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Date: Fri, 21 Nov 2014 20:07:44 +0100
From: Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>
To: Grygorii Strashko <grygorii.strashko@...com>
Cc: Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
linux-kernel@...r.kernel.org, Sekhar Nori <nsekhar@...com>,
Kevin Hilman <khilman@...prootsystems.com>,
Santosh Shilimkar <ssantosh@...nel.org>,
Murali Karicheri <m-karicheri2@...com>
Subject: Re: [4/5] i2c: davinci: use bus recovery infrastructure
On Thu, Nov 20, 2014 at 12:03:07PM +0200, Grygorii Strashko wrote:
> This patch converts Davinci I2C driver to use I2C bus recovery
> infrastructure, introduced by commit 5f9296ba21b3 ("i2c: Add
> bus recovery infrastructure").
>
> The i2c_bus_recovery_info is configured for Davinci I2C adapter
> only in case if scl_pin is provided in Platform data at least.
s/Platform/platform/
>
> Because the controller must be held in reset while doing so, the
s/Because/As/
> recovery routine must re-init the controller. Since this was already
> being done after each call to i2c_recover_bus, move those calls into
> the recovery_prepare/unprepare routines and as well.
>
> CC: Sekhar Nori <nsekhar@...com>
> CC: Kevin Hilman <khilman@...prootsystems.com>
> CC: Santosh Shilimkar <ssantosh@...nel.org>
> CC: Murali Karicheri <m-karicheri2@...com>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> ---
> drivers/i2c/busses/i2c-davinci.c | 76 ++++++++++++++++++----------------------
> 1 file changed, 35 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
> index 2cef115..db2a2cd 100644
> --- a/drivers/i2c/busses/i2c-davinci.c
> +++ b/drivers/i2c/busses/i2c-davinci.c
> @@ -133,43 +133,6 @@ 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 +229,33 @@ 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"
> + */
This comment is wrong. The actual bus clear is implemented by
i2c_generic_gpio_recovery. Also while touching this comment, convert it
to the usual format with /* on its own line. (The file in question has
already both types of comment, so consistency is not a reason to keep it
as is.)
Even though I remember that I reviewed this bus recovery patch (that
resulted in 5f9296ba21b3) back then, I don't remember why it was split
in prepare + recover + unprepare. But that is unrelated to this patch.
> +static void davinci_i2c_prepare_recovery(struct i2c_adapter *adap)
> +{
> + struct davinci_i2c_dev *dev = i2c_get_adapdata(adap);
> +
> + 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);
> +}
> +
> +static void davinci_i2c_unprepare_recovery(struct i2c_adapter *adap)
> +{
> + struct davinci_i2c_dev *dev = i2c_get_adapdata(adap);
> +
> + i2c_davinci_init(dev);
> +}
> +
> +static struct i2c_bus_recovery_info davinci_i2c_gpio_recovery_info = {
I'd call this only davinci_i2c_recovery_info.
> + .recover_bus = i2c_generic_gpio_recovery,
> + .prepare_recovery = davinci_i2c_prepare_recovery,
> + .unprepare_recovery = davinci_i2c_unprepare_recovery,
> +};
new line here please
> /*
> * Waiting for bus not busy
> */
> @@ -286,8 +276,7 @@ static int i2c_davinci_wait_bus_not_busy(struct davinci_i2c_dev *dev,
> return -ETIMEDOUT;
> } else {
> to_cnt = 0;
> - davinci_i2c_recover_bus(dev);
> - i2c_davinci_init(dev);
> + i2c_recover_bus(&dev->adapter);
> }
> }
> if (allow_sleep)
> @@ -376,8 +365,7 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
> dev->adapter.timeout);
> if (r == 0) {
> dev_err(dev->dev, "controller timed out\n");
> - davinci_i2c_recover_bus(dev);
> - i2c_davinci_init(dev);
> + i2c_recover_bus(adap);
> dev->buf_len = 0;
> return -ETIMEDOUT;
> }
> @@ -717,6 +705,12 @@ static int davinci_i2c_probe(struct platform_device *pdev)
> adap->timeout = DAVINCI_I2C_TIMEOUT;
> adap->dev.of_node = pdev->dev.of_node;
>
> + if (dev->pdata->scl_pin) {
> + adap->bus_recovery_info = &davinci_i2c_gpio_recovery_info;
> + adap->bus_recovery_info->scl_gpio = dev->pdata->scl_pin;
> + adap->bus_recovery_info->sda_gpio = dev->pdata->sda_pin;
> + }
> +
> adap->nr = pdev->id;
> r = i2c_add_numbered_adapter(adap);
> if (r) {
Just another general comment about the driver that doesn't influence the
correctness of this patch: The i2c-davinci driver is quite quick to
reset the bus. I wonder how often this reset triggers. Is the bus in
question less "stable" than others?
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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