[PATCH] i2c-davinci: Implement a bus recovery that actually works

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[PATCH] i2c-davinci: Implement a bus recovery that actually works

Mike Looijmans
From: Mike Looijmans <[hidden email]>

Having a board where the I2C bus locks up occasionally made it clear
that the bus recovery in the i2c-davinci driver will only work on
some boards, because on regular boards, this will only toggle GPIO
lines that aren't muxed to the actual pins.

The I2C controller has the built-in capability to bit-bang its lines.
Use this to implement a generic recovery routine that puts the
controller in GPIO mode and pulse the clk lines until both SDA and
SCL return to a high state.

Because the controller must be held in reset while doing so, the
recovery routine must re-init the controller. Since this was already
being done after each call to i2c_recover_bus, move that call into
the recovery routine as well.

Tested on a custom board with OMAP-L138, and after this change, the
board can recover from chips keeping SDA low.

Note: This is an adapted port from 2.6.37 code, and was only tested
with that kernel.
---
 drivers/i2c/busses/i2c-davinci.c |   83 ++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 39 deletions(-)

diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
index af0b583..1ee04c4 100644
--- a/drivers/i2c/busses/i2c-davinci.c
+++ b/drivers/i2c/busses/i2c-davinci.c
@@ -64,6 +64,10 @@
 #define DAVINCI_I2C_IVR_REG 0x28
 #define DAVINCI_I2C_EMDR_REG 0x2c
 #define DAVINCI_I2C_PSC_REG 0x30
+#define DAVINCI_I2C_FUNC_REG 0x48
+#define DAVINCI_I2C_DIR_REG 0x4c
+#define DAVINCI_I2C_DIN_REG 0x50
+#define DAVINCI_I2C_DOUT_REG 0x54
 
 #define DAVINCI_I2C_IVR_AAS 0x07
 #define DAVINCI_I2C_IVR_SCD 0x06
@@ -133,43 +137,6 @@ static inline u16 davinci_i2c_read_reg(struct davinci_i2c_dev *i2c_dev, int reg)
  return readw_relaxed(i2c_dev->base + reg);
 }
 
-/* Generate a pulse on the i2c clock pin. */
-static void davinci_i2c_clock_pulse(unsigned int scl_pin)
-{
- u16 i;
-
- if (scl_pin) {
- /* Send high and low on the SCL line */
- for (i = 0; i < 9; i++) {
- gpio_set_value(scl_pin, 0);
- udelay(20);
- gpio_set_value(scl_pin, 1);
- udelay(20);
- }
- }
-}
-
-/* This routine does i2c bus recovery as specified in the
- * i2c protocol Rev. 03 section 3.16 titled "Bus clear"
- */
-static void davinci_i2c_recover_bus(struct davinci_i2c_dev *dev)
-{
- u32 flag = 0;
- struct davinci_i2c_platform_data *pdata = dev->pdata;
-
- dev_err(dev->dev, "initiating i2c bus recovery\n");
- /* Send NACK to the slave */
- flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
- flag |=  DAVINCI_I2C_MDR_NACK;
- /* write the data into mode register */
- davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
- davinci_i2c_clock_pulse(pdata->scl_pin);
- /* Send STOP */
- flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
- flag |= DAVINCI_I2C_MDR_STP;
- davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
-}
-
 static inline void davinci_i2c_reset_ctrl(struct davinci_i2c_dev *i2c_dev,
  int val)
 {
@@ -266,6 +233,46 @@ static int i2c_davinci_init(struct davinci_i2c_dev *dev)
  return 0;
 }
 
+/* This routine does i2c bus recovery as specified in the
+ * i2c protocol Rev. 03 section 3.16 titled "Bus clear"
+ */
+static void i2c_recover_bus(struct davinci_i2c_dev *dev)
+{
+ u32 flag = 0;
+ int i;
+ struct davinci_i2c_platform_data *pdata = dev->dev->platform_data;
+ flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_DIN_REG);
+ if ((flag & 0x01) == 0)
+ dev_err(dev->dev, "SCL stuck at zero.\n");
+ dev_err(dev->dev, "initiating i2c bus recovery\n");
+ /* Disable interrupts */
+ davinci_i2c_write_reg(dev, DAVINCI_I2C_IMR_REG, 0);
+ /* put I2C into reset */
+ davinci_i2c_reset_ctrl(dev, 0);
+ /* Set GPIO mode */
+ davinci_i2c_write_reg(dev, DAVINCI_I2C_FUNC_REG, 0x1);
+ /* Set scl=1 sda=1 */
+ davinci_i2c_write_reg(dev, DAVINCI_I2C_DOUT_REG, 0x03);
+ /* Set SCL pin as output, SDA as input */
+ davinci_i2c_write_reg(dev, DAVINCI_I2C_DIR_REG, 0x1);
+ /* Send up to 9 clock pulses until SDA is high */
+ for (i = 0; i < 9; ++i) {
+ davinci_i2c_write_reg(dev, DAVINCI_I2C_DOUT_REG, 0x02); /* scl=0 sda=1 */
+ udelay(10);
+ davinci_i2c_write_reg(dev, DAVINCI_I2C_DOUT_REG, 0x03);
+ udelay(10);
+ /* Register DIN reads actual state on line */
+ flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_DIN_REG);
+ if ((flag & 0x3) == 0x3) {
+ dev_info(dev->dev, "SDA and SCL high again (i=%d), resume.\n", i);
+ break;
+ }
+ }
+ /* Resume operation */
+ davinci_i2c_write_reg(dev, DAVINCI_I2C_FUNC_REG, 0x0);
+ i2c_davinci_init(dev);
+}
+
 /*
  * Waiting for bus not busy
  */
@@ -287,7 +294,6 @@ static int i2c_davinci_wait_bus_not_busy(struct davinci_i2c_dev *dev,
  } else {
  to_cnt = 0;
  davinci_i2c_recover_bus(dev);
- i2c_davinci_init(dev);
  }
  }
  if (allow_sleep)
@@ -377,7 +383,6 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
  if (r == 0) {
  dev_err(dev->dev, "controller timed out\n");
  davinci_i2c_recover_bus(dev);
- i2c_davinci_init(dev);
  dev->buf_len = 0;
  return -ETIMEDOUT;
  }
--
1.7.9.5

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Re: [PATCH] i2c-davinci: Implement a bus recovery that actually works

Wolfram Sang-2
On Fri, Feb 28, 2014 at 11:32:05AM +0100, [hidden email] wrote:

> From: Mike Looijmans <[hidden email]>
>
> Having a board where the I2C bus locks up occasionally made it clear
> that the bus recovery in the i2c-davinci driver will only work on
> some boards, because on regular boards, this will only toggle GPIO
> lines that aren't muxed to the actual pins.
>
> The I2C controller has the built-in capability to bit-bang its lines.
> Use this to implement a generic recovery routine that puts the
> controller in GPIO mode and pulse the clk lines until both SDA and
> SCL return to a high state.
>
> Because the controller must be held in reset while doing so, the
> recovery routine must re-init the controller. Since this was already
> being done after each call to i2c_recover_bus, move that call into
> the recovery routine as well.
>
> Tested on a custom board with OMAP-L138, and after this change, the
> board can recover from chips keeping SDA low.
>
> Note: This is an adapted port from 2.6.37 code, and was only tested
> with that kernel.
What about using struct i2c_bus_recovery_info, so the actual recovery
logic is taken from the core?

Thanks,

   Wolfram


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Re: [PATCH] i2c-davinci: Implement a bus recovery that actually works

Mike Looijmans
On 03/09/2014 09:28 PM, Wolfram Sang wrote:

> On Fri, Feb 28, 2014 at 11:32:05AM +0100, [hidden email] wrote:
>> From: Mike Looijmans <[hidden email]>
>>
>> Having a board where the I2C bus locks up occasionally made it clear
>> that the bus recovery in the i2c-davinci driver will only work on
>> some boards, because on regular boards, this will only toggle GPIO
>> lines that aren't muxed to the actual pins.
>>
>> The I2C controller has the built-in capability to bit-bang its lines.
>> Use this to implement a generic recovery routine that puts the
>> controller in GPIO mode and pulse the clk lines until both SDA and
>> SCL return to a high state.
>>
>> Because the controller must be held in reset while doing so, the
>> recovery routine must re-init the controller. Since this was already
>> being done after each call to i2c_recover_bus, move that call into
>> the recovery routine as well.
>>
>> Tested on a custom board with OMAP-L138, and after this change, the
>> board can recover from chips keeping SDA low.
>>
>> Note: This is an adapted port from 2.6.37 code, and was only tested
>> with that kernel.
>
> What about using struct i2c_bus_recovery_info, so the actual recovery
> logic is taken from the core?

I never knew such a thing existed, but it sounds like a sensible thing to do.

In addition, one could also remove the "sda_pin" and "scl_pin" members from
the platform data struct, as they no longer serve any purpose after this patch.

I won't be doing those changes though. My sponsor's budget is limited, so I'm
just having to do the minimum I can get away with. Maybe someone from TI can
take it further?

Mike.


Met vriendelijke groet / kind regards,

Mike Looijmans

TOPIC Embedded Systems
Eindhovenseweg 32-C, NL-5683 KH Best
Postbus 440, NL-5680 AK Best
Telefoon: (+31) (0) 499 33 69 79
Telefax:  (+31) (0) 499 33 69 70
E-mail: [hidden email]
Website: www.topic.nl

Please consider the environment before printing this e-mail

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Re: [PATCH] i2c-davinci: Implement a bus recovery that actually works

Wolfram Sang-2

> I won't be doing those changes though. My sponsor's budget is
> limited, so I'm just having to do the minimum I can get away with.

Pity. Are you available for testing in case someone comes up with a
patch?


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Re: [PATCH] i2c-davinci: Implement a bus recovery that actually works

Mike Looijmans
On 03/10/2014 08:26 AM, Wolfram Sang wrote:
>
>> I won't be doing those changes though. My sponsor's budget is
>> limited, so I'm just having to do the minimum I can get away with.
>
> Pity. Are you available for testing in case someone comes up with a
> patch?
>

Not really, the customer is using a 2.6.37 kernel, and that's currently the
only board we have with an OMAP-L1.

Mike.


Met vriendelijke groet / kind regards,

Mike Looijmans

TOPIC Embedded Systems
Eindhovenseweg 32-C, NL-5683 KH Best
Postbus 440, NL-5680 AK Best
Telefoon: (+31) (0) 499 33 69 79
Telefax:  (+31) (0) 499 33 69 70
E-mail: [hidden email]
Website: www.topic.nl

Please consider the environment before printing this e-mail

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