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Subject[PATCH 4/6] i2c: i2c-stm32: Add generic DMA API
Date
This patch adds a generic DMA API to implement DMA support for i2c-stm32fx
drivers

Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
---
Version history:
v1:
* Initial
---
---
drivers/i2c/busses/i2c-stm32.c | 153 +++++++++++++++++++++++++++++++++++++++++
drivers/i2c/busses/i2c-stm32.h | 37 ++++++++++
2 files changed, 190 insertions(+)
create mode 100644 drivers/i2c/busses/i2c-stm32.c

diff --git a/drivers/i2c/busses/i2c-stm32.c b/drivers/i2c/busses/i2c-stm32.c
new file mode 100644
index 0000000..d75fbcb
--- /dev/null
+++ b/drivers/i2c/busses/i2c-stm32.c
@@ -0,0 +1,153 @@
+/*
+ * i2c-stm32.c
+ *
+ * Copyright (C) M'boumba Cedric Madianga 2017
+ * Author: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
+ *
+ * License terms: GNU General Public License (GPL), version 2
+ */
+
+#include "i2c-stm32.h"
+
+/* Functions for DMA support */
+struct stm32_i2c_dma *stm32_i2c_dma_request(struct device *dev,
+ dma_addr_t phy_addr,
+ u32 txdr_offset,
+ u32 rxdr_offset)
+{
+ struct stm32_i2c_dma *dma;
+ struct dma_slave_config dma_sconfig;
+ int ret;
+
+ dma = devm_kzalloc(dev, sizeof(*dma), GFP_KERNEL);
+ if (!dma)
+ return NULL;
+
+ /* Request and configure I2C TX dma channel */
+ dma->chan_tx = dma_request_slave_channel(dev, "tx");
+ if (!dma->chan_tx) {
+ dev_dbg(dev, "can't request DMA tx channel\n");
+ ret = -EINVAL;
+ goto fail_al;
+ }
+
+ memset(&dma_sconfig, 0, sizeof(dma_sconfig));
+ dma_sconfig.dst_addr = phy_addr + txdr_offset;
+ dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ dma_sconfig.dst_maxburst = 1;
+ dma_sconfig.direction = DMA_MEM_TO_DEV;
+ ret = dmaengine_slave_config(dma->chan_tx, &dma_sconfig);
+ if (ret < 0) {
+ dev_err(dev, "can't configure tx channel\n");
+ goto fail_tx;
+ }
+
+ /* Request and configure I2C RX dma channel */
+ dma->chan_rx = dma_request_slave_channel(dev, "rx");
+ if (!dma->chan_rx) {
+ dev_err(dev, "can't request DMA rx channel\n");
+ ret = -EINVAL;
+ goto fail_tx;
+ }
+
+ memset(&dma_sconfig, 0, sizeof(dma_sconfig));
+ dma_sconfig.src_addr = phy_addr + rxdr_offset;
+ dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ dma_sconfig.src_maxburst = 1;
+ dma_sconfig.direction = DMA_DEV_TO_MEM;
+ ret = dmaengine_slave_config(dma->chan_rx, &dma_sconfig);
+ if (ret < 0) {
+ dev_err(dev, "can't configure rx channel\n");
+ goto fail_rx;
+ }
+
+ init_completion(&dma->dma_complete);
+
+ dev_info(dev, "using %s (tx) and %s (rx) for DMA transfers\n",
+ dma_chan_name(dma->chan_tx), dma_chan_name(dma->chan_rx));
+
+ return dma;
+
+fail_rx:
+ dma_release_channel(dma->chan_rx);
+fail_tx:
+ dma_release_channel(dma->chan_tx);
+fail_al:
+ devm_kfree(dev, dma);
+ dev_info(dev, "can't use DMA\n");
+
+ return NULL;
+}
+
+void stm32_i2c_dma_free(struct stm32_i2c_dma *dma)
+{
+ dma->dma_buf = 0;
+ dma->dma_len = 0;
+
+ dma_release_channel(dma->chan_tx);
+ dma->chan_tx = NULL;
+
+ dma_release_channel(dma->chan_rx);
+ dma->chan_rx = NULL;
+
+ dma->chan_using = NULL;
+}
+
+int stm32_i2c_prep_dma_xfer(struct device *dev, struct stm32_i2c_dma *dma,
+ bool rd_wr, u32 len, u8 *buf,
+ dma_async_tx_callback callback,
+ void *dma_async_param)
+{
+ struct dma_async_tx_descriptor *txdesc;
+ struct device *chan_dev;
+ int ret;
+
+ if (rd_wr) {
+ dma->chan_using = dma->chan_rx;
+ dma->dma_transfer_dir = DMA_DEV_TO_MEM;
+ dma->dma_data_dir = DMA_FROM_DEVICE;
+ } else {
+ dma->chan_using = dma->chan_tx;
+ dma->dma_transfer_dir = DMA_MEM_TO_DEV;
+ dma->dma_data_dir = DMA_TO_DEVICE;
+ }
+
+ dma->dma_len = len;
+ chan_dev = dma->chan_using->device->dev;
+
+ dma->dma_buf = dma_map_single(chan_dev, buf, dma->dma_len,
+ dma->dma_data_dir);
+ if (dma_mapping_error(chan_dev, dma->dma_buf)) {
+ dev_err(dev, "DMA mapping failed\n");
+ return -EINVAL;
+ }
+
+ txdesc = dmaengine_prep_slave_single(dma->chan_using, dma->dma_buf,
+ dma->dma_len,
+ dma->dma_transfer_dir,
+ DMA_PREP_INTERRUPT);
+ if (!txdesc) {
+ dev_err(dev, "Not able to get desc for DMA xfer\n");
+ ret = -EINVAL;
+ goto err;
+ }
+
+ reinit_completion(&dma->dma_complete);
+
+ txdesc->callback = callback;
+ txdesc->callback_param = dma_async_param;
+ ret = dma_submit_error(dmaengine_submit(txdesc));
+ if (ret < 0) {
+ dev_err(dev, "DMA submit failed\n");
+ goto err;
+ }
+
+ dma_async_issue_pending(dma->chan_using);
+
+ return 0;
+
+err:
+ dma_unmap_single(chan_dev, dma->dma_buf, dma->dma_len,
+ dma->dma_data_dir);
+ return ret;
+}
diff --git a/drivers/i2c/busses/i2c-stm32.h b/drivers/i2c/busses/i2c-stm32.h
index d4f9cef..868755f 100644
--- a/drivers/i2c/busses/i2c-stm32.h
+++ b/drivers/i2c/busses/i2c-stm32.h
@@ -11,6 +11,10 @@
#ifndef _I2C_STM32_H
#define _I2C_STM32_H

+#include <linux/dma-direction.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+
enum stm32_i2c_speed {
STM32_I2C_SPEED_STANDARD, /* 100 kHz */
STM32_I2C_SPEED_FAST, /* 400 kHz */
@@ -18,4 +22,37 @@ enum stm32_i2c_speed {
STM32_I2C_SPEED_END,
};

+/**
+ * struct stm32_i2c_dma - DMA specific data
+ * @chan_tx: dma channel for TX transfer
+ * @chan_rx: dma channel for RX transfer
+ * @chan_using: dma channel used for the current transfer (TX or RX)
+ * @dma_buf: dma buffer
+ * @dma_len: dma buffer len
+ * @dma_transfer_dir: dma transfer direction indicator
+ * @dma_data_dir: dma transfer mode indicator
+ * @dma_complete: dma transfer completion
+ */
+struct stm32_i2c_dma {
+ struct dma_chan *chan_tx;
+ struct dma_chan *chan_rx;
+ struct dma_chan *chan_using;
+ dma_addr_t dma_buf;
+ unsigned int dma_len;
+ enum dma_transfer_direction dma_transfer_dir;
+ enum dma_data_direction dma_data_dir;
+ struct completion dma_complete;
+};
+
+struct stm32_i2c_dma *stm32_i2c_dma_request(struct device *dev,
+ dma_addr_t phy_addr,
+ u32 txdr_offset, u32 rxdr_offset);
+
+void stm32_i2c_dma_free(struct stm32_i2c_dma *dma);
+
+int stm32_i2c_prep_dma_xfer(struct device *dev, struct stm32_i2c_dma *dma,
+ bool rd_wr, u32 len, u8 *buf,
+ dma_async_tx_callback callback,
+ void *dma_async_param);
+
#endif /* _I2C_STM32_H */
--
2.7.4
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