Re: [PATCH 1/2] spi: pxa2xx: Prepare for edge-triggered interrupts

Jan Kiszka
2017-01-16T11:18:51Z

On 2017-01-16 10:24, Andy Shevchenko wrote:
> On Mon, 2017-01-16 at 10:05 +0100, Jan Kiszka wrote:
>> When using the a device with edge-triggered interrupts, such as MSIs,
>> the interrupt handler has to ensure that there is a point in time
>> during
>> its execution where all interrupts sources are silent so that a new
>> event can trigger a new interrupt again.
>>
>> This is achieved here by looping over SSSR evaluation. We need to take
>> into account that SSCR1 may be changed by the transfer handler, thus
>> we
>> need to redo the mask calculation, at least regarding the volatile
>> interrupt enable bit (TIE).
>
> Could you split this to two patches, one just move the code under
> question to a helper function (no functional change), the other does
> what you state in commit message here?

IMHO, factoring out some helper called from the loop in ssp_int won't be
a natural split due to the large number of local variables being shared
here. But maybe I'm not seeing the design you have in mind, so please
propose a useful helper function signature.

Thanks,
Jan

>
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> ---
>> drivers/spi/spi-pxa2xx.c | 50 +++++++++++++++++++++++++++----------
>> -----------
>> 1 file changed, 28 insertions(+), 22 deletions(-)
>>
>> diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c
>> index dd7b5b4..24bf549 100644
>> --- a/drivers/spi/spi-pxa2xx.c
>> +++ b/drivers/spi/spi-pxa2xx.c
>> @@ -737,6 +737,7 @@ static irqreturn_t ssp_int(int irq, void *dev_id)
>> struct driver_data *drv_data = dev_id;
>> u32 sccr1_reg;
>> u32 mask = drv_data->mask_sr;
>> + irqreturn_t ret = IRQ_NONE;
>> u32 status;
>>
>> /*
>> @@ -760,37 +761,42 @@ static irqreturn_t ssp_int(int irq, void
>> *dev_id)
>>
>> sccr1_reg = pxa2xx_spi_read(drv_data, SSCR1);
>>
>> - /* Ignore possible writes if we don't need to write */
>> - if (!(sccr1_reg & SSCR1_TIE))
>> - mask &= ~SSSR_TFS;
>> -
>> /* Ignore RX timeout interrupt if it is disabled */
>> if (!(sccr1_reg & SSCR1_TINTE))
>> mask &= ~SSSR_TINT;
>>
>> - if (!(status & mask))
>> - return IRQ_NONE;
>> + while (1) {
>> + /* Ignore possible writes if we don't need to write
>> */
>> + if (!(sccr1_reg & SSCR1_TIE))
>> + mask &= ~SSSR_TFS;
>>
>> - if (!drv_data->master->cur_msg) {
>> + if (!(status & mask))
>> + return ret;
>>
>> - pxa2xx_spi_write(drv_data, SSCR0,
>> - pxa2xx_spi_read(drv_data, SSCR0)
>> - & ~SSCR0_SSE);
>> - pxa2xx_spi_write(drv_data, SSCR1,
>> - pxa2xx_spi_read(drv_data, SSCR1)
>> - & ~drv_data->int_cr1);
>> - if (!pxa25x_ssp_comp(drv_data))
>> - pxa2xx_spi_write(drv_data, SSTO, 0);
>> - write_SSSR_CS(drv_data, drv_data->clear_sr);
>> + if (!drv_data->master->cur_msg) {
>>
>> - dev_err(&drv_data->pdev->dev,
>> - "bad message state in interrupt handler\n");
>> + pxa2xx_spi_write(drv_data, SSCR0,
>> + pxa2xx_spi_read(drv_data,
>> SSCR0)
>> + & ~SSCR0_SSE);
>> + pxa2xx_spi_write(drv_data, SSCR1,
>> + pxa2xx_spi_read(drv_data,
>> SSCR1)
>> + & ~drv_data->int_cr1);
>> + if (!pxa25x_ssp_comp(drv_data))
>> + pxa2xx_spi_write(drv_data, SSTO, 0);
>> + write_SSSR_CS(drv_data, drv_data->clear_sr);
>>
>> - /* Never fail */
>> - return IRQ_HANDLED;
>> - }
>> + dev_err(&drv_data->pdev->dev,
>> + "bad message state in interrupt
>> handler\n");
>>
>> - return drv_data->transfer_handler(drv_data);
>> + /* Never fail */
>> + return IRQ_HANDLED;
>> + }
>> +
>> + ret |= drv_data->transfer_handler(drv_data);
>> +
>> + status = pxa2xx_spi_read(drv_data, SSSR);
>> + sccr1_reg = pxa2xx_spi_read(drv_data, SSCR1);
>> + }
>> }
>>
>> /*
>

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