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Thu, 02 Apr 2026 07:19:36 -0700 (PDT) Received: from rockpi-5b ([45.112.0.200]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35dbe9377b7sm10959123a91.10.2026.04.02.07.19.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2026 07:19:35 -0700 (PDT) From: Anand Moon To: Heiko Stuebner , Andi Shyti , linux-arm-kernel@lists.infradead.org (moderated list:ARM/Rockchip SoC support), linux-rockchip@lists.infradead.org (open list:ARM/Rockchip SoC support), linux-i2c@vger.kernel.org (open list:I2C SUBSYSTEM HOST DRIVERS), linux-kernel@vger.kernel.org (open list) Cc: Anand Moon , David Wu Subject: [PATCH v3 1/2] i2c: rk3x: add support for SCL OE debounce and slave hold recovery Date: Thu, 2 Apr 2026 19:49:22 +0530 Message-ID: <20260402141927.7216-1-linux.amoon@gmail.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: David Wu As per the RK3399 and RK35xx datasheet, Rockchip I2C controllers feature a SCL_OE_DB register (0x24). This register is used to configure the debounce time for the SCL output enable signal, which helps prevent glitches and ensures timing compliance during bus handover or slave clock stretching. Introduce a 'has_scl_oe_debounce' flag to rk3x_i2c_soc_data to distinguish between hardware versions. For supported SoCs, calculate the debounce counter dynamically based on the current clock rate and program it during divider adaptation. Additionally: - Implement detection for the REG_INT_SLV_HDSCL (Slave Hold SCL) interrupt bit during transfer timeouts. - Capture the Interrupt Pending (IPD) register state before clearing interrupts during a timeout to check for the slave hold condition. - Re-apply the clock dividers via rk3x_i2c_adapt_div() if a slave hold is detected on supported SoCs to attempt bus recovery. - Initialize the SLV_HDSCL bit in i2c_start for I2C interrupt field. The recovery logic is gated by 'has_scl_oe_debounce' to ensure that reserved bits on older SoC variants do not trigger false-positive recoveries. Signed-off-by: David Wu Signed-off-by: Anand Moon --- Changes: v3: intialize the SLV_HDSCL bit in in i2c_start for interupt enable v2: https://lore.kernel.org/all/20260321105146.7419-1-linux.amoon@gmail.com/ v2: Aded the to detect REG_INT_SLV_HDSCL interrupt timeout it was part of origmal commit below. [1] https://github.com/radxa/kernel/commit/006c0b1e7710d471119a69d6bd56917a15a85a0b Fix the order of SoB, Fix the doc warning reporteed by kernel test robot v1: https://lore.kernel.org/all/20260103052506.6743-1-linux.amoon@gmail.com/ --- drivers/i2c/busses/i2c-rk3x.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c index fcede9f6ed54..06a77780cf82 100644 --- a/drivers/i2c/busses/i2c-rk3x.c +++ b/drivers/i2c/busses/i2c-rk3x.c @@ -36,6 +36,7 @@ #define REG_IEN 0x18 /* interrupt enable */ #define REG_IPD 0x1c /* interrupt pending */ #define REG_FCNT 0x20 /* finished count */ +#define REG_SCL_OE_DB 0x24 /* Slave hold scl debounce */ /* Data buffer offsets */ #define TXBUFFER_BASE 0x100 @@ -74,6 +75,7 @@ enum { #define REG_INT_START BIT(4) /* START condition generated */ #define REG_INT_STOP BIT(5) /* STOP condition generated */ #define REG_INT_NAKRCV BIT(6) /* NACK received */ +#define REG_INT_SLV_HDSCL BIT(7) /* Slave hold scl interrupt enable */ #define REG_INT_ALL 0x7f /* Constants */ @@ -161,10 +163,12 @@ enum rk3x_i2c_state { /** * struct rk3x_i2c_soc_data - SOC-specific data + * @has_scl_oe_debounce: Support for slave hold SCL debounce * @grf_offset: offset inside the grf regmap for setting the i2c type * @calc_timings: Callback function for i2c timing information calculated */ struct rk3x_i2c_soc_data { + bool has_scl_oe_debounce; int grf_offset; int (*calc_timings)(unsigned long, struct i2c_timings *, struct rk3x_i2c_calced_timings *); @@ -248,8 +252,12 @@ static inline void rk3x_i2c_clean_ipd(struct rk3x_i2c *i2c) static void rk3x_i2c_start(struct rk3x_i2c *i2c) { u32 val = i2c_readl(i2c, REG_CON) & REG_CON_TUNING_MASK; + u32 ien = REG_INT_START; - i2c_writel(i2c, REG_INT_START, REG_IEN); + if (i2c->soc_data->has_scl_oe_debounce) + ien |= REG_INT_SLV_HDSCL; + + i2c_writel(i2c, ien, REG_IEN); /* enable adapter with correct mode, send START condition */ val |= REG_CON_EN | REG_CON_MOD(i2c->mode) | REG_CON_START; @@ -876,6 +884,7 @@ static void rk3x_i2c_adapt_div(struct rk3x_i2c *i2c, unsigned long clk_rate) { struct i2c_timings *t = &i2c->t; struct rk3x_i2c_calced_timings calc; + unsigned long period, time_hold = (WAIT_TIMEOUT / 2) * 1000000; u64 t_low_ns, t_high_ns; unsigned long flags; u32 val; @@ -893,6 +902,13 @@ static void rk3x_i2c_adapt_div(struct rk3x_i2c *i2c, unsigned long clk_rate) i2c_writel(i2c, val, REG_CON); i2c_writel(i2c, (calc.div_high << 16) | (calc.div_low & 0xffff), REG_CLKDIV); + + if (i2c->soc_data->has_scl_oe_debounce) { + period = DIV_ROUND_UP(1000000000, clk_rate); + val = DIV_ROUND_UP(time_hold, period); + i2c_writel(i2c, val, REG_SCL_OE_DB); + } + spin_unlock_irqrestore(&i2c->lock, flags); clk_disable(i2c->pclk); @@ -1063,6 +1079,7 @@ static int rk3x_i2c_xfer_common(struct i2c_adapter *adap, unsigned long flags; long time_left; u32 val; + u32 ipd = 0; /* To store interrupt pending status for timeout analysis */ int ret = 0; int i; @@ -1107,6 +1124,9 @@ static int rk3x_i2c_xfer_common(struct i2c_adapter *adap, spin_lock_irqsave(&i2c->lock, flags); if (time_left == 0) { + /* Read IPD before clearing to check for Slave Hold SCL */ + ipd = i2c_readl(i2c, REG_IPD); + /* Force a STOP condition without interrupt */ i2c_writel(i2c, 0, REG_IEN); val = i2c_readl(i2c, REG_CON) & REG_CON_TUNING_MASK; @@ -1125,6 +1145,17 @@ static int rk3x_i2c_xfer_common(struct i2c_adapter *adap, } } + /* + * If a timeout occurred and the slave is holding SCL, + * re-apply the timings/dividers to attempt recovery. + */ + if (ret == -ETIMEDOUT && i2c->soc_data->has_scl_oe_debounce) { + if (ipd & REG_INT_SLV_HDSCL) { + dev_err(i2c->dev, "SCL hold by slave detected, resetting timings.\n"); + rk3x_i2c_adapt_div(i2c, clk_get_rate(i2c->clk)); + } + } + clk_disable(i2c->pclk); clk_disable(i2c->clk); @@ -1198,6 +1229,7 @@ static const struct rk3x_i2c_soc_data rk3288_soc_data = { static const struct rk3x_i2c_soc_data rk3399_soc_data = { .grf_offset = -1, .calc_timings = rk3x_i2c_v1_calc_timings, + .has_scl_oe_debounce = true, }; static const struct of_device_id rk3x_i2c_match[] = { base-commit: 9147566d801602c9e7fc7f85e989735735bf38ba -- 2.50.1