STM32: Add dma_select_channel

dma_select_channel selects which stream (peripheral) to be used on a
specific channel. Some STM32 chips simply logically OR requests, thus
do not require this selection.

BUG=none
BRANCH=tot
TEST=make buildall && make tests. Verified on stm32l476g-eval.

Change-Id: I7b64b78bdec80658992f58cb4c94ade972a1081c
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/340107
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>

4 files changed, 38 insertions, 0 deletions

diff --git a/chip/stm32/config_chip.h b/chip/stm32/config_chip.h
index f77fdf059e..87ebd21c09 100644
--- a/chip/stm32/config_chip.h
+++ b/chip/stm32/config_chip.h
@@ -96,6 +96,9 @@
 /* Use DMA */
 #define CONFIG_DMA
 
+/* Number of peripheral request signals per DMA channel */
+#define STM32_DMA_PERIPHERALS_PER_CHANNEL	4
+
 /*
  * Use DMA for UART transmit for all platforms.  DMA for UART receive is
  * enabled on a per-chip basis because it doesn't seem to work reliably on
diff --git a/chip/stm32/dma.c b/chip/stm32/dma.c
index 56723e1be1..d169cf7f45 100644
--- a/chip/stm32/dma.c
+++ b/chip/stm32/dma.c
@@ -59,6 +59,22 @@ stm32_dma_chan_t *dma_get_channel(enum dma_channel channel)
 	return &dma->chan[channel % STM32_DMAC_PER_CTLR];
 }
 
+#ifdef STM32_DMA_CSELR
+void dma_select_channel(enum dma_channel channel, unsigned char stream)
+{
+	/* Local channel # starting from 0 on each DMA controller */
+	const unsigned char ch = channel % STM32_DMAC_PER_CTLR;
+	const unsigned char shift = STM32_DMA_PERIPHERALS_PER_CHANNEL;
+	const unsigned char mask = (1 << shift) - 1;
+	uint32_t val;
+
+	ASSERT(ch < STM32_DMAC_PER_CTLR);
+	ASSERT(stream <= mask);
+	val = STM32_DMA_CSELR(channel) & ~(mask << ch * shift);
+	STM32_DMA_CSELR(channel) = val | (stream << ch * shift);
+}
+#endif
+
 void dma_disable(enum dma_channel channel)
 {
 	stm32_dma_chan_t *chan = dma_get_channel(channel);
diff --git a/chip/stm32/registers.h b/chip/stm32/registers.h
index 283fd44498..74eee526cb 100644
--- a/chip/stm32/registers.h
+++ b/chip/stm32/registers.h
@@ -1233,6 +1233,9 @@ typedef volatile struct stm32_dma_regs stm32_dma_regs_t;
 
 #define STM32_DMA_REGS(channel) \
 	((channel) < STM32_DMAC_PER_CTLR ? STM32_DMA1_REGS : STM32_DMA2_REGS)
+#define STM32_DMA_CSELR(channel) \
+	REG32(((channel) < STM32_DMAC_PER_CTLR ? \
+			STM32_DMA1_BASE : STM32_DMA2_BASE)  + 0xA8)
 #else
 #define STM32_DMA_REGS(channel) STM32_DMA1_REGS
 #endif
diff --git a/chip/stm32/stm32-dma.h b/chip/stm32/stm32-dma.h
new file mode 100644
index 0000000000..06233b9c93
--- /dev/null
+++ b/chip/stm32/stm32-dma.h
@@ -0,0 +1,16 @@
+/* Copyright 2016 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/**
+ * Select DMA stream-channel mapping
+ *
+ * This selects which stream (peripheral) to be used on a specific channel.
+ * Some STM32 chips simply logically OR requests, thus do not require this
+ * selection.
+ *
+ * @param channel: (Global) channel # base 0 (Note some STM32s use base 1)
+ * @param peripheral: Refer to the TRM for 'peripheral request signals'
+ */
+void dma_select_channel(enum dma_channel channel, unsigned char stream);