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Commit 3c4344e1 authored by Shrey Vijay's avatar Shrey Vijay
Browse files

i2c-msm-v2: Replace HW recovery mechanism with SW bit-banging 



HW recovery mechanism may not function as expected when HW samples
data line and finds it low during particular clocking period of the
recovery. Use SW bit-banging instead where SW generates clocks and
sniffs data line until data line is released by the slave.

Change-Id: I1a8b7930f256e0ff89f70b5267ee9d277c37bc42
Signed-off-by: default avatarSagar Dharia <sdharia@codeaurora.org>
Signed-off-by: default avatarShrey Vijay <shreyv@codeaurora.org>
parent a6ff4b8a

Documentation/devicetree/bindings/i2c/i2c-msm-v2.txt

+4 −0
Original line number Diff line number Diff line
@@ -16,6 +16,8 @@ Required properties: 
 - dma-names :  dma channel names.

 - qcom,clk-freq-out : Desired I2C bus clock frequency in Hz

 - qcom,clk-freq-in  : Supplied core clock frequency in Hz.

 - qcom,i2c-dat : specifies GPIO which corresponds to the I2C data line.

 - qcom,i2c-clk : specifies GPIO which corresponds to the I2C clock line.



Required alias:

 - The desired bus-number is specified by an alias with the following format:
@@ -51,5 +53,7 @@ Example: 
		qcom,clk-freq-in  = <24000000>;

		qcom,noise-rjct-scl = <0>;

		qcom,noise-rjct-sda = <0>;

		qcom,i2c-dat = <&tlmm 67 0x00>;

		qcom,i2c-clk = <&tlmm 68 0x00>;



	};

drivers/i2c/busses/i2c-msm-v2.c

+64 −48
Original line number Diff line number Diff line
@@ -32,6 +32,8 @@ 
#include <linux/dma-mapping.h>

#include <linux/i2c.h>

#include <linux/of.h>

#include <linux/gpio.h>

#include <linux/of_gpio.h>

#include <linux/msm-sps.h>

#include <linux/msm-bus.h>

#include <linux/msm-bus-board.h>
@@ -50,6 +52,9 @@ static int i2c_msm_xfer_wait_for_completion(struct i2c_msm_ctrl *ctrl, 
static int  i2c_msm_pm_resume(struct device *dev);

static void i2c_msm_pm_suspend(struct device *dev);

static void i2c_msm_clk_path_init(struct i2c_msm_ctrl *ctrl);

static struct pinctrl_state *

	i2c_msm_rsrcs_gpio_get_state(struct i2c_msm_ctrl *ctrl,

					const char *name);

static void i2c_msm_pm_pinctrl_state(struct i2c_msm_ctrl *ctrl,

						bool runtime_active);
@@ -1917,63 +1922,74 @@ static void i2c_msm_qup_init(struct i2c_msm_ctrl *ctrl) 
			"error on verifying HW support (I2C_MAST_GEN=0)\n");

}



/*

 * qup_i2c_try_recover_bus_busy: issue QUP bus clear command

 */

static int qup_i2c_try_recover_bus_busy(struct i2c_msm_ctrl *ctrl)

static void qup_i2c_recover_bit_bang(struct i2c_msm_ctrl *ctrl)

{

	int ret;

	ulong min_sleep_usec;

	int i, ret;

	int gpio_clk;

	int gpio_dat;

	bool gpio_clk_status = false;

	uint32_t status = readl_relaxed(ctrl->rsrcs.base + QUP_I2C_STATUS);

	struct pinctrl_state *bitbang;



	/* call i2c_msm_qup_init() to set core in idle state */

	i2c_msm_qup_init(ctrl);



	/* must be in run state for bus clear */

	ret = i2c_msm_qup_state_set(ctrl, QUP_STATE_RUN);

	if (ret < 0) {

		dev_err(ctrl->dev, "error: bus clear fail to set run state\n");

		return ret;

	dev_info(ctrl->dev, "Executing bus recovery procedure (9 clk pulse)\n");

	disable_irq(ctrl->rsrcs.irq);

	if (!(status & (I2C_STATUS_BUS_ACTIVE)) ||

		(status & (I2C_STATUS_BUS_MASTER))) {

		dev_warn(ctrl->dev, "unexpected i2c recovery call:0x%x\n",

				    status);

		goto recovery_exit;

	}



	/*

	 * call i2c_msm_qup_xfer_init_run_state() to set clock dividers.

	 * the dividers are necessary for bus clear.

	 */

	i2c_msm_qup_xfer_init_run_state(ctrl);



	writel_relaxed(0x1, ctrl->rsrcs.base + QUP_I2C_MASTER_BUS_CLR);

	gpio_clk = of_get_named_gpio(ctrl->adapter.dev.of_node, "qcom,i2c-clk",

				     0);

	gpio_dat = of_get_named_gpio(ctrl->adapter.dev.of_node, "qcom,i2c-dat",

				     0);



	/*

	 * wait for recovery (9 clock pulse cycles) to complete.

	 * min_time = 9 clock *10  (1000% margin)

	 * max_time = 10* min_time

	 */

	min_sleep_usec =

	  max_t(ulong, (9 * 10 * USEC_PER_SEC) / ctrl->rsrcs.clk_freq_out, 100);

	if (gpio_clk < 0 || gpio_dat < 0) {

		dev_warn(ctrl->dev, "SW bigbang err: i2c gpios not known\n");

		goto recovery_exit;

	}



	usleep_range(min_sleep_usec, min_sleep_usec * 10);

	return ret;

	bitbang = i2c_msm_rsrcs_gpio_get_state(ctrl, "i2c_bitbang");

	if (bitbang)

		ret = pinctrl_select_state(ctrl->rsrcs.pinctrl, bitbang);

	if (!bitbang || ret) {

		dev_err(ctrl->dev, "GPIO pins have no bitbang setting\n");

		goto recovery_exit;

	}

	for (i = 0; i < 10; i++) {

		if (gpio_get_value(gpio_dat) && gpio_clk_status)

			break;

		gpio_direction_output(gpio_clk, 0);

		udelay(5);

		gpio_direction_output(gpio_dat, 0);

		udelay(5);

		gpio_direction_input(gpio_clk);

		udelay(5);

		if (!gpio_get_value(gpio_clk))

			udelay(20);

		if (!gpio_get_value(gpio_clk))

			usleep_range(10000, 10001);

		gpio_clk_status = gpio_get_value(gpio_clk);

		gpio_direction_input(gpio_dat);

		udelay(5);

	}



static int qup_i2c_recover_bus_busy(struct i2c_msm_ctrl *ctrl)

{

	u32 bus_clr, bus_active, status;

	int retry = 0;

	dev_info(ctrl->dev, "Executing bus recovery procedure (9 clk pulse)\n");

	i2c_msm_pm_pinctrl_state(ctrl, true);

	udelay(10);



	do {

		qup_i2c_try_recover_bus_busy(ctrl);

		bus_clr    = readl_relaxed(ctrl->rsrcs.base +

							QUP_I2C_MASTER_BUS_CLR);

	status = readl_relaxed(ctrl->rsrcs.base + QUP_I2C_STATUS);

		bus_active = status & I2C_STATUS_BUS_ACTIVE;

		if (++retry >= I2C_QUP_MAX_BUS_RECOVERY_RETRY)

			break;

	} while (bus_clr || bus_active);

	if (!(status & I2C_STATUS_BUS_ACTIVE)) {

		dev_info(ctrl->dev,

			"Bus busy cleared after %d clock cycles, status %x\n",

			 i, status);

		goto recovery_exit;

	}



	dev_info(ctrl->dev, "Bus recovery %s after %d retries\n",

		(bus_clr || bus_active) ? "fail" : "success", retry);

	return 0;

	dev_warn(ctrl->dev, "Bus still busy, status %x\n", status);



recovery_exit:

	enable_irq(ctrl->rsrcs.irq);

}



static int i2c_msm_qup_post_xfer(struct i2c_msm_ctrl *ctrl, int err)
@@ -1984,7 +2000,7 @@ static int i2c_msm_qup_post_xfer(struct i2c_msm_ctrl *ctrl, int err) 
		    (ctrl->xfer.err == I2C_MSM_ERR_BUS_ERR)  ||

		    (ctrl->xfer.err == I2C_MSM_ERR_TIMEOUT)) {

			if (i2c_msm_qup_slv_holds_bus(ctrl))

				qup_i2c_recover_bus_busy(ctrl);

				qup_i2c_recover_bit_bang(ctrl);



			/* do not generalize error to EIO if its already set */

			if (!err)

include/linux/i2c/i2c-msm-v2.h

+1 −2
Original line number Diff line number Diff line 
/* Copyright (c) 2014-2015,2017, The Linux Foundation. All rights reserved.

/* Copyright (c) 2014-2015,2017-2018, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and
@@ -201,7 +201,6 @@ enum i2c_msm_power_state { 
#define I2C_MSM_MAX_POLL_MSEC           (100)

#define I2C_MSM_TIMEOUT_SAFTY_COEF      (10)

#define I2C_MSM_TIMEOUT_MIN_USEC        (500000)

#define I2C_QUP_MAX_BUS_RECOVERY_RETRY  (10)



/* QUP v2 tags */

#define QUP_TAG2_DATA_WRITE        (0x82ULL)