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SubjectRe: [PATCH v2] Input: elants_i2c - Use DMA safe i2c when possible
On Wed, Oct 10, 2018 at 01:00:17PM -0700, Stephen Boyd wrote:
> This irq handler is always reading bytes from the device into a
> kmalloced buffer, so it's safe to mark this transaction as DMA safe.
> This avoids bouncing the buffer when an i2c controller decides to use
> DMA for a transaction.
>
> Cc: Wolfram Sang <wsa@the-dreams.de>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>

Changed patch description a bit (now that we are actually making the
buffer DMA-safe) and applied, thank you.

> ---
>
> Changes from v1:
> * Moved buf to end of structure to keep it cacheline aligned and DMA
> safe
>
> drivers/input/touchscreen/elants_i2c.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/input/touchscreen/elants_i2c.c b/drivers/input/touchscreen/elants_i2c.c
> index d21ca39b0fdb..f2cb23121833 100644
> --- a/drivers/input/touchscreen/elants_i2c.c
> +++ b/drivers/input/touchscreen/elants_i2c.c
> @@ -147,10 +147,11 @@ struct elants_data {
> u8 cmd_resp[HEADER_SIZE];
> struct completion cmd_done;
>
> - u8 buf[MAX_PACKET_SIZE];
> -
> bool wake_irq_enabled;
> bool keep_power_in_suspend;
> +
> + /* Must be last to be used for DMA operations */
> + u8 buf[MAX_PACKET_SIZE] ____cacheline_aligned;
> };
>
> static int elants_i2c_send(struct i2c_client *client,
> @@ -863,7 +864,7 @@ static irqreturn_t elants_i2c_irq(int irq, void *_dev)
> int i;
> int len;
>
> - len = i2c_master_recv(client, ts->buf, sizeof(ts->buf));
> + len = i2c_master_recv_dmasafe(client, ts->buf, sizeof(ts->buf));
> if (len < 0) {
> dev_err(&client->dev, "%s: failed to read data: %d\n",
> __func__, len);
> --
> Sent by a computer through tubes
>

--
Dmitry

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