From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.89 #1 (Red Hat Linux)) id 1eZY2f-0002hl-ND for barebox@lists.infradead.org; Thu, 11 Jan 2018 08:16:56 +0000 Date: Thu, 11 Jan 2018 09:16:41 +0100 From: Sascha Hauer Message-ID: <20180111081641.wqec5kqjhqsgwpay@pengutronix.de> References: <20180110075202.4867-1-s.trumtrar@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20180110075202.4867-1-s.trumtrar@pengutronix.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH] i2c: designware: evaluate i2c-sda-hold-time property To: Steffen Trumtrar Cc: barebox@lists.infradead.org On Wed, Jan 10, 2018 at 08:52:02AM +0100, Steffen Trumtrar wrote: > Newer designware i2c controllers allow setting the SDA hold time. > Evaluate the devicetree property "i2c-sda-hold-time" and set the > value accordingly. > The code is an adaption of the Linux v4.12 driver. > > Signed-off-by: Steffen Trumtrar > --- > drivers/i2c/busses/i2c-designware.c | 40 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) Applied, thanks Sascha > > diff --git a/drivers/i2c/busses/i2c-designware.c b/drivers/i2c/busses/i2c-designware.c > index 0b022afd30f8..33f89148f0cc 100644 > --- a/drivers/i2c/busses/i2c-designware.c > +++ b/drivers/i2c/busses/i2c-designware.c > @@ -32,6 +32,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -75,6 +76,7 @@ > #define DW_IC_TX_TL 0x3c > #define DW_IC_CLR_INTR 0x40 > #define DW_IC_CLR_TX_ABRT 0x54 > +#define DW_IC_SDA_HOLD 0x7c > > #define DW_IC_ENABLE 0x6c > #define DW_IC_ENABLE_ENABLE (1 << 0) > @@ -90,6 +92,8 @@ > #define DW_IC_ENABLE_STATUS 0x9c > #define DW_IC_ENABLE_STATUS_IC_EN (1 << 0) > > +#define DW_IC_COMP_VERSION 0xf8 > +#define DW_IC_SDA_HOLD_MIN_VERS 0x3131312A > #define DW_IC_COMP_TYPE 0xfc > #define DW_IC_COMP_TYPE_VALUE 0x44570140 > > @@ -99,10 +103,15 @@ > #define DW_TIMEOUT_TX (2 * MSECOND) > #define DW_TIMEOUT_RX (2 * MSECOND) > > +#define DW_IC_SDA_HOLD_RX_SHIFT 16 > +#define DW_IC_SDA_HOLD_RX_MASK GENMASK(23, DW_IC_SDA_HOLD_RX_SHIFT) > + > + > struct dw_i2c_dev { > void __iomem *base; > struct clk *clk; > struct i2c_adapter adapter; > + u32 sda_hold_time; > }; > > static inline struct dw_i2c_dev *to_dw_i2c_dev(struct i2c_adapter *a) > @@ -202,6 +211,7 @@ i2c_dw_scl_lcnt(uint32_t ic_clk, uint32_t tLOW, uint32_t tf, int offset) > static void i2c_dw_setup_timings(struct dw_i2c_dev *dw) > { > uint32_t hcnt, lcnt; > + u32 reg; > > const uint32_t sda_falling_time = 300; /* ns */ > const uint32_t scl_falling_time = 300; /* ns */ > @@ -234,6 +244,36 @@ static void i2c_dw_setup_timings(struct dw_i2c_dev *dw) > > writel(hcnt, dw->base + DW_IC_FS_SCL_HCNT); > writel(lcnt, dw->base + DW_IC_FS_SCL_LCNT); > + > + /* Configure SDA Hold Time if required */ > + reg = readl(dw->base + DW_IC_COMP_VERSION); > + if (reg >= DW_IC_SDA_HOLD_MIN_VERS) { > + u32 ht; > + int ret; > + > + ret = of_property_read_u32(dw->adapter.dev.device_node, > + "i2c-sda-hold-time-ns", &ht); > + if (ret) { > + /* Keep previous hold time setting if no one set it */ > + dw->sda_hold_time = readl(dw->base + DW_IC_SDA_HOLD); > + } else if (ht) { > + dw->sda_hold_time = div_u64((u64)input_clock_khz * ht + 500000, > + 1000000); > + } > + > + /* > + * Workaround for avoiding TX arbitration lost in case I2C > + * slave pulls SDA down "too quickly" after falling egde of > + * SCL by enabling non-zero SDA RX hold. Specification says it > + * extends incoming SDA low to high transition while SCL is > + * high but it apprears to help also above issue. > + */ > + if (!(dw->sda_hold_time & DW_IC_SDA_HOLD_RX_MASK)) > + dw->sda_hold_time |= 1 << DW_IC_SDA_HOLD_RX_SHIFT; > + > + dev_dbg(&dw->adapter.dev, "adjust SDA hold time.\n"); > + writel(dw->sda_hold_time, dw->base + DW_IC_SDA_HOLD); > + } > } > > static int i2c_dw_wait_for_bits(struct dw_i2c_dev *dw, uint32_t offset, > -- > 2.11.0 > > > _______________________________________________ > barebox mailing list > barebox@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/barebox > -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox