Re: [PATCH-v5 2/5] i2c: pxa: enable/disable i2c module across msg xfer
On Wednesday 05 August 2015 04:16 PM, Shubhrajyoti Datta wrote: hi , On Tue, Jul 21, 2015 at 6:11 PM, Vaibhav Hiremath wrote: From: Yi Zhang Enable i2c module/unit before transmission and disable when it finishes. why? It's because the i2c bus may be disturbed if the slave device, typically a touch, powers on. Why should that be an issue? Is it an errata. Not I am aware of. In which mode it is an issue slave / master or both? since it talks about touch, I expect it to be master mode. Thanks, Vaibhav -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH-v5 2/5] i2c: pxa: enable/disable i2c module across msg xfer
hi , On Tue, Jul 21, 2015 at 6:11 PM, Vaibhav Hiremath wrote: > From: Yi Zhang > > Enable i2c module/unit before transmission and disable when it > finishes. > > why? > It's because the i2c bus may be disturbed if the slave device, > typically a touch, powers on. Why should that be an issue? Is it an errata. In which mode it is an issue slave / master or both? > > 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 > > Signed-off-by: Yi Zhang > Signed-off-by: Vaibhav Hiremath > --- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH-v5 2/5] i2c: pxa: enable/disable i2c module across msg xfer
hi , On Tue, Jul 21, 2015 at 6:11 PM, Vaibhav Hiremath vaibhav.hirem...@linaro.org wrote: From: Yi Zhang yizh...@marvell.com Enable i2c module/unit before transmission and disable when it finishes. why? It's because the i2c bus may be disturbed if the slave device, typically a touch, powers on. Why should that be an issue? Is it an errata. In which mode it is an issue slave / master or both? 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 Signed-off-by: Yi Zhang yizh...@marvell.com Signed-off-by: Vaibhav Hiremath vaibhav.hirem...@linaro.org --- -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH-v5 2/5] i2c: pxa: enable/disable i2c module across msg xfer
On Wednesday 05 August 2015 04:16 PM, Shubhrajyoti Datta wrote: hi , On Tue, Jul 21, 2015 at 6:11 PM, Vaibhav Hiremath vaibhav.hirem...@linaro.org wrote: From: Yi Zhang yizh...@marvell.com Enable i2c module/unit before transmission and disable when it finishes. why? It's because the i2c bus may be disturbed if the slave device, typically a touch, powers on. Why should that be an issue? Is it an errata. Not I am aware of. In which mode it is an issue slave / master or both? since it talks about touch, I expect it to be master mode. Thanks, Vaibhav -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH-v5 2/5] i2c: pxa: enable/disable i2c module across msg xfer
From: Yi Zhang
Enable i2c module/unit before transmission and disable when it
finishes.
why?
It's because the i2c bus may be disturbed 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
Signed-off-by: Yi Zhang
Signed-off-by: Vaibhav Hiremath
---
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 66cf437..abf04f2 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;
boolhighmode_enter;
+ booldisable_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))
@@ -1264,6 +1300,9 @@ 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(>adap.dev, " PXA I2C adapter, slave address %d\n",
i2c->slave_addr);
--
1.9.1
--
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Please read the FAQ at http://www.tux.org/lkml/
[PATCH-v5 2/5] i2c: pxa: enable/disable i2c module across msg xfer
From: Yi Zhang yizh...@marvell.com
Enable i2c module/unit before transmission and disable when it
finishes.
why?
It's because the i2c bus may be disturbed 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
Signed-off-by: Yi Zhang yizh...@marvell.com
Signed-off-by: Vaibhav Hiremath vaibhav.hirem...@linaro.org
---
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 66cf437..abf04f2 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;
boolhighmode_enter;
+ booldisable_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))
@@ -1264,6 +1300,9 @@ 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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the body of a message to majord...@vger.kernel.org
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