diff mbox

[1/4] spi: s3c64xx: modified error interrupt handling and init

Message ID 1360105784-12282-2-git-send-email-ks.giri@samsung.com
State Superseded, archived
Headers show

Commit Message

girishks2000@gmail.com Feb. 5, 2013, 11:09 p.m. UTC
The status of the interrupt is available in the status register,
so reading the clear pending register and writing back the same
value will not actually clear the pending interrupts. This patch
modifies the interrupt handler to read the status register and
clear the corresponding pending bit in the clear pending register.

Modified the hwInit function to clear all the pending interrupts.

Signed-off-by: Girish K S <ks.giri@samsung.com>
---
 drivers/spi/spi-s3c64xx.c |   41 +++++++++++++++++++++++++----------------
 1 file changed, 25 insertions(+), 16 deletions(-)

Comments

Grant Likely Feb. 6, 2013, 10:26 a.m. UTC | #1
On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S <girishks2000@gmail.com> wrote:
> The status of the interrupt is available in the status register,
> so reading the clear pending register and writing back the same
> value will not actually clear the pending interrupts. This patch
> modifies the interrupt handler to read the status register and
> clear the corresponding pending bit in the clear pending register.
> 
> Modified the hwInit function to clear all the pending interrupts.
> 
> Signed-off-by: Girish K S <ks.giri@samsung.com>
> ---
>  drivers/spi/spi-s3c64xx.c |   41 +++++++++++++++++++++++++----------------
>  1 file changed, 25 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
> index ad93231..b770f88 100644
> --- a/drivers/spi/spi-s3c64xx.c
> +++ b/drivers/spi/spi-s3c64xx.c
> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq, void *data)
>  {
>  	struct s3c64xx_spi_driver_data *sdd = data;
>  	struct spi_master *spi = sdd->master;
> -	unsigned int val;
> +	unsigned int val, clr = 0;
>  
> -	val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
> +	val = readl(sdd->regs + S3C64XX_SPI_STATUS);
>  
> -	val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
> -		S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
> -		S3C64XX_SPI_PND_TX_OVERRUN_CLR |
> -		S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
> -
> -	writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
> -
> -	if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
> +	if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
> +		clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
>  		dev_err(&spi->dev, "RX overrun\n");
> -	if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
> +	}
> +	if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
> +		clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
>  		dev_err(&spi->dev, "RX underrun\n");
> -	if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
> +	}
> +	if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
> +		clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
>  		dev_err(&spi->dev, "TX overrun\n");
> -	if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
> +	}
> +	if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
> +		clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>  		dev_err(&spi->dev, "TX underrun\n");
> +	}
> +
> +	/* Clear the pending irq by setting and then clearing it */
> +	writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
> +	writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);

Wait, what?  clr & ~clr == 0   Always.  What are you actually trying to do here?

>  
>  	return IRQ_HANDLED;
>  }
> @@ -1039,9 +1044,13 @@ static void s3c64xx_spi_hwinit(struct s3c64xx_spi_driver_data *sdd, int channel)
>  	writel(0, regs + S3C64XX_SPI_MODE_CFG);
>  	writel(0, regs + S3C64XX_SPI_PACKET_CNT);
>  
> -	/* Clear any irq pending bits */
> -	writel(readl(regs + S3C64XX_SPI_PENDING_CLR),
> -				regs + S3C64XX_SPI_PENDING_CLR);
> +	/* Clear any irq pending bits, should set and clear the bits */
> +	val = S3C64XX_SPI_PND_RX_OVERRUN_CLR |
> +		S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
> +		S3C64XX_SPI_PND_TX_OVERRUN_CLR |
> +		S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
> +	writel(val, regs + S3C64XX_SPI_PENDING_CLR);
> +	writel(val & ~val, regs + S3C64XX_SPI_PENDING_CLR);

Ditto.

g.

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girishks2000@gmail.com Feb. 6, 2013, 8:12 p.m. UTC | #2
On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely <grant.likely@secretlab.ca> wrote:
> On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S <girishks2000@gmail.com> wrote:
>> The status of the interrupt is available in the status register,
>> so reading the clear pending register and writing back the same
>> value will not actually clear the pending interrupts. This patch
>> modifies the interrupt handler to read the status register and
>> clear the corresponding pending bit in the clear pending register.
>>
>> Modified the hwInit function to clear all the pending interrupts.
>>
>> Signed-off-by: Girish K S <ks.giri@samsung.com>
>> ---
>>  drivers/spi/spi-s3c64xx.c |   41 +++++++++++++++++++++++++----------------
>>  1 file changed, 25 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>> index ad93231..b770f88 100644
>> --- a/drivers/spi/spi-s3c64xx.c
>> +++ b/drivers/spi/spi-s3c64xx.c
>> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq, void *data)
>>  {
>>       struct s3c64xx_spi_driver_data *sdd = data;
>>       struct spi_master *spi = sdd->master;
>> -     unsigned int val;
>> +     unsigned int val, clr = 0;
>>
>> -     val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> +     val = readl(sdd->regs + S3C64XX_SPI_STATUS);
>>
>> -     val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
>> -             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
>> -             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
>> -             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>> -
>> -     writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> -
>> -     if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
>> +     if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
>> +             clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
>>               dev_err(&spi->dev, "RX overrun\n");
>> -     if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
>> +     }
>> +     if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
>> +             clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
>>               dev_err(&spi->dev, "RX underrun\n");
>> -     if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
>> +     }
>> +     if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
>> +             clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
>>               dev_err(&spi->dev, "TX overrun\n");
>> -     if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
>> +     }
>> +     if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
>> +             clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>               dev_err(&spi->dev, "TX underrun\n");
>> +     }
>> +
>> +     /* Clear the pending irq by setting and then clearing it */
>> +     writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> +     writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>
> Wait, what?  clr & ~clr == 0   Always.  What are you actually trying to do here?
The user manual says, wirting 1 to the pending clear register clears
the interrupt (its not auto clear to 0). so i need to explicitly reset
those bits thats what the 2nd write does
>
>>
>>       return IRQ_HANDLED;
>>  }
>> @@ -1039,9 +1044,13 @@ static void s3c64xx_spi_hwinit(struct s3c64xx_spi_driver_data *sdd, int channel)
>>       writel(0, regs + S3C64XX_SPI_MODE_CFG);
>>       writel(0, regs + S3C64XX_SPI_PACKET_CNT);
>>
>> -     /* Clear any irq pending bits */
>> -     writel(readl(regs + S3C64XX_SPI_PENDING_CLR),
>> -                             regs + S3C64XX_SPI_PENDING_CLR);
>> +     /* Clear any irq pending bits, should set and clear the bits */
>> +     val = S3C64XX_SPI_PND_RX_OVERRUN_CLR |
>> +             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
>> +             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
>> +             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>> +     writel(val, regs + S3C64XX_SPI_PENDING_CLR);
>> +     writel(val & ~val, regs + S3C64XX_SPI_PENDING_CLR);
>
> Ditto.
same as above
>
> g.

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Grant Likely Feb. 6, 2013, 11:48 p.m. UTC | #3
On Wed, Feb 6, 2013 at 8:12 PM, Girish KS <girishks2000@gmail.com> wrote:
> On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely <grant.likely@secretlab.ca> wrote:
>> On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S <girishks2000@gmail.com> wrote:
>>> The status of the interrupt is available in the status register,
>>> so reading the clear pending register and writing back the same
>>> value will not actually clear the pending interrupts. This patch
>>> modifies the interrupt handler to read the status register and
>>> clear the corresponding pending bit in the clear pending register.
>>>
>>> Modified the hwInit function to clear all the pending interrupts.
>>>
>>> Signed-off-by: Girish K S <ks.giri@samsung.com>
>>> ---
>>>  drivers/spi/spi-s3c64xx.c |   41 +++++++++++++++++++++++++----------------
>>>  1 file changed, 25 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>>> index ad93231..b770f88 100644
>>> --- a/drivers/spi/spi-s3c64xx.c
>>> +++ b/drivers/spi/spi-s3c64xx.c
>>> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq, void *data)
>>>  {
>>>       struct s3c64xx_spi_driver_data *sdd = data;
>>>       struct spi_master *spi = sdd->master;
>>> -     unsigned int val;
>>> +     unsigned int val, clr = 0;
>>>
>>> -     val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>> +     val = readl(sdd->regs + S3C64XX_SPI_STATUS);
>>>
>>> -     val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
>>> -             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
>>> -             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
>>> -             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>> -
>>> -     writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>> -
>>> -     if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
>>> +     if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
>>> +             clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
>>>               dev_err(&spi->dev, "RX overrun\n");
>>> -     if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
>>> +     }
>>> +     if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
>>> +             clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
>>>               dev_err(&spi->dev, "RX underrun\n");
>>> -     if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
>>> +     }
>>> +     if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
>>> +             clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
>>>               dev_err(&spi->dev, "TX overrun\n");
>>> -     if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
>>> +     }
>>> +     if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
>>> +             clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>>               dev_err(&spi->dev, "TX underrun\n");
>>> +     }
>>> +
>>> +     /* Clear the pending irq by setting and then clearing it */
>>> +     writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>> +     writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>
>> Wait, what?  clr & ~clr == 0   Always.  What are you actually trying to do here?
> The user manual says, wirting 1 to the pending clear register clears
> the interrupt (its not auto clear to 0). so i need to explicitly reset
> those bits thats what the 2nd write does

Then write 0. That's the result of what the code does anyway, but the
code as-written is nonsensical.

g.

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girishks2000@gmail.com Feb. 7, 2013, 12:33 a.m. UTC | #4
On Wed, Feb 6, 2013 at 3:48 PM, Grant Likely <grant.likely@secretlab.ca> wrote:
> On Wed, Feb 6, 2013 at 8:12 PM, Girish KS <girishks2000@gmail.com> wrote:
>> On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely <grant.likely@secretlab.ca> wrote:
>>> On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S <girishks2000@gmail.com> wrote:
>>>> The status of the interrupt is available in the status register,
>>>> so reading the clear pending register and writing back the same
>>>> value will not actually clear the pending interrupts. This patch
>>>> modifies the interrupt handler to read the status register and
>>>> clear the corresponding pending bit in the clear pending register.
>>>>
>>>> Modified the hwInit function to clear all the pending interrupts.
>>>>
>>>> Signed-off-by: Girish K S <ks.giri@samsung.com>
>>>> ---
>>>>  drivers/spi/spi-s3c64xx.c |   41 +++++++++++++++++++++++++----------------
>>>>  1 file changed, 25 insertions(+), 16 deletions(-)
>>>>
>>>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>>>> index ad93231..b770f88 100644
>>>> --- a/drivers/spi/spi-s3c64xx.c
>>>> +++ b/drivers/spi/spi-s3c64xx.c
>>>> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq, void *data)
>>>>  {
>>>>       struct s3c64xx_spi_driver_data *sdd = data;
>>>>       struct spi_master *spi = sdd->master;
>>>> -     unsigned int val;
>>>> +     unsigned int val, clr = 0;
>>>>
>>>> -     val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>> +     val = readl(sdd->regs + S3C64XX_SPI_STATUS);
>>>>
>>>> -     val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
>>>> -             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
>>>> -             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
>>>> -             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>>> -
>>>> -     writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>> -
>>>> -     if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
>>>> +     if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
>>>> +             clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
>>>>               dev_err(&spi->dev, "RX overrun\n");
>>>> -     if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
>>>> +     }
>>>> +     if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
>>>> +             clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
>>>>               dev_err(&spi->dev, "RX underrun\n");
>>>> -     if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
>>>> +     }
>>>> +     if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
>>>> +             clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
>>>>               dev_err(&spi->dev, "TX overrun\n");
>>>> -     if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
>>>> +     }
>>>> +     if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
>>>> +             clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>>>               dev_err(&spi->dev, "TX underrun\n");
>>>> +     }
>>>> +
>>>> +     /* Clear the pending irq by setting and then clearing it */
>>>> +     writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>> +     writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>
>>> Wait, what?  clr & ~clr == 0   Always.  What are you actually trying to do here?
>> The user manual says, wirting 1 to the pending clear register clears
>> the interrupt (its not auto clear to 0). so i need to explicitly reset
>> those bits thats what the 2nd write does
>
> Then write 0. That's the result of what the code does anyway, but the
> code as-written is nonsensical.
Just writing 0 doest clear the status bit. The status bit in the
status register is cleared only when the corresponding bit in clear
pending register is set.
If not cleared after setting. On the next Interrupt, writing 1 to a
previously set bit will not clear the status bit.
Hope its clear
>
> g.

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Tomasz Figa Feb. 7, 2013, 11:09 a.m. UTC | #5
Hi Girish,

On Wednesday 06 of February 2013 12:12:29 Girish KS wrote:
> On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely <grant.likely@secretlab.ca> 
wrote:
> > On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S 
<girishks2000@gmail.com> wrote:
> >> The status of the interrupt is available in the status register,
> >> so reading the clear pending register and writing back the same
> >> value will not actually clear the pending interrupts. This patch
> >> modifies the interrupt handler to read the status register and
> >> clear the corresponding pending bit in the clear pending register.
> >> 
> >> Modified the hwInit function to clear all the pending interrupts.
> >> 
> >> Signed-off-by: Girish K S <ks.giri@samsung.com>
> >> ---
> >> 
> >>  drivers/spi/spi-s3c64xx.c |   41
> >>  +++++++++++++++++++++++++---------------- 1 file changed, 25
> >>  insertions(+), 16 deletions(-)
> >> 
> >> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
> >> index ad93231..b770f88 100644
> >> --- a/drivers/spi/spi-s3c64xx.c
> >> +++ b/drivers/spi/spi-s3c64xx.c
> >> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq,
> >> void *data)>> 
> >>  {
> >>  
> >>       struct s3c64xx_spi_driver_data *sdd = data;
> >>       struct spi_master *spi = sdd->master;
> >> 
> >> -     unsigned int val;
> >> +     unsigned int val, clr = 0;
> >> 
> >> -     val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
> >> +     val = readl(sdd->regs + S3C64XX_SPI_STATUS);
> >> 
> >> -     val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
> >> -             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
> >> -             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
> >> -             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
> >> -
> >> -     writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
> >> -
> >> -     if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
> >> +     if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
> >> +             clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
> >> 
> >>               dev_err(&spi->dev, "RX overrun\n");
> >> 
> >> -     if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
> >> +     }
> >> +     if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
> >> +             clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
> >> 
> >>               dev_err(&spi->dev, "RX underrun\n");
> >> 
> >> -     if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
> >> +     }
> >> +     if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
> >> +             clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
> >> 
> >>               dev_err(&spi->dev, "TX overrun\n");
> >> 
> >> -     if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
> >> +     }
> >> +     if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
> >> +             clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
> >> 
> >>               dev_err(&spi->dev, "TX underrun\n");
> >> 
> >> +     }
> >> +
> >> +     /* Clear the pending irq by setting and then clearing it */
> >> +     writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
> >> +     writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
> > 
> > Wait, what?  clr & ~clr == 0   Always.  What are you actually trying
> > to do here?
> The user manual says, wirting 1 to the pending clear register clears
> the interrupt (its not auto clear to 0). so i need to explicitly reset
> those bits thats what the 2nd write does

I have looked through user's manuals of different Samsung SoCs. All of 
them said that writing 1 to a bit clears the corresponding interrupt, but 
none of them contain any note that it must be manually cleared to 0.

In addition the expression

clr & ~clr

makes no sense, because it is equal to 0.

If you really need to clear those bits manually (and I don't think so), 
you should replace this expression with 0.

Best regards,
girishks2000@gmail.com Feb. 7, 2013, 5:46 p.m. UTC | #6
On Thu, Feb 7, 2013 at 3:09 AM, Tomasz Figa <t.figa@samsung.com> wrote:
> Hi Girish,
>
> On Wednesday 06 of February 2013 12:12:29 Girish KS wrote:
>> On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely <grant.likely@secretlab.ca>
> wrote:
>> > On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S
> <girishks2000@gmail.com> wrote:
>> >> The status of the interrupt is available in the status register,
>> >> so reading the clear pending register and writing back the same
>> >> value will not actually clear the pending interrupts. This patch
>> >> modifies the interrupt handler to read the status register and
>> >> clear the corresponding pending bit in the clear pending register.
>> >>
>> >> Modified the hwInit function to clear all the pending interrupts.
>> >>
>> >> Signed-off-by: Girish K S <ks.giri@samsung.com>
>> >> ---
>> >>
>> >>  drivers/spi/spi-s3c64xx.c |   41
>> >>  +++++++++++++++++++++++++---------------- 1 file changed, 25
>> >>  insertions(+), 16 deletions(-)
>> >>
>> >> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>> >> index ad93231..b770f88 100644
>> >> --- a/drivers/spi/spi-s3c64xx.c
>> >> +++ b/drivers/spi/spi-s3c64xx.c
>> >> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq,
>> >> void *data)>>
>> >>  {
>> >>
>> >>       struct s3c64xx_spi_driver_data *sdd = data;
>> >>       struct spi_master *spi = sdd->master;
>> >>
>> >> -     unsigned int val;
>> >> +     unsigned int val, clr = 0;
>> >>
>> >> -     val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> >> +     val = readl(sdd->regs + S3C64XX_SPI_STATUS);
>> >>
>> >> -     val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
>> >> -             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
>> >> -             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
>> >> -             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>> >> -
>> >> -     writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> >> -
>> >> -     if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
>> >> +     if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
>> >> +             clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
>> >>
>> >>               dev_err(&spi->dev, "RX overrun\n");
>> >>
>> >> -     if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
>> >> +     }
>> >> +     if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
>> >> +             clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
>> >>
>> >>               dev_err(&spi->dev, "RX underrun\n");
>> >>
>> >> -     if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
>> >> +     }
>> >> +     if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
>> >> +             clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
>> >>
>> >>               dev_err(&spi->dev, "TX overrun\n");
>> >>
>> >> -     if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
>> >> +     }
>> >> +     if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
>> >> +             clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>> >>
>> >>               dev_err(&spi->dev, "TX underrun\n");
>> >>
>> >> +     }
>> >> +
>> >> +     /* Clear the pending irq by setting and then clearing it */
>> >> +     writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> >> +     writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> >
>> > Wait, what?  clr & ~clr == 0   Always.  What are you actually trying
>> > to do here?
>> The user manual says, wirting 1 to the pending clear register clears
>> the interrupt (its not auto clear to 0). so i need to explicitly reset
>> those bits thats what the 2nd write does
>
> I have looked through user's manuals of different Samsung SoCs. All of
> them said that writing 1 to a bit clears the corresponding interrupt, but
> none of them contain any note that it must be manually cleared to 0.
What i meant was the clear pending bit will not clear automatically.
When I set the
clear pending bit, it remains set. This is a problem for the next
interrupt cycle.
> In addition the expression
>
> clr & ~clr
>
> makes no sense, because it is equal to 0.
It makes sense, because we are not disturbing the interrupt pending
bit at position 0, which is a trailing clr bit.
>
> If you really need to clear those bits manually (and I don't think so),
> you should replace this expression with 0.
since we are not enabling (was not enabled in previous implementation)
trailing byte interrupt, and not handling the same in handler
we cannot write 0.

>
> Best regards,
> --
> Tomasz Figa
> Samsung Poland R&D Center
> SW Solution Development, Linux Platform
>

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girishks2000@gmail.com Feb. 8, 2013, 1:04 a.m. UTC | #7
On Wed, Feb 6, 2013 at 3:48 PM, Grant Likely <grant.likely@secretlab.ca> wrote:
> On Wed, Feb 6, 2013 at 8:12 PM, Girish KS <girishks2000@gmail.com> wrote:
>> On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely <grant.likely@secretlab.ca> wrote:
>>> On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S <girishks2000@gmail.com> wrote:
>>>> The status of the interrupt is available in the status register,
>>>> so reading the clear pending register and writing back the same
>>>> value will not actually clear the pending interrupts. This patch
>>>> modifies the interrupt handler to read the status register and
>>>> clear the corresponding pending bit in the clear pending register.
>>>>
>>>> Modified the hwInit function to clear all the pending interrupts.
>>>>
>>>> Signed-off-by: Girish K S <ks.giri@samsung.com>
>>>> ---
>>>>  drivers/spi/spi-s3c64xx.c |   41 +++++++++++++++++++++++++----------------
>>>>  1 file changed, 25 insertions(+), 16 deletions(-)
>>>>
>>>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>>>> index ad93231..b770f88 100644
>>>> --- a/drivers/spi/spi-s3c64xx.c
>>>> +++ b/drivers/spi/spi-s3c64xx.c
>>>> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq, void *data)
>>>>  {
>>>>       struct s3c64xx_spi_driver_data *sdd = data;
>>>>       struct spi_master *spi = sdd->master;
>>>> -     unsigned int val;
>>>> +     unsigned int val, clr = 0;
>>>>
>>>> -     val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>> +     val = readl(sdd->regs + S3C64XX_SPI_STATUS);
>>>>
>>>> -     val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
>>>> -             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
>>>> -             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
>>>> -             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>>> -
>>>> -     writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>> -
>>>> -     if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
>>>> +     if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
>>>> +             clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
>>>>               dev_err(&spi->dev, "RX overrun\n");
>>>> -     if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
>>>> +     }
>>>> +     if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
>>>> +             clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
>>>>               dev_err(&spi->dev, "RX underrun\n");
>>>> -     if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
>>>> +     }
>>>> +     if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
>>>> +             clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
>>>>               dev_err(&spi->dev, "TX overrun\n");
>>>> -     if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
>>>> +     }
>>>> +     if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
>>>> +             clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>>>               dev_err(&spi->dev, "TX underrun\n");
>>>> +     }
>>>> +
>>>> +     /* Clear the pending irq by setting and then clearing it */
>>>> +     writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>> +     writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>
>>> Wait, what?  clr & ~clr == 0   Always.  What are you actually trying to do here?
>> The user manual says, wirting 1 to the pending clear register clears
>> the interrupt (its not auto clear to 0). so i need to explicitly reset
>> those bits thats what the 2nd write does
>
> Then write 0. That's the result of what the code does anyway, but the
> code as-written is nonsensical.
i cannot write 0. because the 0th bit is trailing byte interrupt clear
pending bit, which is not being handled in the handler.
>
> g.

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girishks2000@gmail.com Feb. 8, 2013, 8:16 a.m. UTC | #8
On Thu, Feb 7, 2013 at 5:04 PM, Girish KS <girishks2000@gmail.com> wrote:
> On Wed, Feb 6, 2013 at 3:48 PM, Grant Likely <grant.likely@secretlab.ca> wrote:
>> On Wed, Feb 6, 2013 at 8:12 PM, Girish KS <girishks2000@gmail.com> wrote:
>>> On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely <grant.likely@secretlab.ca> wrote:
>>>> On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S <girishks2000@gmail.com> wrote:
>>>>> The status of the interrupt is available in the status register,
>>>>> so reading the clear pending register and writing back the same
>>>>> value will not actually clear the pending interrupts. This patch
>>>>> modifies the interrupt handler to read the status register and
>>>>> clear the corresponding pending bit in the clear pending register.
>>>>>
>>>>> Modified the hwInit function to clear all the pending interrupts.
>>>>>
>>>>> Signed-off-by: Girish K S <ks.giri@samsung.com>
>>>>> ---
>>>>>  drivers/spi/spi-s3c64xx.c |   41 +++++++++++++++++++++++++----------------
>>>>>  1 file changed, 25 insertions(+), 16 deletions(-)
>>>>>
>>>>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>>>>> index ad93231..b770f88 100644
>>>>> --- a/drivers/spi/spi-s3c64xx.c
>>>>> +++ b/drivers/spi/spi-s3c64xx.c
>>>>> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq, void *data)
>>>>>  {
>>>>>       struct s3c64xx_spi_driver_data *sdd = data;
>>>>>       struct spi_master *spi = sdd->master;
>>>>> -     unsigned int val;
>>>>> +     unsigned int val, clr = 0;
>>>>>
>>>>> -     val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>>> +     val = readl(sdd->regs + S3C64XX_SPI_STATUS);
>>>>>
>>>>> -     val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
>>>>> -             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
>>>>> -             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
>>>>> -             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>>>> -
>>>>> -     writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>>> -
>>>>> -     if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
>>>>> +     if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
>>>>> +             clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
>>>>>               dev_err(&spi->dev, "RX overrun\n");
>>>>> -     if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
>>>>> +     }
>>>>> +     if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
>>>>> +             clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
>>>>>               dev_err(&spi->dev, "RX underrun\n");
>>>>> -     if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
>>>>> +     }
>>>>> +     if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
>>>>> +             clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
>>>>>               dev_err(&spi->dev, "TX overrun\n");
>>>>> -     if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
>>>>> +     }
>>>>> +     if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
>>>>> +             clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>>>>               dev_err(&spi->dev, "TX underrun\n");
>>>>> +     }
>>>>> +
>>>>> +     /* Clear the pending irq by setting and then clearing it */
>>>>> +     writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>>> +     writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>>>
>>>> Wait, what?  clr & ~clr == 0   Always.  What are you actually trying to do here?
>>> The user manual says, wirting 1 to the pending clear register clears
>>> the interrupt (its not auto clear to 0). so i need to explicitly reset
>>> those bits thats what the 2nd write does
>>
>> Then write 0. That's the result of what the code does anyway, but the
>> code as-written is nonsensical.
> i cannot write 0. because the 0th bit is trailing byte interrupt clear
> pending bit, which is not being handled in the handler.

Sorry, Writing 0  will still be valid after code for trainling byte is added..
will change and resubmit

>>
>> g.

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Tomasz Figa Feb. 8, 2013, 8:33 a.m. UTC | #9
On Thursday 07 of February 2013 09:46:58 Girish KS wrote:
> On Thu, Feb 7, 2013 at 3:09 AM, Tomasz Figa <t.figa@samsung.com> wrote:
> > Hi Girish,
> > 
> > On Wednesday 06 of February 2013 12:12:29 Girish KS wrote:
> >> On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely
> >> <grant.likely@secretlab.ca>> 
> > wrote:
> >> > On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S
> > 
> > <girishks2000@gmail.com> wrote:
> >> >> The status of the interrupt is available in the status register,
> >> >> so reading the clear pending register and writing back the same
> >> >> value will not actually clear the pending interrupts. This patch
> >> >> modifies the interrupt handler to read the status register and
> >> >> clear the corresponding pending bit in the clear pending register.
> >> >> 
> >> >> Modified the hwInit function to clear all the pending interrupts.
> >> >> 
> >> >> Signed-off-by: Girish K S <ks.giri@samsung.com>
> >> >> ---
> >> >> 
> >> >>  drivers/spi/spi-s3c64xx.c |   41
> >> >>  +++++++++++++++++++++++++---------------- 1 file changed, 25
> >> >>  insertions(+), 16 deletions(-)
> >> >> 
> >> >> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
> >> >> index ad93231..b770f88 100644
> >> >> --- a/drivers/spi/spi-s3c64xx.c
> >> >> +++ b/drivers/spi/spi-s3c64xx.c
> >> >> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq,
> >> >> void *data)>>
> >> >> 
> >> >>  {
> >> >>  
> >> >>       struct s3c64xx_spi_driver_data *sdd = data;
> >> >>       struct spi_master *spi = sdd->master;
> >> >> 
> >> >> -     unsigned int val;
> >> >> +     unsigned int val, clr = 0;
> >> >> 
> >> >> -     val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
> >> >> +     val = readl(sdd->regs + S3C64XX_SPI_STATUS);
> >> >> 
> >> >> -     val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
> >> >> -             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
> >> >> -             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
> >> >> -             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
> >> >> -
> >> >> -     writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
> >> >> -
> >> >> -     if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
> >> >> +     if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
> >> >> +             clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
> >> >> 
> >> >>               dev_err(&spi->dev, "RX overrun\n");
> >> >> 
> >> >> -     if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
> >> >> +     }
> >> >> +     if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
> >> >> +             clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
> >> >> 
> >> >>               dev_err(&spi->dev, "RX underrun\n");
> >> >> 
> >> >> -     if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
> >> >> +     }
> >> >> +     if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
> >> >> +             clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
> >> >> 
> >> >>               dev_err(&spi->dev, "TX overrun\n");
> >> >> 
> >> >> -     if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
> >> >> +     }
> >> >> +     if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
> >> >> +             clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
> >> >> 
> >> >>               dev_err(&spi->dev, "TX underrun\n");
> >> >> 
> >> >> +     }
> >> >> +
> >> >> +     /* Clear the pending irq by setting and then clearing it */
> >> >> +     writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
> >> >> +     writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
> >> > 
> >> > Wait, what?  clr & ~clr == 0   Always.  What are you actually
> >> > trying
> >> > to do here?
> >> 
> >> The user manual says, wirting 1 to the pending clear register clears
> >> the interrupt (its not auto clear to 0). so i need to explicitly
> >> reset
> >> those bits thats what the 2nd write does
> > 
> > I have looked through user's manuals of different Samsung SoCs. All of
> > them said that writing 1 to a bit clears the corresponding interrupt,
> > but none of them contain any note that it must be manually cleared to
> > 0.
> What i meant was the clear pending bit will not clear automatically.
> When I set the
> clear pending bit, it remains set. This is a problem for the next
> interrupt cycle.

How did you check that it does not clear automatically?

> > In addition the expression
> > 
> > clr & ~clr
> > 
> > makes no sense, because it is equal to 0.
> 
> It makes sense, because we are not disturbing the interrupt pending
> bit at position 0, which is a trailing clr bit.

You either seem to misunderstand the problem I'm mentioning or not 
understanding it at all.

If you take a variable named clr, no matter what value it is set to, and 
you AND it with bitwise negation of the same variable, you will get 0.

See on this example:

Bits:     7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
         -------------------------------
Values:   1 | 1 | 0 | 0 | 1 | 0 | 0 | 1
         -------------------------------
Negation: 0 | 0 | 1 | 1 | 0 | 1 | 1 | 0
         -------------------------------
AND:      0 | 0 | 0 | 0 | 0 | 0 | 0 | 0

Now, can you see that (clr & ~clr) is the same as (0)?

Best regards,
Tomasz


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girishks2000@gmail.com Feb. 8, 2013, 8:58 a.m. UTC | #10
On Fri, Feb 8, 2013 at 12:33 AM, Tomasz Figa <tomasz.figa@gmail.com> wrote:
> On Thursday 07 of February 2013 09:46:58 Girish KS wrote:
>> On Thu, Feb 7, 2013 at 3:09 AM, Tomasz Figa <t.figa@samsung.com> wrote:
>> > Hi Girish,
>> >
>> > On Wednesday 06 of February 2013 12:12:29 Girish KS wrote:
>> >> On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely
>> >> <grant.likely@secretlab.ca>>
>> > wrote:
>> >> > On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S
>> >
>> > <girishks2000@gmail.com> wrote:
>> >> >> The status of the interrupt is available in the status register,
>> >> >> so reading the clear pending register and writing back the same
>> >> >> value will not actually clear the pending interrupts. This patch
>> >> >> modifies the interrupt handler to read the status register and
>> >> >> clear the corresponding pending bit in the clear pending register.
>> >> >>
>> >> >> Modified the hwInit function to clear all the pending interrupts.
>> >> >>
>> >> >> Signed-off-by: Girish K S <ks.giri@samsung.com>
>> >> >> ---
>> >> >>
>> >> >>  drivers/spi/spi-s3c64xx.c |   41
>> >> >>  +++++++++++++++++++++++++---------------- 1 file changed, 25
>> >> >>  insertions(+), 16 deletions(-)
>> >> >>
>> >> >> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>> >> >> index ad93231..b770f88 100644
>> >> >> --- a/drivers/spi/spi-s3c64xx.c
>> >> >> +++ b/drivers/spi/spi-s3c64xx.c
>> >> >> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq,
>> >> >> void *data)>>
>> >> >>
>> >> >>  {
>> >> >>
>> >> >>       struct s3c64xx_spi_driver_data *sdd = data;
>> >> >>       struct spi_master *spi = sdd->master;
>> >> >>
>> >> >> -     unsigned int val;
>> >> >> +     unsigned int val, clr = 0;
>> >> >>
>> >> >> -     val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> >> >> +     val = readl(sdd->regs + S3C64XX_SPI_STATUS);
>> >> >>
>> >> >> -     val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
>> >> >> -             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
>> >> >> -             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
>> >> >> -             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>> >> >> -
>> >> >> -     writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> >> >> -
>> >> >> -     if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
>> >> >> +     if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
>> >> >> +             clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
>> >> >>
>> >> >>               dev_err(&spi->dev, "RX overrun\n");
>> >> >>
>> >> >> -     if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
>> >> >> +     }
>> >> >> +     if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
>> >> >> +             clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
>> >> >>
>> >> >>               dev_err(&spi->dev, "RX underrun\n");
>> >> >>
>> >> >> -     if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
>> >> >> +     }
>> >> >> +     if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
>> >> >> +             clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
>> >> >>
>> >> >>               dev_err(&spi->dev, "TX overrun\n");
>> >> >>
>> >> >> -     if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
>> >> >> +     }
>> >> >> +     if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
>> >> >> +             clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>> >> >>
>> >> >>               dev_err(&spi->dev, "TX underrun\n");
>> >> >>
>> >> >> +     }
>> >> >> +
>> >> >> +     /* Clear the pending irq by setting and then clearing it */
>> >> >> +     writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> >> >> +     writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>> >> >
>> >> > Wait, what?  clr & ~clr == 0   Always.  What are you actually
>> >> > trying
>> >> > to do here?
>> >>
>> >> The user manual says, wirting 1 to the pending clear register clears
>> >> the interrupt (its not auto clear to 0). so i need to explicitly
>> >> reset
>> >> those bits thats what the 2nd write does
>> >
>> > I have looked through user's manuals of different Samsung SoCs. All of
>> > them said that writing 1 to a bit clears the corresponding interrupt,
>> > but none of them contain any note that it must be manually cleared to
>> > 0.
>> What i meant was the clear pending bit will not clear automatically.
>> When I set the
>> clear pending bit, it remains set. This is a problem for the next
>> interrupt cycle.
>
> How did you check that it does not clear automatically?
I checked it with trace32 debugger. Also  confirmed with the IP
validation engineer.
>
>> > In addition the expression
>> >
>> > clr & ~clr
>> >
>> > makes no sense, because it is equal to 0.
>>
>> It makes sense, because we are not disturbing the interrupt pending
>> bit at position 0, which is a trailing clr bit.
>
> You either seem to misunderstand the problem I'm mentioning or not
> understanding it at all.
>
> If you take a variable named clr, no matter what value it is set to, and
> you AND it with bitwise negation of the same variable, you will get 0.
>
> See on this example:
>
> Bits:     7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
>          -------------------------------
> Values:   1 | 1 | 0 | 0 | 1 | 0 | 0 | 1
>          -------------------------------
> Negation: 0 | 0 | 1 | 1 | 0 | 1 | 1 | 0
>          -------------------------------
> AND:      0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
>
> Now, can you see that (clr & ~clr) is the same as (0)?

Already apolozised for the same: will resubmit.

>
> Best regards,
> Tomasz
>

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girishks2000@gmail.com Feb. 8, 2013, 9:26 a.m. UTC | #11
On Fri, Feb 8, 2013 at 12:58 AM, Girish KS <girishks2000@gmail.com> wrote:
> On Fri, Feb 8, 2013 at 12:33 AM, Tomasz Figa <tomasz.figa@gmail.com> wrote:
>> On Thursday 07 of February 2013 09:46:58 Girish KS wrote:
>>> On Thu, Feb 7, 2013 at 3:09 AM, Tomasz Figa <t.figa@samsung.com> wrote:
>>> > Hi Girish,
>>> >
>>> > On Wednesday 06 of February 2013 12:12:29 Girish KS wrote:
>>> >> On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely
>>> >> <grant.likely@secretlab.ca>>
>>> > wrote:
>>> >> > On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S
>>> >
>>> > <girishks2000@gmail.com> wrote:
>>> >> >> The status of the interrupt is available in the status register,
>>> >> >> so reading the clear pending register and writing back the same
>>> >> >> value will not actually clear the pending interrupts. This patch
>>> >> >> modifies the interrupt handler to read the status register and
>>> >> >> clear the corresponding pending bit in the clear pending register.
>>> >> >>
>>> >> >> Modified the hwInit function to clear all the pending interrupts.
>>> >> >>
>>> >> >> Signed-off-by: Girish K S <ks.giri@samsung.com>
>>> >> >> ---
>>> >> >>
>>> >> >>  drivers/spi/spi-s3c64xx.c |   41
>>> >> >>  +++++++++++++++++++++++++---------------- 1 file changed, 25
>>> >> >>  insertions(+), 16 deletions(-)
>>> >> >>
>>> >> >> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>>> >> >> index ad93231..b770f88 100644
>>> >> >> --- a/drivers/spi/spi-s3c64xx.c
>>> >> >> +++ b/drivers/spi/spi-s3c64xx.c
>>> >> >> @@ -997,25 +997,30 @@ static irqreturn_t s3c64xx_spi_irq(int irq,
>>> >> >> void *data)>>
>>> >> >>
>>> >> >>  {
>>> >> >>
>>> >> >>       struct s3c64xx_spi_driver_data *sdd = data;
>>> >> >>       struct spi_master *spi = sdd->master;
>>> >> >>
>>> >> >> -     unsigned int val;
>>> >> >> +     unsigned int val, clr = 0;
>>> >> >>
>>> >> >> -     val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>> >> >> +     val = readl(sdd->regs + S3C64XX_SPI_STATUS);
>>> >> >>
>>> >> >> -     val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
>>> >> >> -             S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
>>> >> >> -             S3C64XX_SPI_PND_TX_OVERRUN_CLR |
>>> >> >> -             S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>> >> >> -
>>> >> >> -     writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>> >> >> -
>>> >> >> -     if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
>>> >> >> +     if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
>>> >> >> +             clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
>>> >> >>
>>> >> >>               dev_err(&spi->dev, "RX overrun\n");
>>> >> >>
>>> >> >> -     if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
>>> >> >> +     }
>>> >> >> +     if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
>>> >> >> +             clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
>>> >> >>
>>> >> >>               dev_err(&spi->dev, "RX underrun\n");
>>> >> >>
>>> >> >> -     if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
>>> >> >> +     }
>>> >> >> +     if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
>>> >> >> +             clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
>>> >> >>
>>> >> >>               dev_err(&spi->dev, "TX overrun\n");
>>> >> >>
>>> >> >> -     if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
>>> >> >> +     }
>>> >> >> +     if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
>>> >> >> +             clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
>>> >> >>
>>> >> >>               dev_err(&spi->dev, "TX underrun\n");
>>> >> >>
>>> >> >> +     }
>>> >> >> +
>>> >> >> +     /* Clear the pending irq by setting and then clearing it */
>>> >> >> +     writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>> >> >> +     writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
>>> >> >
>>> >> > Wait, what?  clr & ~clr == 0   Always.  What are you actually
>>> >> > trying
>>> >> > to do here?
>>> >>
>>> >> The user manual says, wirting 1 to the pending clear register clears
>>> >> the interrupt (its not auto clear to 0). so i need to explicitly
>>> >> reset
>>> >> those bits thats what the 2nd write does
>>> >
>>> > I have looked through user's manuals of different Samsung SoCs. All of
>>> > them said that writing 1 to a bit clears the corresponding interrupt,
>>> > but none of them contain any note that it must be manually cleared to
>>> > 0.
>>> What i meant was the clear pending bit will not clear automatically.
>>> When I set the
>>> clear pending bit, it remains set. This is a problem for the next
>>> interrupt cycle.
>>
>> How did you check that it does not clear automatically?
> I checked it with trace32 debugger. Also  confirmed with the IP
> validation engineer.

To be more clear. When i open the trace32 memory window (start with
SPI register's base address), the RX under run bit is set in the
status register. coz the debugger tries to read from the RX data
register. At that time i forcibly set the clear pending register. Once
i set it. It just remains set until i reset it. I consulted the
validation engineer after i saw this behaviour.

Thank you Thomas, Grant and Mark for you time.

>>
>>> > In addition the expression
>>> >
>>> > clr & ~clr
>>> >
>>> > makes no sense, because it is equal to 0.
>>>
>>> It makes sense, because we are not disturbing the interrupt pending
>>> bit at position 0, which is a trailing clr bit.
>>
>> You either seem to misunderstand the problem I'm mentioning or not
>> understanding it at all.
>>
>> If you take a variable named clr, no matter what value it is set to, and
>> you AND it with bitwise negation of the same variable, you will get 0.
>>
>> See on this example:
>>
>> Bits:     7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
>>          -------------------------------
>> Values:   1 | 1 | 0 | 0 | 1 | 0 | 0 | 1
>>          -------------------------------
>> Negation: 0 | 0 | 1 | 1 | 0 | 1 | 1 | 0
>>          -------------------------------
>> AND:      0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
>>
>> Now, can you see that (clr & ~clr) is the same as (0)?
>
> Already apolozised for the same: will resubmit.
>
>>
>> Best regards,
>> Tomasz
>>

------------------------------------------------------------------------------
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diff mbox

Patch

diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
index ad93231..b770f88 100644
--- a/drivers/spi/spi-s3c64xx.c
+++ b/drivers/spi/spi-s3c64xx.c
@@ -997,25 +997,30 @@  static irqreturn_t s3c64xx_spi_irq(int irq, void *data)
 {
 	struct s3c64xx_spi_driver_data *sdd = data;
 	struct spi_master *spi = sdd->master;
-	unsigned int val;
+	unsigned int val, clr = 0;
 
-	val = readl(sdd->regs + S3C64XX_SPI_PENDING_CLR);
+	val = readl(sdd->regs + S3C64XX_SPI_STATUS);
 
-	val &= S3C64XX_SPI_PND_RX_OVERRUN_CLR |
-		S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
-		S3C64XX_SPI_PND_TX_OVERRUN_CLR |
-		S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
-
-	writel(val, sdd->regs + S3C64XX_SPI_PENDING_CLR);
-
-	if (val & S3C64XX_SPI_PND_RX_OVERRUN_CLR)
+	if (val & S3C64XX_SPI_ST_RX_OVERRUN_ERR) {
+		clr = S3C64XX_SPI_PND_RX_OVERRUN_CLR;
 		dev_err(&spi->dev, "RX overrun\n");
-	if (val & S3C64XX_SPI_PND_RX_UNDERRUN_CLR)
+	}
+	if (val & S3C64XX_SPI_ST_RX_UNDERRUN_ERR) {
+		clr |= S3C64XX_SPI_PND_RX_UNDERRUN_CLR;
 		dev_err(&spi->dev, "RX underrun\n");
-	if (val & S3C64XX_SPI_PND_TX_OVERRUN_CLR)
+	}
+	if (val & S3C64XX_SPI_ST_TX_OVERRUN_ERR) {
+		clr |= S3C64XX_SPI_PND_TX_OVERRUN_CLR;
 		dev_err(&spi->dev, "TX overrun\n");
-	if (val & S3C64XX_SPI_PND_TX_UNDERRUN_CLR)
+	}
+	if (val & S3C64XX_SPI_ST_TX_UNDERRUN_ERR) {
+		clr |= S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
 		dev_err(&spi->dev, "TX underrun\n");
+	}
+
+	/* Clear the pending irq by setting and then clearing it */
+	writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
+	writel(clr & ~clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
 
 	return IRQ_HANDLED;
 }
@@ -1039,9 +1044,13 @@  static void s3c64xx_spi_hwinit(struct s3c64xx_spi_driver_data *sdd, int channel)
 	writel(0, regs + S3C64XX_SPI_MODE_CFG);
 	writel(0, regs + S3C64XX_SPI_PACKET_CNT);
 
-	/* Clear any irq pending bits */
-	writel(readl(regs + S3C64XX_SPI_PENDING_CLR),
-				regs + S3C64XX_SPI_PENDING_CLR);
+	/* Clear any irq pending bits, should set and clear the bits */
+	val = S3C64XX_SPI_PND_RX_OVERRUN_CLR |
+		S3C64XX_SPI_PND_RX_UNDERRUN_CLR |
+		S3C64XX_SPI_PND_TX_OVERRUN_CLR |
+		S3C64XX_SPI_PND_TX_UNDERRUN_CLR;
+	writel(val, regs + S3C64XX_SPI_PENDING_CLR);
+	writel(val & ~val, regs + S3C64XX_SPI_PENDING_CLR);
 
 	writel(0, regs + S3C64XX_SPI_SWAP_CFG);