On Tue, Jul 07, 2015 at 12:54:51AM +0530, Vaibhav Hiremath wrote:
> From: Yi Zhang <yizhang@xxxxxxxxxxx>
>
> Enable i2c module/unit before transmission and disable when it finishes.
>
> why?
> It's because the i2c bus may be distrubed if the slave device,
> typically a touch, powers on.
>
> As we do not want to break slave mode support, this patch introduces
> DT property to control disable of the I2C module after xfer in master mode
> of operation.
>
> i2c-disable-after-xfer : If set, driver will disable I2C module after msg xfer
Hmm, I am not sure this property fits into the "describing hardware"
category. And we can't make the below behaviour default, because the
udelay(100) will cause quite some latency.
>
> Signed-off-by: Yi Zhang <yizhang@xxxxxxxxxxx>
> Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@xxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-pxa.c | 43 +++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 41 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-pxa.c b/drivers/i2c/busses/i2c-pxa.c
> index 2de9300..dfd1dd0 100644
> --- a/drivers/i2c/busses/i2c-pxa.c
> +++ b/drivers/i2c/busses/i2c-pxa.c
> @@ -161,6 +161,7 @@ struct pxa_i2c {
> unsigned char master_code;
> unsigned long rate;
> bool highmode_enter;
> + bool disable_after_xfer;
> };
>
> #define _IBMR(i2c) ((i2c)->reg_ibmr)
> @@ -284,6 +285,24 @@ static void i2c_pxa_scream_blue_murder(struct pxa_i2c *i2c, const char *why)
> static void i2c_pxa_master_complete(struct pxa_i2c *i2c, int ret);
> static irqreturn_t i2c_pxa_handler(int this_irq, void *dev_id);
>
> +/* enable/disable i2c unit */
> +static inline int i2c_pxa_is_enabled(struct pxa_i2c *i2c)
> +{
> + return (readl(_ICR(i2c)) & ICR_IUE);
> +}
> +
> +static inline void i2c_pxa_enable(struct pxa_i2c *i2c, bool enable)
> +{
> + if (enable) {
> + if (!i2c_pxa_is_enabled(i2c)) {
> + writel(readl(_ICR(i2c)) | ICR_IUE, _ICR(i2c));
> + udelay(100);
> + }
> + } else {
> + writel(readl(_ICR(i2c)) & ~ICR_IUE, _ICR(i2c));
> + }
> +}
> +
> static inline int i2c_pxa_is_slavemode(struct pxa_i2c *i2c)
> {
> return !(readl(_ICR(i2c)) & ICR_SCLE);
> @@ -480,8 +499,7 @@ static void i2c_pxa_reset(struct pxa_i2c *i2c)
> i2c_pxa_set_slave(i2c, 0);
>
> /* enable unit */
> - writel(readl(_ICR(i2c)) | ICR_IUE, _ICR(i2c));
> - udelay(100);
> + i2c_pxa_enable(i2c, true);
> }
>
>
> @@ -832,6 +850,9 @@ static int i2c_pxa_pio_xfer(struct i2c_adapter *adap,
> struct pxa_i2c *i2c = adap->algo_data;
> int ret, i;
>
> + /* Enable i2c unit */
> + i2c_pxa_enable(i2c, true);
> +
> /* If the I2C controller is disabled we need to reset it
> (probably due to a suspend/resume destroying state). We do
> this here as we can then avoid worrying about resuming the
> @@ -852,6 +873,11 @@ static int i2c_pxa_pio_xfer(struct i2c_adapter *adap,
> ret = -EREMOTEIO;
> out:
> i2c_pxa_set_slave(i2c, ret);
> +
> + /* disable i2c unit */
> + if (i2c->disable_after_xfer)
> + i2c_pxa_enable(i2c, false);
> +
> return ret;
> }
>
> @@ -1067,6 +1093,9 @@ static int i2c_pxa_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num
> struct pxa_i2c *i2c = adap->algo_data;
> int ret, i;
>
> + /* Enable i2c unit */
> + i2c_pxa_enable(i2c, true);
> +
> for (i = adap->retries; i >= 0; i--) {
> ret = i2c_pxa_do_xfer(i2c, msgs, num);
> if (ret != I2C_RETRY)
> @@ -1080,6 +1109,10 @@ static int i2c_pxa_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num
> ret = -EREMOTEIO;
> out:
> i2c_pxa_set_slave(i2c, ret);
> + /* disable i2c unit */
> + if (i2c->disable_after_xfer)
> + i2c_pxa_enable(i2c, false);
> +
> return ret;
> }
>
> @@ -1120,6 +1153,9 @@ static int i2c_pxa_probe_dt(struct platform_device *pdev, struct pxa_i2c *i2c,
> /* For device tree we always use the dynamic or alias-assigned ID */
> i2c->adap.nr = -1;
>
> + i2c->disable_after_xfer = of_property_read_bool(np,
> + "i2c-disable-after-xfer");
> +
> if (of_get_property(np, "mrvl,i2c-polling", NULL))
> i2c->use_pio = 1;
> if (of_get_property(np, "mrvl,i2c-fast-mode", NULL))
> @@ -1271,6 +1307,9 @@ static int i2c_pxa_probe(struct platform_device *dev)
>
> platform_set_drvdata(dev, i2c);
>
> + if (i2c->disable_after_xfer)
> + i2c_pxa_enable(i2c, false);
> +
> #ifdef CONFIG_I2C_PXA_SLAVE
> dev_info(&i2c->adap.dev, " PXA I2C adapter, slave address %d\n",
> i2c->slave_addr);
> --
> 1.9.1
>
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