Re: [PATCH] i2c: cadence: Implement timeout
On Wed, Oct 24, 2018 at 04:20:03PM +0530, shubhrajyoti.da...@gmail.com wrote:
> From: Shubhrajyoti Datta
>
> In some cases we are waiting in a loop. Replace the infinite wait with
> the timeout.
>
> Signed-off-by: Shubhrajyoti Datta
> ---
> drivers/i2c/busses/i2c-cadence.c | 30 ++
> 1 file changed, 26 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-cadence.c
> b/drivers/i2c/busses/i2c-cadence.c
> index b136057..9c38278 100644
> --- a/drivers/i2c/busses/i2c-cadence.c
> +++ b/drivers/i2c/busses/i2c-cadence.c
> @@ -209,6 +209,7 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
> struct cdns_i2c *id = ptr;
> /* Signal completion only after everything is updated */
> int done_flag = 0;
> + unsigned int timeout;
> irqreturn_t status = IRQ_NONE;
>
> isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
> @@ -235,6 +236,7 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
> ((isr_status & CDNS_I2C_IXR_COMP) ||
>(isr_status & CDNS_I2C_IXR_DATA))) {
> /* Read data if receive data valid is set */
> + timeout = 1000;
> while (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) &
> CDNS_I2C_SR_RXDV) {
> /*
> @@ -253,6 +255,16 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
>
> if (cdns_is_holdquirk(id, hold_quirk))
> break;
> + timeout--;
> + if (timeout)
> + mdelay(1);
> + else
> + break;
> + }
> + if (!timeout) {
> + id->err_status = -ETIMEDOUT;
> + complete(>xfer_done);
> + return IRQ_HANDLED;
Good kernel programming principle: Always check for the success
condition when exiting due to timeout rather than the fact that we
timed out.
Also, is this _really_ a loop that needs a timeout condition? Looking
at the original code, it looks like the purpose of the loop is to read
more than one byte, and you are introducing a 1ms delay between the
read of each byte.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
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Re: [PATCH] i2c: cadence: Implement timeout
On Wed, Oct 24, 2018 at 04:20:03PM +0530, shubhrajyoti.da...@gmail.com wrote:
> From: Shubhrajyoti Datta
>
> In some cases we are waiting in a loop. Replace the infinite wait with
> the timeout.
>
> Signed-off-by: Shubhrajyoti Datta
> ---
> drivers/i2c/busses/i2c-cadence.c | 30 ++
> 1 file changed, 26 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-cadence.c
> b/drivers/i2c/busses/i2c-cadence.c
> index b136057..9c38278 100644
> --- a/drivers/i2c/busses/i2c-cadence.c
> +++ b/drivers/i2c/busses/i2c-cadence.c
> @@ -209,6 +209,7 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
> struct cdns_i2c *id = ptr;
> /* Signal completion only after everything is updated */
> int done_flag = 0;
> + unsigned int timeout;
> irqreturn_t status = IRQ_NONE;
>
> isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
> @@ -235,6 +236,7 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
> ((isr_status & CDNS_I2C_IXR_COMP) ||
>(isr_status & CDNS_I2C_IXR_DATA))) {
> /* Read data if receive data valid is set */
> + timeout = 1000;
> while (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) &
> CDNS_I2C_SR_RXDV) {
> /*
> @@ -253,6 +255,16 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
>
> if (cdns_is_holdquirk(id, hold_quirk))
> break;
> + timeout--;
> + if (timeout)
> + mdelay(1);
> + else
> + break;
> + }
> + if (!timeout) {
> + id->err_status = -ETIMEDOUT;
> + complete(>xfer_done);
> + return IRQ_HANDLED;
Good kernel programming principle: Always check for the success
condition when exiting due to timeout rather than the fact that we
timed out.
Also, is this _really_ a loop that needs a timeout condition? Looking
at the original code, it looks like the purpose of the loop is to read
more than one byte, and you are introducing a 1ms delay between the
read of each byte.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up
[PATCH] i2c: cadence: Implement timeout
From: Shubhrajyoti Datta
In some cases we are waiting in a loop. Replace the infinite wait with
the timeout.
Signed-off-by: Shubhrajyoti Datta
---
drivers/i2c/busses/i2c-cadence.c | 30 ++
1 file changed, 26 insertions(+), 4 deletions(-)
diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index b136057..9c38278 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -209,6 +209,7 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
struct cdns_i2c *id = ptr;
/* Signal completion only after everything is updated */
int done_flag = 0;
+ unsigned int timeout;
irqreturn_t status = IRQ_NONE;
isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
@@ -235,6 +236,7 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
((isr_status & CDNS_I2C_IXR_COMP) ||
(isr_status & CDNS_I2C_IXR_DATA))) {
/* Read data if receive data valid is set */
+ timeout = 1000;
while (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) &
CDNS_I2C_SR_RXDV) {
/*
@@ -253,6 +255,16 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
if (cdns_is_holdquirk(id, hold_quirk))
break;
+ timeout--;
+ if (timeout)
+ mdelay(1);
+ else
+ break;
+ }
+ if (!timeout) {
+ id->err_status = -ETIMEDOUT;
+ complete(>xfer_done);
+ return IRQ_HANDLED;
}
/*
@@ -262,12 +274,22 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
* maintain transfer size non-zero while performing a large
* receive operation.
*/
+ timeout = 1000;
if (cdns_is_holdquirk(id, hold_quirk)) {
/* wait while fifo is full */
- while (cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET) !=
- (id->curr_recv_count - CDNS_I2C_FIFO_DEPTH))
- ;
-
+ while ((cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET) !=
+ (id->curr_recv_count - CDNS_I2C_FIFO_DEPTH))) {
+ timeout--;
+ if (timeout)
+ mdelay(1);
+ else
+ break;
+ }
+ if (!timeout) {
+ id->err_status = -ETIMEDOUT;
+ complete(>xfer_done);
+ return IRQ_HANDLED;
+ }
/*
* Check number of bytes to be received against maximum
* transfer size and update register accordingly.
--
2.1.1
[PATCH] i2c: cadence: Implement timeout
From: Shubhrajyoti Datta
In some cases we are waiting in a loop. Replace the infinite wait with
the timeout.
Signed-off-by: Shubhrajyoti Datta
---
drivers/i2c/busses/i2c-cadence.c | 30 ++
1 file changed, 26 insertions(+), 4 deletions(-)
diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index b136057..9c38278 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -209,6 +209,7 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
struct cdns_i2c *id = ptr;
/* Signal completion only after everything is updated */
int done_flag = 0;
+ unsigned int timeout;
irqreturn_t status = IRQ_NONE;
isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
@@ -235,6 +236,7 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
((isr_status & CDNS_I2C_IXR_COMP) ||
(isr_status & CDNS_I2C_IXR_DATA))) {
/* Read data if receive data valid is set */
+ timeout = 1000;
while (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) &
CDNS_I2C_SR_RXDV) {
/*
@@ -253,6 +255,16 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
if (cdns_is_holdquirk(id, hold_quirk))
break;
+ timeout--;
+ if (timeout)
+ mdelay(1);
+ else
+ break;
+ }
+ if (!timeout) {
+ id->err_status = -ETIMEDOUT;
+ complete(>xfer_done);
+ return IRQ_HANDLED;
}
/*
@@ -262,12 +274,22 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
* maintain transfer size non-zero while performing a large
* receive operation.
*/
+ timeout = 1000;
if (cdns_is_holdquirk(id, hold_quirk)) {
/* wait while fifo is full */
- while (cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET) !=
- (id->curr_recv_count - CDNS_I2C_FIFO_DEPTH))
- ;
-
+ while ((cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET) !=
+ (id->curr_recv_count - CDNS_I2C_FIFO_DEPTH))) {
+ timeout--;
+ if (timeout)
+ mdelay(1);
+ else
+ break;
+ }
+ if (!timeout) {
+ id->err_status = -ETIMEDOUT;
+ complete(>xfer_done);
+ return IRQ_HANDLED;
+ }
/*
* Check number of bytes to be received against maximum
* transfer size and update register accordingly.
--
2.1.1
