Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752002AbbLNB3o (ORCPT ); Sun, 13 Dec 2015 20:29:44 -0500 Received: from mail.kernel.org ([198.145.29.136]:48978 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751611AbbLNB3n (ORCPT ); Sun, 13 Dec 2015 20:29:43 -0500 Date: Sun, 13 Dec 2015 19:29:37 -0600 From: Rob Herring To: Marcus Weseloh Cc: linux-sunxi@googlegroups.com, Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Mark Brown , Maxime Ripard , Chen-Yu Tsai , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v3] spi: dts: sun4i: Add support for hardware-based wait time between words Message-ID: <20151214012937.GA12209@rob-hp-laptop> References: <1449873940-10167-1-git-send-email-mweseloh42@gmail.com> <1450047853-9005-1-git-send-email-mweseloh42@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1450047853-9005-1-git-send-email-mweseloh42@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3835 Lines: 99 On Mon, Dec 14, 2015 at 12:04:11AM +0100, Marcus Weseloh wrote: > Adds a new property "spi-word-wait-ns" to the spi-bus binding that allows > SPI slave devices to set a hardware based wait time between the > transmission of words. Also modifies the sun4i SPI master driver to make > use of the new property. This specific SPI controller needs 3 clock > cycles to set up the delay, which makes the minimum non-zero wait time > on this hardware 4 clock cycles. > > Signed-off-by: Marcus Weseloh > --- > Changes from v1: > * renamed the property for more clarity > * wait time is set in nanoseconds instead of number of clock cycles > * transparently handle the 3 setup clock cycles > > Changes from v2: > * fixed typo in comment > * moved parameter to spi-bus binding, dropping the vendor prefix > * changed commit summary and description to reflect the changes > --- > Documentation/devicetree/bindings/spi/spi-bus.txt | 2 ++ > drivers/spi/spi-sun4i.c | 23 +++++++++++++++++++++++ > 2 files changed, 25 insertions(+) > > diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt > index bbaa857..2d6034f 100644 > --- a/Documentation/devicetree/bindings/spi/spi-bus.txt > +++ b/Documentation/devicetree/bindings/spi/spi-bus.txt > @@ -61,6 +61,8 @@ contain the following properties. > used for MOSI. Defaults to 1 if not present. > - spi-rx-bus-width - (optional) The bus width(number of data wires) that > used for MISO. Defaults to 1 if not present. > +- spi-word-wait-ns - (optional) Hardware based delay between transmission of > + words in nanoseconds Could be a software delay if the h/w doesn't support delays. > Some SPI controllers and devices support Dual and Quad SPI transfer mode. > It allows data in the SPI system to be transferred in 2 wires(DUAL) or 4 wires(QUAD). > diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c > index f60a6d6..73995a1 100644 > --- a/drivers/spi/spi-sun4i.c > +++ b/drivers/spi/spi-sun4i.c > @@ -19,6 +19,7 @@ > #include > #include > #include > +#include > > #include > > @@ -173,6 +174,9 @@ static int sun4i_spi_transfer_one(struct spi_master *master, > unsigned int tx_len = 0; > int ret = 0; > u32 reg; > + u32 wait_ns = 0; > + int wait_clk = 0; > + int clk_ns = 0; > > /* We don't support transfer larger than the FIFO */ > if (tfr->len > SUN4I_FIFO_DEPTH) > @@ -261,6 +265,25 @@ static int sun4i_spi_transfer_one(struct spi_master *master, > > sun4i_spi_write(sspi, SUN4I_CLK_CTL_REG, reg); > > + /* Setup wait time between words */ > + of_property_read_u32(spi->dev.of_node, "spi-word-wait-ns", > + &wait_ns); Read this in probe and save the value rather than fetching every transfer. > + if (wait_ns) { > + /* The wait time is set in SPI_CLK cycles. The SPI hardware > + * needs 3 additional cycles to setup the wait counter, so > + * the minimum delay time is 4 cycles. > + */ > + clk_ns = DIV_ROUND_UP(1000000000, tfr->speed_hz); > + wait_clk = DIV_ROUND_UP(wait_ns, clk_ns) - 3; > + if (wait_clk < 1) { > + wait_clk = 1; > + dev_info(&spi->dev, > + "using minimum of 4 word wait cycles (%uns)", > + 4 * clk_ns); > + } > + } > + sun4i_spi_write(sspi, SUN4I_WAIT_REG, (u16)wait_clk); > + > /* Setup the transfer now... */ > if (sspi->tx_buf) > tx_len = tfr->len; > -- > 1.9.1 > -- 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/