Re: [PATCH 2/2] i2c-mxs: fixed PIO NACK error instead of timeout

["Janusz Użycki" <j.uzycki-9tnw74Q4ehaHKKo6LODCOg@public.gmane.org>]

W dniu 2014-09-08 20:33, Marek Vasut pisze:
> On Monday, September 08, 2014 at 08:06:12 PM, Janusz Użycki wrote:
>> Subject: [PATCH 2/2] i2c-mxs: fixed PIO NACK error instead of timeout
>>    (1000ms)
>>
>> i2cdetect scanned i2c bus very slow if address was not occupied by any
>> device.
> Shouldn't this check be used only after the 'SELECT' command ?
It looks |||mxs_i2c_isr()| for DMA transfer does not differentiate 
commands also
and does not mask irqs for each command.

|STAT_GOT_A_NAK|  is a separate bit.|CTRL1_NO_SLAVE_ACK_IRQ can be set
both after SELECT and WRITE command. Should we differentiate?
|

|Checking CTRL1_NO_SLAVE_ACK_IRQ |bit for SELECT command will increase 
code size only
without special profit. Current PIO implementation also gathers all errors
together and reads them on the end by mxs_i2c_pio_check_error_state().
Probably mxs_i2c_pio_check_error_state() call or
enabling interrupt masks for PIO could be better than
direct |CTRL1_NO_SLAVE_ACK_IRQ |bit checking for clear code.
It also could support multimaster for PIO (MASTER_LOSS).

best regards
Janusz

Signed-off-by: Janusz Uzycki <j.uzycki-9tnw74Q4ehaHKKo6LODCOg@public.gmane.org>
---
   drivers/i2c/busses/i2c-mxs.c | 3 +++
   1 file changed, 3 insertions(+)

diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c
index 87ee72d..b498708 100644
--- a/drivers/i2c/busses/i2c-mxs.c
+++ b/drivers/i2c/busses/i2c-mxs.c
@@ -307,6 +307,9 @@ static int mxs_i2c_pio_wait_xfer_end(struct
mxs_i2c_dev *i2c)
          unsigned long timeout = jiffies + msecs_to_jiffies(1000);

          while (readl(i2c->regs + MXS_I2C_CTRL0) & MXS_I2C_CTRL0_RUN) {
+               /*int ret = mxs_i2c_pio_check_error_state(i2c);*/
+               if (readl(i2c->regs + MXS_I2C_CTRL1) & MXS_I2C_CTRL1_NO_SLAVE_ACK_IRQ)
+                       return -ENXIO;
                  if (time_after(jiffies, timeout))
                          return -ETIMEDOUT;
                  cond_resched();
--
1.7.11.3