[PATCH v1 2/2] i3c: mipi-i3c-hci: Use DMA-safe buffer for I2C transfers
Jarkko Nikula
jarkko.nikula at linux.intel.com
Wed Jan 22 00:28:01 PST 2025
On 1/21/25 1:07 PM, Billy Tsai wrote:
> The i2c_get_dma_safe_msg_buf function is used to ensure safe handling of
> I2C messages in HCI DMA mode.
>
> Signed-off-by: Billy Tsai <billy_tsai at aspeedtech.com>
> ---
> drivers/i3c/master/mipi-i3c-hci/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
> index a408feac3e9e..3567cd566339 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/core.c
> +++ b/drivers/i3c/master/mipi-i3c-hci/core.c
> @@ -382,7 +382,7 @@ static int i3c_hci_i2c_xfers(struct i2c_dev_desc *dev,
> return -ENOMEM;
>
> for (i = 0; i < nxfers; i++) {
> - xfer[i].data = i2c_xfers[i].buf;
> + xfer[i].data = i2c_get_dma_safe_msg_buf(&i2c_xfers[i], 1);
> xfer[i].data_len = i2c_xfers[i].len;
> xfer[i].rnw = i2c_xfers[i].flags & I2C_M_RD;
> hci->cmd->prep_i2c_xfer(hci, dev, &xfer[i]);
This allow to remove calls to i3c_hci_alloc_safe_xfer_buf() and
i3c_hci_free_safe_xfer_buf() in i3c_hci_i2c_xfers().
I was pondering the i2c_get_dma_safe_msg_buf() when making commit
4afd72876942 ("i3c: mipi-i3c-hci: Add DMA bounce buffer for private
transfers") but decided to reuse the same (own) helper for both
i3c_hci_priv_xfers() and i3c_hci_i2c_xfers().
In that sense I'd modify the commit log a bit that instead of ensuring
safe handling patch switches from custom helper to
i2c_get_dma_safe_msg_buf() and i2c_put_dma_safe_msg_buf() (please note
the comment from Wolfram).
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