On 20-09-08 09:32:32, Felipe Balbi wrote: > > Hi, > > Peter Chen <peter.chen@xxxxxxx> writes: > > At Android ADB and MTP use case, it uses f_fs which supports scatter list, > > it means one request may need several TRBs for it. Besides, TRB consumes > > very fast compared to TRB has prepared for above use case, so we need to > > enlarge the TRB ring length to avoid "no free TRB error". > > can you give a little more detail here? I will. > How many sg entries do you get with ADB? What's the size of each TRB? I remembered it is about 120 requests for ADB and MTP use case, 16KB for each sg entry, so four TRBs (4KB/TRB) per sg entry at worst case. > How many memory does 600 TRBs > actually amount to? How many segments are you using per endpoint? > Each TRB consumes 3 * 32 bits = 12 bytes, 600 TRB consumes 7200 bytes. One segment for each endpoint, one segment includes 600 TRBs. -- Thanks, Peter Chen
