From patchwork Thu Dec 27 09:42:24 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gabor Juhos X-Patchwork-Id: 1912591 Return-Path: X-Original-To: patchwork-spi-devel-general@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork2.kernel.org Received: from lists.sourceforge.net (lists.sourceforge.net [216.34.181.88]) by patchwork2.kernel.org (Postfix) with ESMTP id 8DFE0DF2A2 for ; Thu, 27 Dec 2012 09:59:02 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=sfs-ml-3.v29.ch3.sourceforge.com) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1ToAEu-00086c-Tf; Thu, 27 Dec 2012 09:59:00 +0000 Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1ToAEt-00086W-T7 for spi-devel-general@lists.sourceforge.net; Thu, 27 Dec 2012 09:58:59 +0000 X-ACL-Warn: Received: from arrakis.dune.hu ([78.24.191.176]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.76) id 1ToAEq-00014q-JQ for spi-devel-general@lists.sourceforge.net; Thu, 27 Dec 2012 09:58:59 +0000 Received: from arrakis.dune.hu ([127.0.0.1]) by localhost (arrakis.dune.hu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 8t3OtUndaZsC; Thu, 27 Dec 2012 10:41:43 +0100 (CET) Received: from localhost.localdomain (catvpool-576570d8.szarvasnet.hu [87.101.112.216]) by arrakis.dune.hu (Postfix) with ESMTPSA id 2124C280F3E; Thu, 27 Dec 2012 10:41:43 +0100 (CET) From: Gabor Juhos To: Grant Likely Subject: [PATCH 1/6] spi/ath79: add delay between SCK changes Date: Thu, 27 Dec 2012 10:42:24 +0100 Message-Id: <1356601349-23617-2-git-send-email-juhosg@openwrt.org> X-Mailer: git-send-email 1.7.10 In-Reply-To: <1356601349-23617-1-git-send-email-juhosg@openwrt.org> References: <1356601349-23617-1-git-send-email-juhosg@openwrt.org> X-Spam-Score: 0.0 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. X-Headers-End: 1ToAEq-00014q-JQ Cc: spi-devel-general@lists.sourceforge.net, Gabor Juhos X-BeenThere: spi-devel-general@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: Linux SPI core/device drivers discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: spi-devel-general-bounces@lists.sourceforge.net The driver uses the "as fast as it can" approach to drive the SCK signal. However this does not work with certain low speed SPI chips (e.g. the PCF2123 RTC chip). The patch adds per-bit slowdowns in order to be able to use the driver with such chips as well. Signed-off-by: Gabor Juhos --- drivers/spi/spi-ath79.c | 44 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 43 insertions(+), 1 deletion(-) diff --git a/drivers/spi/spi-ath79.c b/drivers/spi/spi-ath79.c index 9a5d779..e025282 100644 --- a/drivers/spi/spi-ath79.c +++ b/drivers/spi/spi-ath79.c @@ -24,17 +24,24 @@ #include #include #include +#include +#include #include #include #define DRV_NAME "ath79-spi" +#define ATH79_SPI_RRW_DELAY_FACTOR 12000 +#define MHZ (1000 * 1000) + struct ath79_spi { struct spi_bitbang bitbang; u32 ioc_base; u32 reg_ctrl; void __iomem *base; + struct clk *clk; + unsigned rrw_delay; }; static inline u32 ath79_spi_rr(struct ath79_spi *sp, unsigned reg) @@ -52,6 +59,12 @@ static inline struct ath79_spi *ath79_spidev_to_sp(struct spi_device *spi) return spi_master_get_devdata(spi->master); } +static inline void ath79_spi_delay(struct ath79_spi *sp, unsigned nsecs) +{ + if (nsecs > sp->rrw_delay) + ndelay(nsecs - sp->rrw_delay); +} + static void ath79_spi_chipselect(struct spi_device *spi, int is_active) { struct ath79_spi *sp = ath79_spidev_to_sp(spi); @@ -184,7 +197,9 @@ static u32 ath79_spi_txrx_mode0(struct spi_device *spi, unsigned nsecs, /* setup MSB (to slave) on trailing edge */ ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out); + ath79_spi_delay(sp, nsecs); ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out | AR71XX_SPI_IOC_CLK); + ath79_spi_delay(sp, nsecs); word <<= 1; } @@ -198,6 +213,7 @@ static int ath79_spi_probe(struct platform_device *pdev) struct ath79_spi *sp; struct ath79_spi_platform_data *pdata; struct resource *r; + unsigned long rate; int ret; master = spi_alloc_master(&pdev->dev, sizeof(*sp)); @@ -236,12 +252,36 @@ static int ath79_spi_probe(struct platform_device *pdev) goto err_put_master; } + sp->clk = clk_get(&pdev->dev, "ahb"); + if (IS_ERR(sp->clk)) { + ret = PTR_ERR(sp->clk); + goto err_unmap; + } + + ret = clk_enable(sp->clk); + if (ret) + goto err_clk_put; + + rate = DIV_ROUND_UP(clk_get_rate(sp->clk), MHZ); + if (!rate) { + ret = -EINVAL; + goto err_clk_disable; + } + + sp->rrw_delay = ATH79_SPI_RRW_DELAY_FACTOR / rate; + dev_dbg(&pdev->dev, "register read/write delay is %u nsecs\n", + sp->rrw_delay); + ret = spi_bitbang_start(&sp->bitbang); if (ret) - goto err_unmap; + goto err_clk_disable; return 0; +err_clk_disable: + clk_disable(sp->clk); +err_clk_put: + clk_put(sp->clk); err_unmap: iounmap(sp->base); err_put_master: @@ -256,6 +296,8 @@ static int ath79_spi_remove(struct platform_device *pdev) struct ath79_spi *sp = platform_get_drvdata(pdev); spi_bitbang_stop(&sp->bitbang); + clk_disable(sp->clk); + clk_put(sp->clk); iounmap(sp->base); platform_set_drvdata(pdev, NULL); spi_master_put(sp->bitbang.master);