| Message ID | 1540378203-1655-1-git-send-email-shubhrajyoti.datta@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | i2c: cadence: Implement timeout | expand |
On Wed, Oct 24, 2018 at 04:20:03PM +0530, shubhrajyoti.datta@gmail.com wrote: > From: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com> > > In some cases we are waiting in a loop. Replace the infinite wait with > the timeout. > > Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com> > --- > 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(&id->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.
On Wed, Oct 24, 2018 at 4:29 PM Russell King - ARM Linux <linux@armlinux.org.uk> wrote: > > On Wed, Oct 24, 2018 at 04:20:03PM +0530, shubhrajyoti.datta@gmail.com wrote: > > From: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com> > > > > In some cases we are waiting in a loop. Replace the infinite wait with > > the timeout. > > > > Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com> > > --- > > 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(&id->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. Thanks for the review. I agree will skip this patch.
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(&id->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(&id->xfer_done); + return IRQ_HANDLED; + } /* * Check number of bytes to be received against maximum * transfer size and update register accordingly.