Hello Moiz,
On Mon, 10 Aug 2009, Sonasath, Moiz wrote:
> I did some analysis and testing of the code with threshold set to zero,
> we cannot make the threshold zero with the present code in place, as
> this would hamper the functionality of the draining feature because in
> this case the XDR interrupt will not be triggered.
>
> XDR-> when TX FIFO level equal/below the XTRSH AND TXSTAT is less than XTRSH
>
> XRDY-> when TX FIFO level equal/below the XTRSH AND TXSTAT is
> equal/greater than XTRSH
>
> This in turn causes XRDY to be triggered always (even when there are
> only last few bytes left to be transmitted) and therefore the code tries
> to transmit data when the upper application is out of data.
Thanks for looking into this. How about just changing
if (dev->fifo_size) {
if (stat & OMAP_I2C_STAT_XRDY)
num_bytes = dev->fifo_size;
else /* read TXSTAT on XDR interrupt */
num_bytes = omap_i2c_read_reg(dev,
OMAP_I2C_BUFSTAT_REG)
& 0x3F;
}
to something like:
if (dev->fifo_size) { /* 2430 and beyond */
if (stat & OMAP_I2C_STAT_XRDY)
num_bytes = clamp(dev->buf_len, 1, dev->fifo_size);
else
num_bytes = omap_i2c_read_reg(dev,
OMAP_I2C_BUFSTAT_REG)
& 0x3F;
}
in the ISR?
The transmit and receive FIFO thresholds should also be split, so the
short transmit FIFO threshold doesn't affect the receive FIFO threshold.
> I checked with the I2C IP team, yes the errata applies to the I2C block
> on OMAP2430 and OMAP2420. I will send out a patch to include OMAP24XX
> for this erratum.
Great, thanks for checking this. Might as well combine it with the same
patch and make it a revision test based on the I2C controller revision
reg.
- Paul
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