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

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Message-ID: <CAKrE-KfvywLa4xTwCGzan9OfevzBdY8Z2EO2Mc2VaFm5y0XEzg@mail.gmail.com>
Date:	Thu, 7 Feb 2013 17:04:08 -0800
From:	Girish KS <girishks2000@...il.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	spi-devel-general@...ts.sourceforge.net,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.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 3:48 PM, Grant Likely <grant.likely@...retlab.ca> wrote:
> On Wed, Feb 6, 2013 at 8:12 PM, Girish KS <girishks2000@...il.com> wrote:
>> 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
>
> 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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