From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-lf0-f44.google.com ([209.85.215.44]:36813 "EHLO mail-lf0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753693AbdGSJfs (ORCPT ); Wed, 19 Jul 2017 05:35:48 -0400 Received: by mail-lf0-f44.google.com with SMTP id d78so26006817lfg.3 for ; Wed, 19 Jul 2017 02:35:47 -0700 (PDT) Date: Wed, 19 Jul 2017 11:35:45 +0200 From: Niklas =?iso-8859-1?Q?S=F6derlund?= To: Wolfram Sang Cc: linux-i2c@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-media@vger.kernel.org, linux-input@vger.kernel.org, linux-iio@vger.kernel.org, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/4] i2c: sh_mobile: use helper to decide if DMA is useful Message-ID: <20170719093544.GN28538@bigcity.dyn.berto.se> References: <20170718102339.28726-1-wsa+renesas@sang-engineering.com> <20170718102339.28726-4-wsa+renesas@sang-engineering.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170718102339.28726-4-wsa+renesas@sang-engineering.com> Sender: linux-media-owner@vger.kernel.org List-ID: Hi Wolfram, On 2017-07-18 12:23:38 +0200, Wolfram Sang wrote: > This ensures that we fall back to PIO if the buffer is too small for DMA > being useful. Otherwise, we use DMA. A bounce buffer might be applied if > the original message buffer is not DMA safe > > Signed-off-by: Wolfram Sang > --- > drivers/i2c/busses/i2c-sh_mobile.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-sh_mobile.c b/drivers/i2c/busses/i2c-sh_mobile.c > index 2e097d97d258bc..19f45bcd9b35ca 100644 > --- a/drivers/i2c/busses/i2c-sh_mobile.c > +++ b/drivers/i2c/busses/i2c-sh_mobile.c > @@ -145,6 +145,7 @@ struct sh_mobile_i2c_data { > struct dma_chan *dma_rx; > struct scatterlist sg; > enum dma_data_direction dma_direction; > + u8 *bounce_buf; > }; > > struct sh_mobile_dt_config { > @@ -548,6 +549,8 @@ static void sh_mobile_i2c_dma_callback(void *data) > pd->pos = pd->msg->len; > pd->stop_after_dma = true; > > + i2c_release_dma_bounce_buf(pd->msg, pd->bounce_buf); > + > iic_set_clr(pd, ICIC, 0, ICIC_TDMAE | ICIC_RDMAE); > } > > @@ -595,6 +598,7 @@ static void sh_mobile_i2c_xfer_dma(struct sh_mobile_i2c_data *pd) > struct dma_async_tx_descriptor *txdesc; > dma_addr_t dma_addr; > dma_cookie_t cookie; > + u8 *dma_buf = pd->bounce_buf ?: pd->msg->buf; This looked funny and I had to look it up, I learnt something new today :-) > > if (PTR_ERR(chan) == -EPROBE_DEFER) { > if (read) > @@ -608,7 +612,7 @@ static void sh_mobile_i2c_xfer_dma(struct sh_mobile_i2c_data *pd) > if (IS_ERR(chan)) > return; > > - dma_addr = dma_map_single(chan->device->dev, pd->msg->buf, pd->msg->len, dir); > + dma_addr = dma_map_single(chan->device->dev, dma_buf, pd->msg->len, dir); > if (dma_mapping_error(chan->device->dev, dma_addr)) { > dev_dbg(pd->dev, "dma map failed, using PIO\n"); > return; > @@ -665,7 +669,7 @@ static int start_ch(struct sh_mobile_i2c_data *pd, struct i2c_msg *usr_msg, > pd->pos = -1; > pd->sr = 0; > > - if (pd->msg->len > 8) > + if (i2c_check_msg_for_dma(pd->msg, 8, &pd->bounce_buf) == 0) Maybe the 8 should be declared in a define to explain the value, like you do in patch 4/4? This nitpick aside: Reviewed-by: Niklas Söderlund > sh_mobile_i2c_xfer_dma(pd); > > /* Enable all interrupts to begin with */ > -- > 2.11.0 > -- Regards, Niklas Söderlund