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[209.132.180.67]) by mx.google.com with ESMTP id e65si16095518pgc.454.2019.06.26.11.34.56; Wed, 26 Jun 2019 11:35:13 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726553AbfFZSel (ORCPT + 99 others); Wed, 26 Jun 2019 14:34:41 -0400 Received: from saturn.retrosnub.co.uk ([46.235.226.198]:35684 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726425AbfFZSel (ORCPT ); Wed, 26 Jun 2019 14:34:41 -0400 Received: from archlinux (cpc149474-cmbg20-2-0-cust94.5-4.cable.virginm.net [82.4.196.95]) by saturn.retrosnub.co.uk (Postfix; Retrosnub mail submission) with ESMTPSA id 78A019E73B6; Wed, 26 Jun 2019 19:34:39 +0100 (BST) Date: Wed, 26 Jun 2019 19:34:38 +0100 From: Jonathan Cameron To: Alexandru Ardelean Cc: , , , , Michael Hennerich , Mark Brown Subject: Re: [PATCH 2/5] drivers: spi: core: Add optional stall delay between cs_change transfers Message-ID: <20190626193438.7248d0a9@archlinux> In-Reply-To: <20190625131328.11883-2-alexandru.ardelean@analog.com> References: <20190625131328.11883-1-alexandru.ardelean@analog.com> <20190625131328.11883-2-alexandru.ardelean@analog.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 25 Jun 2019 16:13:25 +0300 Alexandru Ardelean wrote: > Some devices like the ADIS16460 IMU require a stall period between > transfers, i.e. between when the CS is de-asserted and re-asserted. The > default value of 10us is not enough. This change makes the delay > configurable for when the next CS change goes active. > > Signed-off-by: Michael Hennerich > Signed-off-by: Alexandru Ardelean General principle seems fine to me, though naming may need some work. cs_low_time or something more specific than stall perhaps? +CC Mark. > --- > drivers/spi/spi.c | 3 ++- > include/linux/spi/spi.h | 3 +++ > 2 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c > index 5e75944ad5d1..739de0118ee1 100644 > --- a/drivers/spi/spi.c > +++ b/drivers/spi/spi.c > @@ -1163,7 +1163,8 @@ static int spi_transfer_one_message(struct spi_controller *ctlr, > keep_cs = true; > } else { > spi_set_cs(msg->spi, false); > - udelay(10); > + udelay(xfer->cs_change_stall_delay_us ? > + xfer->cs_change_stall_delay_us : 10); > spi_set_cs(msg->spi, true); > } > } > diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h > index 053abd22ad31..d23add3b4790 100644 > --- a/include/linux/spi/spi.h > +++ b/include/linux/spi/spi.h > @@ -734,6 +734,8 @@ extern void spi_res_release(struct spi_controller *ctlr, > * transfer. If 0 the default (from @spi_device) is used. > * @bits_per_word: select a bits_per_word other than the device default > * for this transfer. If 0 the default (from @spi_device) is used. > + * @cs_change_stall_delay_us: microseconds to delay between cs_change > + * transfers. > * @cs_change: affects chipselect after this transfer completes > * @delay_usecs: microseconds to delay after this transfer before > * (optionally) changing the chipselect status, then starting > @@ -823,6 +825,7 @@ struct spi_transfer { > #define SPI_NBITS_QUAD 0x04 /* 4bits transfer */ > u8 bits_per_word; > u8 word_delay_usecs; > + u8 cs_change_stall_delay_us; > u16 delay_usecs; > u32 speed_hz; > u16 word_delay;