| From e296c508c0ed3fcbd0c99d66d732af6159e02462 Mon Sep 17 00:00:00 2001 |
| From: Wolfram Sang <wsa+renesas@sang-engineering.com> |
| Date: Sat, 4 Nov 2017 21:20:02 +0100 |
| Subject: [PATCH 0541/1795] i2c: add helpers to ease DMA handling |
| |
| One helper checks if DMA is suitable and optionally creates a bounce |
| buffer, if not. The other function returns the bounce buffer and makes |
| sure the data is properly copied back to the message. |
| |
| Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> |
| Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> |
| Signed-off-by: Wolfram Sang <wsa@the-dreams.de> |
| (cherry picked from commit e94bc5d18be03dac8e9d73d30c5523728edeff76) |
| Signed-off-by: Simon Horman <horms+renesas@verge.net.au> |
| Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> |
| --- |
| drivers/i2c/i2c-core-base.c | 46 +++++++++++++++++++++++++++++++++++++ |
| include/linux/i2c.h | 3 +++ |
| 2 files changed, 49 insertions(+) |
| |
| diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c |
| index 6334f8837371..bdab78795d1e 100644 |
| --- a/drivers/i2c/i2c-core-base.c |
| +++ b/drivers/i2c/i2c-core-base.c |
| @@ -2248,6 +2248,52 @@ void i2c_put_adapter(struct i2c_adapter *adap) |
| } |
| EXPORT_SYMBOL(i2c_put_adapter); |
| |
| +/** |
| + * i2c_get_dma_safe_msg_buf() - get a DMA safe buffer for the given i2c_msg |
| + * @msg: the message to be checked |
| + * @threshold: the minimum number of bytes for which using DMA makes sense |
| + * |
| + * Return: NULL if a DMA safe buffer was not obtained. Use msg->buf with PIO. |
| + * Or a valid pointer to be used with DMA. After use, release it by |
| + * calling i2c_release_dma_safe_msg_buf(). |
| + * |
| + * This function must only be called from process context! |
| + */ |
| +u8 *i2c_get_dma_safe_msg_buf(struct i2c_msg *msg, unsigned int threshold) |
| +{ |
| + if (msg->len < threshold) |
| + return NULL; |
| + |
| + if (msg->flags & I2C_M_DMA_SAFE) |
| + return msg->buf; |
| + |
| + pr_debug("using bounce buffer for addr=0x%02x, len=%d\n", |
| + msg->addr, msg->len); |
| + |
| + if (msg->flags & I2C_M_RD) |
| + return kzalloc(msg->len, GFP_KERNEL); |
| + else |
| + return kmemdup(msg->buf, msg->len, GFP_KERNEL); |
| +} |
| +EXPORT_SYMBOL_GPL(i2c_get_dma_safe_msg_buf); |
| + |
| +/** |
| + * i2c_release_dma_safe_msg_buf - release DMA safe buffer and sync with i2c_msg |
| + * @msg: the message to be synced with |
| + * @buf: the buffer obtained from i2c_get_dma_safe_msg_buf(). May be NULL. |
| + */ |
| +void i2c_release_dma_safe_msg_buf(struct i2c_msg *msg, u8 *buf) |
| +{ |
| + if (!buf || buf == msg->buf) |
| + return; |
| + |
| + if (msg->flags & I2C_M_RD) |
| + memcpy(msg->buf, buf, msg->len); |
| + |
| + kfree(buf); |
| +} |
| +EXPORT_SYMBOL_GPL(i2c_release_dma_safe_msg_buf); |
| + |
| MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>"); |
| MODULE_DESCRIPTION("I2C-Bus main module"); |
| MODULE_LICENSE("GPL"); |
| diff --git a/include/linux/i2c.h b/include/linux/i2c.h |
| index d501d3956f13..1e99342f180f 100644 |
| --- a/include/linux/i2c.h |
| +++ b/include/linux/i2c.h |
| @@ -767,6 +767,9 @@ static inline u8 i2c_8bit_addr_from_msg(const struct i2c_msg *msg) |
| return (msg->addr << 1) | (msg->flags & I2C_M_RD ? 1 : 0); |
| } |
| |
| +u8 *i2c_get_dma_safe_msg_buf(struct i2c_msg *msg, unsigned int threshold); |
| +void i2c_release_dma_safe_msg_buf(struct i2c_msg *msg, u8 *buf); |
| + |
| int i2c_handle_smbus_host_notify(struct i2c_adapter *adap, unsigned short addr); |
| /** |
| * module_i2c_driver() - Helper macro for registering a modular I2C driver |
| -- |
| 2.19.0 |
| |