From 9d24a480aecf368382d70c4a84328e13f8df0e1d Mon Sep 17 00:00:00 2001
From: Zachary Crockett <towynlin@gmail.com>
Date: Tue, 26 Feb 2013 17:30:48 +0800
Subject: [PATCH] Implement SPI clean disable from TODO comment

---
 .../libopencm3/stm32/common/spi_common_all.h  |  1 +
 lib/stm32/common/spi_common_all.c             | 35 +++++++++++++++++--
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/include/libopencm3/stm32/common/spi_common_all.h b/include/libopencm3/stm32/common/spi_common_all.h
index 57b1465d..a3f1d5bc 100644
--- a/include/libopencm3/stm32/common/spi_common_all.h
+++ b/include/libopencm3/stm32/common/spi_common_all.h
@@ -350,6 +350,7 @@ void spi_reset(u32 spi_peripheral);
 int spi_init_master(u32 spi, u32 br, u32 cpol, u32 cpha, u32 dff, u32 lsbfirst);
 void spi_enable(u32 spi);
 void spi_disable(u32 spi);
+void spi_clean_disable(u32 spi);
 void spi_write(u32 spi, u16 data);
 void spi_send(u32 spi, u16 data);
 u16 spi_read(u32 spi);
diff --git a/lib/stm32/common/spi_common_all.c b/lib/stm32/common/spi_common_all.c
index 2e6473d0..184654e8 100644
--- a/lib/stm32/common/spi_common_all.c
+++ b/lib/stm32/common/spi_common_all.c
@@ -163,9 +163,6 @@ void spi_enable(u32 spi)
 
 The SPI peripheral is disabled.
 
-@todo  Follow procedure from section 23.3.8 in the TRM. 
-(possibly create a "clean disable" function separately)
-
 @param[in] spi Unsigned int32. SPI peripheral identifier @ref spi_reg_base.
 */
 
@@ -178,6 +175,38 @@ void spi_disable(u32 spi)
 	SPI_CR1(spi) = reg32;
 }
 
+/*-----------------------------------------------------------------------------*/
+/** @brief SPI Clean Disable.
+
+Disable the SPI peripheral according to the procedure in section 23.3.8 of the
+reference manual.  This prevents corruption of any ongoing transfers and
+prevents the BSY flag from becoming unreliable.
+
+@param[in] spi Unsigned int32. SPI peripheral identifier @ref spi_reg_base.
+@returns data Unsigned int16. 8 or 16 bit data from final read.
+*/
+
+u16 spi_clean_disable(u32 spi)
+{
+	/* Wait to receive last data */
+	while (!(SPI_SR(spi) & SPI_SR_RXNE))
+		;
+
+	u16 data = SPI_DR(spi);
+
+	/* Wait to transmit last data */
+	while (!(SPI_SR(spi) & SPI_SR_TXE))
+		;
+
+	/* Wait until not busy */
+	while (SPI_SR(spi) & SPI_SR_BSY)
+		;
+
+	SPI_CR1(spi) &= ~SPI_CR1_SPE;
+
+	return data;
+}
+
 /*-----------------------------------------------------------------------------*/
 /** @brief SPI Data Write.