This is a note to let you know that I've just added the patch titled
i2c: mxs: ensure that DMA buffers are safe for DMA
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
i2c-mxs-ensure-that-dma-buffers-are-safe-for-dma.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit dd9e6a9ef47d54ea3ec2b818803c1ce693199848
Author: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx>
Date: Mon Feb 13 16:25:50 2023 +0100
i2c: mxs: ensure that DMA buffers are safe for DMA
[ Upstream commit 5190417bdf72c71b65bd9892103c6186816a6e8b ]
We found that after commit 9c46929e7989
("ARM: implement THREAD_INFO_IN_TASK for uniprocessor systems"), the
PCF85063 RTC driver stopped working on i.MX28 due to regmap_bulk_read()
reading bogus data into a stack buffer. This is caused by the i2c-mxs
driver using DMA transfers even for messages without the I2C_M_DMA_SAFE
flag, and the aforementioned commit enabling vmapped stacks.
As the MXS I2C controller requires DMA for reads of >4 bytes, DMA can't be
disabled, so the issue is fixed by using i2c_get_dma_safe_msg_buf() to
create a bounce buffer when needed.
Fixes: 9c46929e7989 ("ARM: implement THREAD_INFO_IN_TASK for uniprocessor systems")
Signed-off-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx>
Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c
index d113bed795452..e0f3b3545cfe4 100644
--- a/drivers/i2c/busses/i2c-mxs.c
+++ b/drivers/i2c/busses/i2c-mxs.c
@@ -171,7 +171,7 @@ static void mxs_i2c_dma_irq_callback(void *param)
}
static int mxs_i2c_dma_setup_xfer(struct i2c_adapter *adap,
- struct i2c_msg *msg, uint32_t flags)
+ struct i2c_msg *msg, u8 *buf, uint32_t flags)
{
struct dma_async_tx_descriptor *desc;
struct mxs_i2c_dev *i2c = i2c_get_adapdata(adap);
@@ -226,7 +226,7 @@ static int mxs_i2c_dma_setup_xfer(struct i2c_adapter *adap,
}
/* Queue the DMA data transfer. */
- sg_init_one(&i2c->sg_io[1], msg->buf, msg->len);
+ sg_init_one(&i2c->sg_io[1], buf, msg->len);
dma_map_sg(i2c->dev, &i2c->sg_io[1], 1, DMA_FROM_DEVICE);
desc = dmaengine_prep_slave_sg(i2c->dmach, &i2c->sg_io[1], 1,
DMA_DEV_TO_MEM,
@@ -259,7 +259,7 @@ static int mxs_i2c_dma_setup_xfer(struct i2c_adapter *adap,
/* Queue the DMA data transfer. */
sg_init_table(i2c->sg_io, 2);
sg_set_buf(&i2c->sg_io[0], &i2c->addr_data, 1);
- sg_set_buf(&i2c->sg_io[1], msg->buf, msg->len);
+ sg_set_buf(&i2c->sg_io[1], buf, msg->len);
dma_map_sg(i2c->dev, i2c->sg_io, 2, DMA_TO_DEVICE);
desc = dmaengine_prep_slave_sg(i2c->dmach, i2c->sg_io, 2,
DMA_MEM_TO_DEV,
@@ -563,6 +563,7 @@ static int mxs_i2c_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg,
struct mxs_i2c_dev *i2c = i2c_get_adapdata(adap);
int ret;
int flags;
+ u8 *dma_buf;
int use_pio = 0;
unsigned long time_left;
@@ -588,13 +589,20 @@ static int mxs_i2c_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg,
if (ret && (ret != -ENXIO))
mxs_i2c_reset(i2c);
} else {
+ dma_buf = i2c_get_dma_safe_msg_buf(msg, 1);
+ if (!dma_buf)
+ return -ENOMEM;
+
reinit_completion(&i2c->cmd_complete);
- ret = mxs_i2c_dma_setup_xfer(adap, msg, flags);
- if (ret)
+ ret = mxs_i2c_dma_setup_xfer(adap, msg, dma_buf, flags);
+ if (ret) {
+ i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
return ret;
+ }
time_left = wait_for_completion_timeout(&i2c->cmd_complete,
msecs_to_jiffies(1000));
+ i2c_put_dma_safe_msg_buf(dma_buf, msg, true);
if (!time_left)
goto timeout;
