linux-kernel - Re: [PATCH 1/4] spi: s3c64xx: modified error interrupt handling and init

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Message-ID: <CAKrE-KdX+Nxk0X4xdz6Dx3WVtOpV+ms+gPB-Dq-MwZwetyZ5Nw@mail.gmail.com>
Date:	Wed, 6 Feb 2013 12:12:29 -0800
From:	Girish KS <girishks2000@...il.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/4] spi: s3c64xx: modified error interrupt handling and init

On Wed, Feb 6, 2013 at 2:26 AM, Grant Likely <grant.likely@...retlab.ca> wrote:
> On Tue,  5 Feb 2013 15:09:41 -0800, Girish K S <girishks2000@...il.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@...sung.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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