Hi, On 21/08/2014 07:02, Marek Vasut wrote: > On Thursday, August 21, 2014 at 06:11:16 AM, Ye Li wrote: >> The TDAR bit is set when the descriptors are all out from TX ring, but the >> descriptor properly is in transmitting not READY. > > I don't quite understand this, can you please rephrase ? > >> These are two signals, >> and in Ic simulation, we found the TDAR always clear prior than the READY >> bit of last BD. In mx6solox, we use a latest version of FEC IP. It looks >> the intrinsic behave of TDAR bit is changed in this FEC version, not any >> bug in mx6sx. > > OK, so this behavior is isolated to MX6SX and newer. Then any adjustment > should > focus solely on MX6SX and newer.
Not really. It looks like that the implementation is suitable for current FEC IP, but this does not mean that is correct at all. A solution working for all FEC IP versions is surely preferable. > >> There are some solutions for this problem. Which would be acceptable? >> 1. Change the TDAR polling to checking the READY bit in BD. > > This would return the cache-grinding, so this is not nice. > Agree. >> 2. Add polling the READY bit of BD after the TDAR polling. > > If this would be isolated to MX6SX only, then that is doable. > Why not ? On current FEC IP (not MX6SX), this costs only one read of the BD register. Only by MX6SX is polled again. This looks to me the best solution. >> 3. Add a delay after the TDAR polling. > > This is just work. Of course, but it is a trick and we have to add some magical number of uSec, explaining that with "so it works". My preference goes to 2. Best regards, Stefano Babic -- ===================================================================== DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: +49-8142-66989-53 Fax: +49-8142-66989-80 Email: sba...@denx.de ===================================================================== _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
