Hi Laurent,
On Wed, Jan 8, 2014 at 1:27 AM, Laurent Pinchart
<[email protected]> wrote:
> On Tuesday 07 January 2014 21:27:18 Geert Uytterhoeven wrote:
>> I was regularly getting I/O errors when using the Renesas RSPI/QSPI
>> driver on r8a7791:
>>
>> m25p80 spi0.0: error -110 reading SR
>>
>> Until I applied the following patch, which re-reads RSPI_SPSR on a time-out,
>> and continues if the condition has become true:
>>
>> diff --git a/drivers/spi/spi-rspi.c b/drivers/spi/spi-rspi.c
>> index 4b31d89e8568..e63e30c500da 100644
>> --- a/drivers/spi/spi-rspi.c
>> +++ b/drivers/spi/spi-rspi.c
>> @@ -442,8 +442,13 @@ static int rspi_wait_for_interrupt(struct rspi_data
>> *rspi, u8 wait_mask, rspi->spsr = rspi_read8(rspi, RSPI_SPSR);
>> rspi_enable_irq(rspi, enable_bit);
>> ret = wait_event_timeout(rspi->wait, rspi->spsr & wait_mask, HZ);
>> - if (ret == 0 && !(rspi->spsr & wait_mask))
>> - return -ETIMEDOUT;
>> + if (ret == 0 && !(rspi->spsr & wait_mask)) {
>> + u8 spsr = rspi_read8(rspi, RSPI_SPSR);
>> + printk("*** rspi->spsr = 0x%02x, real spsr = 0x%02x, wait_mask
>> =
> 0x%02x
>> ***\n",
>> + rspi->spsr, spsr, wait_mask);
>> + if (!(spsr & wait_mask))
>> + return -ETIMEDOUT;
>> + }
>>
>> return 0;
>> }
>>
>> Now it prints from time to time:
>>
>> *** rspi->spsr = 0x20, real spsr = 0xa0, wait_mask = 0x80 ***
>>
>> which shows that rspi->spsr (as set from the interrupt handler) didn't
>> have bit 7 set, while RSPI_SPSR does have bit 7 set.
>>
>> So this looks like a race condition in the interrupt handling.
>
> What happens if you print rspi->spsr in the interrupt handler ? Does it have
> bit 7 set ?
I haven't tried that yet. The driver is extremely interrupt-heavy (O(n),
with n the number of bytes transfered), so adding a printk() as-is won't be
a good idea.
Will think a bit more about a better approach...
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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