select a bits_per_word other than the device default
  *      for this transfer. If 0 the default (from @spi_device) is used.
+ * @dummy_data: indicates transfer is dummy bytes transfer.
  * @cs_change: affects chipselect after this transfer completes
  * @cs_change_delay: delay between cs deassert and assert when
  *      @cs_change is set and @spi_transfer is not the last in @spi_message
@@ -939,6 +940,7 @@ struct spi_transfer {
 	struct sg_table tx_sg;
 	struct sg_table rx_sg;
 
+	unsigned	dummy_data:1;
 	unsigned	cs_change:1;
 	unsigned	tx_nbits:3;
 	unsigned	rx_nbits:3;
-- 
2.7.4