On Sun, 2011-02-13 at 16:26 -0500, Andy Walls wrote: > On Sun, 2011-02-13 at 13:26 -0700, Mark Zimmerman wrote: > > On Sun, Feb 13, 2011 at 09:52:25AM -0500, Devin Heitmueller wrote: > > > On Sun, Feb 13, 2011 at 9:47 AM, Mark Zimmerman <markzimm@xxxxxxxx> wrote: > > > > Clearly my previous bisection went astray; I think I have a more > > > > sensible result this time. > > > > > > > > qpc$ git bisect good > > > > 44835f197bf1e3f57464f23dfb239fef06cf89be is the first bad commit > > > > commit 44835f197bf1e3f57464f23dfb239fef06cf89be > > > > Author: Jean Delvare <khali@xxxxxxxxxxxx> > > > > Date: ? Sun Jul 18 16:52:05 2010 -0300 > > > > > > > > ? ?V4L/DVB: cx23885: Check for slave nack on all transactions > > > > > > > > ? ?Don't just check for nacks on zero-length transactions. Check on > > > > ? ?other transactions too. > > > > > > This could be a combination of the xc5000 doing clock stretching and > > > the cx23885 i2c master not properly implementing clock stretch. In > > > the past I've seen i2c masters broken in their handling of clock > > > stretching where they treat it as a NAK. > > > > > > The xc5000 being one of the few devices that actually does i2c clock > > > stretching often exposes cases where it is improperly implemented in > > > the i2c master driver (I've had to fix this with several bridges). > > > Devin, I just checked. The CX23885 driver *is* setting up to allow slaves to stretch the clock. By analysis, I have confirmed that Jean's sugguested patch that I moved forward was wrong for the hardware's behavior. When the cx23885 I2C routines decide to set the I2C_EXTEND flag (and maybe the I2C_NOSTOP flag), we most certainly should *not* be expecting an ACK from the particular hardware register. The original commit should certainly be reverted. Checking for slave ACK/NAK will need to be done with a little more care; so for now, I'll settle for ignoring them. Regards, Andy -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
