Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933973AbbEMLQe (ORCPT ); Wed, 13 May 2015 07:16:34 -0400 Received: from mail-wi0-f182.google.com ([209.85.212.182]:38275 "EHLO mail-wi0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933781AbbEMLQa (ORCPT ); Wed, 13 May 2015 07:16:30 -0400 Date: Wed, 13 May 2015 12:16:25 +0100 From: Lee Jones To: Javier Martinez Canillas Cc: Samuel Ortiz , Olof Johansson , Doug Anderson , Bill Richardson , Simon Glass , Gwendal Grignou , Stephen Barber , Filipe Brandenburger , Todd Broch , Alexandru M Stan , Heiko Stuebner , linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Zhong Subject: Re: [PATCH v2 10/10] mfd: cros_ec: spi: Add delay for asserting CS Message-ID: <20150513111625.GI3394@x1> References: <1431166241-15775-1-git-send-email-javier.martinez@collabora.co.uk> <1431166241-15775-11-git-send-email-javier.martinez@collabora.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1431166241-15775-11-git-send-email-javier.martinez@collabora.co.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4612 Lines: 117 On Sat, 09 May 2015, Javier Martinez Canillas wrote: > From: Alexandru M Stan > > Some ECs need a little time for waking up before they can accept > SPI data at a high speed. This is configurable via a DT property > "google,cros-ec-spi-pre-delay". > > If this property isn't set, then no delay will be added. However, > if set it will cause a delay equal to the value passed to it to > be inserted at the beginning of a transaction. > > Signed-off-by: Alexandru M Stan > Reviewed-by: Doug Anderson > Signed-off-by: Chris Zhong > Signed-off-by: Javier Martinez Canillas > --- > > Changes since v1: None, new patch > --- > Documentation/devicetree/bindings/mfd/cros-ec.txt | 4 ++++ > drivers/mfd/cros_ec_spi.c | 21 +++++++++++++++++++-- > 2 files changed, 23 insertions(+), 2 deletions(-) Acked-by: Lee Jones > diff --git a/Documentation/devicetree/bindings/mfd/cros-ec.txt b/Documentation/devicetree/bindings/mfd/cros-ec.txt > index 8009c3d87f33..1777916e9e28 100644 > --- a/Documentation/devicetree/bindings/mfd/cros-ec.txt > +++ b/Documentation/devicetree/bindings/mfd/cros-ec.txt > @@ -18,6 +18,10 @@ Required properties (SPI): > - reg: SPI chip select > > Optional properties (SPI): > +- google,cros-ec-spi-pre-delay: Some implementations of the EC need a little > + time to wake up from sleep before they can receive SPI transfers at a high > + clock rate. This property specifies the delay, in usecs, between the > + assertion of the CS to the start of the first clock pulse. > - google,cros-ec-spi-msg-delay: Some implementations of the EC require some > additional processing time in order to accept new transactions. If the delay > between transactions is not long enough the EC may not be able to respond > diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c > index faba03e2f1ef..16f228dc243f 100644 > --- a/drivers/mfd/cros_ec_spi.c > +++ b/drivers/mfd/cros_ec_spi.c > @@ -71,12 +71,15 @@ > * @spi: SPI device we are connected to > * @last_transfer_ns: time that we last finished a transfer, or 0 if there > * if no record > + * @start_of_msg_delay: used to set the delay_usecs on the spi_transfer that > + * is sent when we want to turn on CS at the start of a transaction. > * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that > * is sent when we want to turn off CS at the end of a transaction. > */ > struct cros_ec_spi { > struct spi_device *spi; > s64 last_transfer_ns; > + unsigned int start_of_msg_delay; > unsigned int end_of_msg_delay; > }; > > @@ -366,7 +369,7 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev, > struct ec_host_request *request; > struct ec_host_response *response; > struct cros_ec_spi *ec_spi = ec_dev->priv; > - struct spi_transfer trans; > + struct spi_transfer trans, trans_delay; > struct spi_message msg; > int i, len; > u8 *ptr; > @@ -393,13 +396,23 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev, > goto exit; > } > > + /* > + * Leave a gap between CS assertion and clocking of data to allow the > + * EC time to wakeup. > + */ > + spi_message_init(&msg); > + if (ec_spi->start_of_msg_delay) { > + memset(&trans_delay, 0, sizeof(trans_delay)); > + trans_delay.delay_usecs = ec_spi->start_of_msg_delay; > + spi_message_add_tail(&trans_delay, &msg); > + } > + > /* Transmit phase - send our message */ > memset(&trans, 0, sizeof(trans)); > trans.tx_buf = ec_dev->dout; > trans.rx_buf = rx_buf; > trans.len = len; > trans.cs_change = 1; > - spi_message_init(&msg); > spi_message_add_tail(&trans, &msg); > ret = spi_sync(ec_spi->spi, &msg); > > @@ -602,6 +615,10 @@ static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev) > u32 val; > int ret; > > + ret = of_property_read_u32(np, "google,cros-ec-spi-pre-delay", &val); > + if (!ret) > + ec_spi->start_of_msg_delay = val; > + > ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val); > if (!ret) > ec_spi->end_of_msg_delay = val; -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/