[U-Boot] [PATCH 13/18] sf: add helper function to set the number of dummy bytes

[Cyrille Pitchen]

This patch adds a helper function to ease the conversion between a number
of dummy clock cycles and number of bytes.

Actually this number of bytes depends on both the number of dummy clock
cycles and SPI protocol used by (Fast) Read commands.

This new function is exported so it can be used by other drivers.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen at atmel.com>
---
 drivers/mtd/spi/sf_internal.h |  6 ++++++
 drivers/mtd/spi/spi_flash.c   | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/drivers/mtd/spi/sf_internal.h b/drivers/mtd/spi/sf_internal.h
index 26d359707d5b..86a0276f8518 100644
--- a/drivers/mtd/spi/sf_internal.h
+++ b/drivers/mtd/spi/sf_internal.h
@@ -240,6 +240,12 @@ typedef int (*spi_flash_read_fn)(struct spi_flash *, u32, size_t, void *);
 int spi_flash_read_alg(struct spi_flash *flash, u32 offset, size_t len,
 		void *data, spi_flash_read_fn read_fn);
 
+/*
+ * Helper function to compute the number of dummy bytes from both the number
+ * of dummy cycles and the SPI protocol used for (Fast) Read operations.
+ */
+int spi_flash_set_dummy_byte(struct spi_flash *flash, u8 num_dummy_cycles);
+
 #ifdef CONFIG_SPI_FLASH_MTD
 int spi_flash_mtd_register(struct spi_flash *flash);
 void spi_flash_mtd_unregister(void);
diff --git a/drivers/mtd/spi/spi_flash.c b/drivers/mtd/spi/spi_flash.c
index 5d641bbb8301..01a073d81eb9 100644
--- a/drivers/mtd/spi/spi_flash.c
+++ b/drivers/mtd/spi/spi_flash.c
@@ -882,6 +882,17 @@ int stm_unlock(struct spi_flash *flash, u32 ofs, size_t len)
 }
 #endif
 
+int spi_flash_set_dummy_byte(struct spi_flash *flash, u8 num_dummy_cycles)
+{
+	u8 dummy_bits = num_dummy_cycles;
+
+	dummy_bits *= SPI_FLASH_PROTO_ADR_FROM_PROTO(flash->read_proto);
+	if (dummy_bits & 0x7)
+		return -EINVAL;
+
+	flash->dummy_byte = dummy_bits >> 3;
+	return 0;
+}
 
 #ifdef CONFIG_SPI_FLASH_MACRONIX
 static int macronix_quad_enable(struct spi_flash *flash)
-- 
1.8.2.2