From 5af5dd085ad9b029c8cdeaf57b317adae0228a0c Mon Sep 17 00:00:00 2001 From: Kai-Heng Feng Date: Thu, 25 Apr 2019 12:43:33 +0800 Subject: [PATCH] i2c: add helpers to ease DMA handling BugLink: https://bugs.launchpad.net/bugs/1787775 From: Wolfram Sang 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 Signed-off-by: Wolfram Sang Signed-off-by: Wolfram Sang (cherry picked from commit e94bc5d18be03dac8e9d73d30c5523728edeff76) Signed-off-by: Kai-Heng Feng Acked-by: Khalid Elmously Acked-by: Kleber Souza Signed-off-by: Khalid Elmously --- 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 f7829a74140c..b6d3dcb62992 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -2265,6 +2265,52 @@ 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 "); MODULE_DESCRIPTION("I2C-Bus main module"); MODULE_LICENSE("GPL"); diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 0f774406fad0..a0b57de91e21 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -769,6 +769,9 @@ 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 -- 2.39.2