https://bugzilla.kernel.org/show_bug.cgi?id=210351 --- Comment #3 from Johan Hovold (johan@xxxxxxxxxx) --- On Fri, Jan 08, 2021 at 11:37:13AM +0000, bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote: > Unfortunately, I don't have a device at hand right now. But I remember the > lsusb output was showing FT-X type. And under Windows, all three chips I > mentioned work correctly with all prescalers. I contacted FTDI tech support > with this problem. They advised me to have such a patch for ftdi_sio.c and it > solved the problem. Here's the patch: > if ((priv-> chip_type == FT2232C) || (priv-> chip_type == FT2232H) || > > (priv-> chip_type == FT4232H) || (priv-> chip_type == FT232H) || > > (priv-> chip_type == FTX)) { > > / * Probably the BM type needs the MSB of the encoded fractional > > * divider also moved like for the chips above. Any infos? * / > > index = (u16) ((index << 8) | priv-> interface); > > } Ah, that's good to hear. Do you want to submit that as a proper patch that I can apply, or do you want me to do that? > But I don't know why the most significant bit of the prescaler is masked by > something. I have no information about the chip configuration registers. It > looks like this is confidential information. But they could provide it to you > as the driver developer. I don't have access to any details about these chips apart from the public sources either, I'm afraid. But here it seems the upper bits simply needs to be shifted to make room for the interface number just like for the H-types (which can have more than one port). Johan -- You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.
