Re: [PATCH V7 3/5] i2c: tegra: Add DMA Support

[Dmitry Osipenko <digetx@gmail.com>]

В Thu, 31 Jan 2019 03:34:59 +0000
Sowjanya Komatineni <skomatineni@nvidia.com> пишет:

> > I2C_INT_ALL_PACKETS_XFER_COMPLETE shall be masked for the PIO mode
> > I2C_INT_PACKET_XFER_COMPLETE shall be masked for the DMA mode, if
> > I'm not missing something. 
> for packets with repeated start or continue xfer,
> PACKET_XFER_COMPLETE will be triggers for packets with stop bit, both
> PACKET_XFER_COMPLETE and ALL_PACKET_XFER_COMPLETE will be triggered.
> To be align with what PIO mode is doing, will not use
> ALL_PACKETS_XFER_COMPLETE for DMA in next version. 

Sounds good.

> >
> > Handle the error-case here:
> >
> >	if (i2c_dev->msg_err != I2C_ERR_NONE) {
> >		dev_err(i2c_dev->dev, "i2c dma transfer failed\n");
> >		goto i2c_recover;
> >	}
> >
> >...
> >	<--- end of tegra_i2c_xfer_msg() -->
> >
> >	if (likely(i2c_dev->msg_err == I2C_ERR_NONE))
> >		return 0;
> >
> > i2c_recover:
> >	tegra_i2c_init(i2c_dev);
> >	/* start recovery upon arbitration loss in single master
> >	mode */ if (i2c_dev->msg_err == I2C_ERR_ARBITRATION_LOST) {
> >		if (!i2c_dev->is_multimaster_mode)
> >			return tegra_i2c_issue_bus_clear(i2c_dev);
> >		return -EAGAIN;
> >	}
> >	if (i2c_dev->msg_err == I2C_ERR_NO_ACK) {
> >		if (msg->flags & I2C_M_IGNORE_NAK)
> >			return 0;
> >		return -EREMOTEIO;
> >	}
> >
> >	return -EIO;  
> 
> When DMA transfer timeout, no need to check for ARB LOST or NO_ACK as
> if any of those interrupts trigger interrupt handler will terminate
> dmaengine and completes so DMA timeout will not be seen in those
> cases and falls thru msg_err check
> 

Okay.