Re: [PATCH V10 1/2] i2c/adapter: Add bus recovery infrastructure

[Viresh Kumar <viresh.kumar-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

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On 25 January 2013 16:43, Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> wrote:
> Code-wise I am mostly satisfied, except that I need to think about
> clock-stretching a little more. We could add that later, too.

Great!!

> However, while I understand you are keen to get rid of this series ASAP,
> it seems that this eagerness results in some sloppyness which is a bit
> cumbersome (most lines changed since last time have something to comment
> on).

:(

> So, I'll try a different review style this time and let you do the
> detective work :)
>
> 1) Please be strict and consistent with spaces around operators.

Sorry, but i couldn't find any such issues in code (but were there
in a comment)

> 2) Make sure the warnings and printouts match the code
> 3) Take the printouts serious and invest a thought if they can be
> further improved.

I have looked them again and attached are the final patches.
Following are the improvements i have:

Author: Viresh Kumar <viresh.kumar-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Date:   Sat Jan 26 10:31:42 2013 +0530

    fixup! i2c/adapter: Add bus recovery infrastructure
---
 drivers/i2c/i2c-core.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 24c8a1e..3ec040e 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -136,14 +136,14 @@ static int i2c_get_gpios_for_recovery(struct
i2c_adapter *adap)
        ret = gpio_request_one(bri->scl_gpio, GPIOF_OPEN_DRAIN |
                        GPIOF_OUT_INIT_HIGH, "i2c-scl");
        if (ret) {
-               dev_warn(dev, "gpio request fail: %d\n", bri->scl_gpio);
+               dev_warn(dev, "Can't get SCL gpio: %d\n", bri->scl_gpio);
                return ret;
        }

        if (bri->get_sda) {
                if (gpio_request_one(bri->sda_gpio, GPIOF_IN, "i2c-sda")) {
                        /* work without SDA polling */
-                       dev_warn(dev, "can't get SDA: %d. not using
SDA polling\n",
+                       dev_warn(dev, "Can't get SDA gpio: %d. Not
using SDA polling\n",
                                        bri->sda_gpio);
                        bri->get_sda = NULL;
                }
@@ -163,8 +163,11 @@ static void i2c_put_gpios_for_recovery(struct
i2c_adapter *adap)
 }

 /*
- * We need to provide delay after every half clock pulse,
- * delay in ns = (10^6/ 100 KHz)/2
+ * We are generating clock pulse. ndelay() would decide durating of clk pulse.
+ * We will generate clock with rate 100 KHz and so duration of both
clock levels
+ * would be:
+ *
+ * delay in ns = (10^6 / 100) / 2
  */
 #define RECOVERY_CLK_CNT       9
 #define RECOVERY_NDELAY                5000
@@ -181,13 +184,13 @@ static int i2c_generic_recovery(struct i2c_adapter *adap)
         */
        while (i++ < RECOVERY_CLK_CNT * 2) {
                if (val) {
-                       /* break if SDA got high */
+                       /* Break if SDA is high */
                        if (bri->get_sda && bri->get_sda(adap))
                                        break;
                        /* SCL shouldn't be low here */
                        if (!bri->get_scl(adap)) {
                                dev_err(&adap->dev,
-                                       "SCL is stuck low exit recovery\n");
+                                       "SCL is stuck low, exit recovery\n");
                                ret = -EBUSY;
                                break;
                        }
@@ -229,7 +232,7 @@ int i2c_recover_bus(struct i2c_adapter *adap)
        if (!adap->bus_recovery_info)
                return -EOPNOTSUPP;

-       dev_dbg(&adap->dev, "trying i2c bus recovery\n");
+       dev_dbg(&adap->dev, "Trying i2c bus recovery\n");
        return adap->bus_recovery_info->recover_bus(adap);
 }

@@ -1031,12 +1034,12 @@ static int i2c_register_adapter(struct
i2c_adapter *adap)
                struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;

                if (!bri->recover_bus) {
-                       dev_err(&adap->dev, "No recover_bus(), not
using recovery\n");
+                       dev_err(&adap->dev, "No recover_bus() found,
not using recovery\n");
                        adap->bus_recovery_info = NULL;
                        goto exit_recovery;
                }

-               /* GPIO recovery */
+               /* Generic GPIO recovery */
                if (bri->recover_bus == i2c_generic_gpio_recovery) {
                        if (!gpio_is_valid(bri->scl_gpio)) {
                                dev_err(&adap->dev, "Invalid SCL gpio,
not using recovery\n");
@@ -1052,8 +1055,9 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
                        bri->get_scl = get_scl_gpio_value;
                        bri->set_scl = set_scl_gpio_value;
                } else if (!bri->set_scl || !bri->get_scl) {
-                       dev_warn(&adap->dev,
-                                       "set_scl() is must for SCL recovery\n");
+                       /* Generic SCL recovery */
+                       dev_err(&adap->dev, "No get[set]_gpio() found,
not using recovery\n");
+                       adap->bus_recovery_info = NULL;
                }
        }

[-- Attachment #2: 0001-i2c-adapter-Add-bus-recovery-infrastructure.patch --]
[-- Type: application/octet-stream, Size: 8558 bytes --]

From 68f1dea5e585a7cf4d719232ff94c02aef8620e6 Mon Sep 17 00:00:00 2001
Message-Id: <68f1dea5e585a7cf4d719232ff94c02aef8620e6.1359177099.git.viresh.kumar@linaro.org>
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: Tue, 28 Feb 2012 18:26:31 +0530
Subject: [PATCH V11 1/2] i2c/adapter: Add bus recovery infrastructure

Add i2c bus recovery infrastructure to i2c adapters as specified in the i2c
protocol Rev. 03 section 3.1.16 titled "Bus clear".

http://www.nxp.com/documents/user_manual/UM10204.pdf

Sometimes during operation i2c bus hangs and we need to give dummy clocks to
slave device to start the transfer again. Now we may have capability in the bus
controller to generate these clocks or platform may have gpio pins which can be
toggled to generate dummy clocks. This patch supports both.

This patch also adds in generic bus recovery routines gpio or scl line based
which can be used by bus controller. In addition controller driver may provide
its own version of the bus recovery routine.

This doesn't support multi-master recovery for now.

Reviewed-by: Paul Carpenter <paul@pcserviceselectronics.co.uk>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/i2c/i2c-core.c | 160 +++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/i2c.h    |  40 +++++++++++++
 2 files changed, 200 insertions(+)

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index e388590..3ec040e 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -27,7 +27,9 @@
 
 #include <linux/module.h>
 #include <linux/kernel.h>
+#include <linux/delay.h>
 #include <linux/errno.h>
+#include <linux/gpio.h>
 #include <linux/slab.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
@@ -109,6 +111,131 @@ static int i2c_device_uevent(struct device *dev, struct kobj_uevent_env *env)
 #define i2c_device_uevent	NULL
 #endif	/* CONFIG_HOTPLUG */
 
+/* i2c bus recovery routines */
+static int get_scl_gpio_value(struct i2c_adapter *adap)
+{
+	return gpio_get_value(adap->bus_recovery_info->scl_gpio);
+}
+
+static void set_scl_gpio_value(struct i2c_adapter *adap, int val)
+{
+	gpio_set_value(adap->bus_recovery_info->scl_gpio, val);
+}
+
+static int get_sda_gpio_value(struct i2c_adapter *adap)
+{
+	return gpio_get_value(adap->bus_recovery_info->sda_gpio);
+}
+
+static int i2c_get_gpios_for_recovery(struct i2c_adapter *adap)
+{
+	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+	struct device *dev = &adap->dev;
+	int ret = 0;
+
+	ret = gpio_request_one(bri->scl_gpio, GPIOF_OPEN_DRAIN |
+			GPIOF_OUT_INIT_HIGH, "i2c-scl");
+	if (ret) {
+		dev_warn(dev, "Can't get SCL gpio: %d\n", bri->scl_gpio);
+		return ret;
+	}
+
+	if (bri->get_sda) {
+		if (gpio_request_one(bri->sda_gpio, GPIOF_IN, "i2c-sda")) {
+			/* work without SDA polling */
+			dev_warn(dev, "Can't get SDA gpio: %d. Not using SDA polling\n",
+					bri->sda_gpio);
+			bri->get_sda = NULL;
+		}
+	}
+
+	return ret;
+}
+
+static void i2c_put_gpios_for_recovery(struct i2c_adapter *adap)
+{
+	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+
+	if (bri->get_sda)
+		gpio_free(bri->sda_gpio);
+
+	gpio_free(bri->scl_gpio);
+}
+
+/*
+ * We are generating clock pulse. ndelay() would decide durating of clk pulse.
+ * We will generate clock with rate 100 KHz and so duration of both clock levels
+ * would be:
+ *
+ * delay in ns = (10^6 / 100) / 2
+ */
+#define RECOVERY_CLK_CNT	9
+#define RECOVERY_NDELAY		5000
+static int i2c_generic_recovery(struct i2c_adapter *adap)
+{
+	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+	int i = 0, val = 1, ret = 0;
+
+	if (bri->prepare_recovery)
+		bri->prepare_recovery(bri);
+
+	/*
+	 * By this time SCL is high, as we need to give 9 falling-rising edges
+	 */
+	while (i++ < RECOVERY_CLK_CNT * 2) {
+		if (val) {
+			/* Break if SDA is high */
+			if (bri->get_sda && bri->get_sda(adap))
+					break;
+			/* SCL shouldn't be low here */
+			if (!bri->get_scl(adap)) {
+				dev_err(&adap->dev,
+					"SCL is stuck low, exit recovery\n");
+				ret = -EBUSY;
+				break;
+			}
+		}
+
+		val = !val;
+		bri->set_scl(adap, val);
+		ndelay(RECOVERY_NDELAY);
+	}
+
+	if (bri->unprepare_recovery)
+		bri->unprepare_recovery(bri);
+
+	return ret;
+}
+
+int i2c_generic_scl_recovery(struct i2c_adapter *adap)
+{
+	adap->bus_recovery_info->set_scl(adap, 1);
+	return i2c_generic_recovery(adap);
+}
+
+int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
+{
+	int ret;
+
+	ret = i2c_get_gpios_for_recovery(adap);
+	if (ret)
+		return ret;
+
+	ret = i2c_generic_recovery(adap);
+	i2c_put_gpios_for_recovery(adap);
+
+	return ret;
+}
+
+int i2c_recover_bus(struct i2c_adapter *adap)
+{
+	if (!adap->bus_recovery_info)
+		return -EOPNOTSUPP;
+
+	dev_dbg(&adap->dev, "Trying i2c bus recovery\n");
+	return adap->bus_recovery_info->recover_bus(adap);
+}
+
 static int i2c_device_probe(struct device *dev)
 {
 	struct i2c_client	*client = i2c_verify_client(dev);
@@ -902,6 +1029,39 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
 			 "Failed to create compatibility class link\n");
 #endif
 
+	/* bus recovery specific initialization */
+	if (adap->bus_recovery_info) {
+		struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+
+		if (!bri->recover_bus) {
+			dev_err(&adap->dev, "No recover_bus() found, not using recovery\n");
+			adap->bus_recovery_info = NULL;
+			goto exit_recovery;
+		}
+
+		/* Generic GPIO recovery */
+		if (bri->recover_bus == i2c_generic_gpio_recovery) {
+			if (!gpio_is_valid(bri->scl_gpio)) {
+				dev_err(&adap->dev, "Invalid SCL gpio, not using recovery\n");
+				adap->bus_recovery_info = NULL;
+				goto exit_recovery;
+			}
+
+			if (gpio_is_valid(bri->sda_gpio))
+				bri->get_sda = get_sda_gpio_value;
+			else
+				bri->get_sda = NULL;
+
+			bri->get_scl = get_scl_gpio_value;
+			bri->set_scl = set_scl_gpio_value;
+		} else if (!bri->set_scl || !bri->get_scl) {
+			/* Generic SCL recovery */
+			dev_err(&adap->dev, "No get[set]_gpio() found, not using recovery\n");
+			adap->bus_recovery_info = NULL;
+		}
+	}
+
+exit_recovery:
 	/* create pre-declared device nodes */
 	if (adap->nr < __i2c_first_dynamic_bus_num)
 		i2c_scan_static_board_info(adap);
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index d0c4db7..05a1966 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -370,6 +370,44 @@ struct i2c_algorithm {
 	u32 (*functionality) (struct i2c_adapter *);
 };
 
+/**
+ * struct i2c_bus_recovery_info - I2C bus recovery information
+ * @recover_bus: Recover routine. Either pass driver's recover_bus() routine, or
+ *	i2c_generic_scl_recovery() or i2c_generic_gpio_recovery().
+ * @get_scl: This gets current value of SCL line. Mandatory for generic SCL
+ *      recovery. Used internally for generic GPIO recovery.
+ * @set_scl: This sets/clears SCL line. Mandatory for generic SCL recovery. Used
+ *      internally for generic GPIO recovery.
+ * @get_sda: This gets current value of SDA line. Optional for generic SCL
+ *      recovery. Used internally, if sda_gpio is a valid GPIO, for generic GPIO
+ *      recovery.
+ * @prepare_recovery: This will be called before starting recovery. Platform may
+ *	configure padmux here for SDA/SCL line or something else they want.
+ * @unprepare_recovery: This will be called after completing recovery. Platform
+ *	may configure padmux here for SDA/SCL line or something else they want.
+ * @scl_gpio: gpio number of the SCL line. Only required for GPIO recovery.
+ * @sda_gpio: gpio number of the SDA line. Only required for GPIO recovery.
+ */
+struct i2c_bus_recovery_info {
+	int (*recover_bus)(struct i2c_adapter *);
+
+	int (*get_scl)(struct i2c_adapter *);
+	void (*set_scl)(struct i2c_adapter *, int val);
+	int (*get_sda)(struct i2c_adapter *);
+
+	void (*prepare_recovery)(struct i2c_bus_recovery_info *bri);
+	void (*unprepare_recovery)(struct i2c_bus_recovery_info *bri);
+
+	/* gpio recovery */
+	unsigned scl_gpio;
+	unsigned sda_gpio;
+};
+
+/* Generic recovery routines */
+int i2c_generic_gpio_recovery(struct i2c_adapter *adap);
+int i2c_generic_scl_recovery(struct i2c_adapter *adap);
+int i2c_recover_bus(struct i2c_adapter *adap);
+
 /*
  * i2c_adapter is the structure used to identify a physical i2c bus along
  * with the access algorithms necessary to access it.
@@ -393,6 +431,8 @@ struct i2c_adapter {
 
 	struct mutex userspace_clients_lock;
 	struct list_head userspace_clients;
+
+	struct i2c_bus_recovery_info *bus_recovery_info;
 };
 #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
 
-- 
1.7.12.rc2.18.g61b472e


[-- Attachment #3: 0002-i2c-designware-Provide-i2c-bus-recovery-support.patch --]
[-- Type: application/octet-stream, Size: 2327 bytes --]

From 6ea3f443f668ca87dc3ec1f302551c30d532e5c1 Mon Sep 17 00:00:00 2001
Message-Id: <6ea3f443f668ca87dc3ec1f302551c30d532e5c1.1359177099.git.viresh.kumar@linaro.org>
In-Reply-To: <68f1dea5e585a7cf4d719232ff94c02aef8620e6.1359177099.git.viresh.kumar@linaro.org>
References: <68f1dea5e585a7cf4d719232ff94c02aef8620e6.1359177099.git.viresh.kumar@linaro.org>
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: Wed, 29 Feb 2012 23:16:15 +0530
Subject: [PATCH V11 2/2] i2c/designware: Provide i2c bus recovery support

Add bus recovery support for designware_i2c controller. It uses generic gpio
based i2c_gpio_recover_bus() routine. Platforms need to pass struct
i2c_bus_recovery_info as platform data to designware I2C controller.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@st.com>
Signed-off-by: Shiraz Hashim <shiraz.hashim@st.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/i2c/busses/i2c-designware-core.c    | 5 ++++-
 drivers/i2c/busses/i2c-designware-platdrv.c | 6 ++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index f5258c2..d0423ef 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -539,7 +539,10 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 	ret = wait_for_completion_interruptible_timeout(&dev->cmd_complete, HZ);
 	if (ret == 0) {
 		dev_err(dev->dev, "controller timed out\n");
-		i2c_dw_init(dev);
+
+		if (i2c_recover_bus(adap) < 0)
+			i2c_dw_init(dev);
+
 		ret = -ETIMEDOUT;
 		goto done;
 	} else if (ret < 0)
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 343357a..9142f0c 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -141,6 +141,12 @@ static int dw_i2c_probe(struct platform_device *pdev)
 	adap->dev.parent = &pdev->dev;
 	adap->dev.of_node = pdev->dev.of_node;
 
+	/* Bus recovery support */
+	adap->bus_recovery_info = dev_get_platdata(&pdev->dev);
+	if (adap->bus_recovery_info)
+		adap->bus_recovery_info->recover_bus =
+			i2c_generic_gpio_recovery;
+
 	adap->nr = pdev->id;
 	r = i2c_add_numbered_adapter(adap);
 	if (r) {
-- 
1.7.12.rc2.18.g61b472e