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Wed, 10 Oct 2018 17:11:17 -0700 (PDT) Date: Wed, 10 Oct 2018 17:11:14 -0700 From: Dmitry Torokhov To: Stephen Boyd Cc: linux-kernel@vger.kernel.org, linux-input@vger.kernel.org, Wolfram Sang Subject: Re: [PATCH v2] Input: elants_i2c - Use DMA safe i2c when possible Message-ID: <20181011001114.GA173303@dtor-ws> References: <20181010200017.255874-1-swboyd@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181010200017.255874-1-swboyd@chromium.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > Signed-off-by: Stephen Boyd 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