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Diffstat (limited to 'results/scraper/launchpad-without-comments/1905226')
| -rw-r--r-- | results/scraper/launchpad-without-comments/1905226 | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/results/scraper/launchpad-without-comments/1905226 b/results/scraper/launchpad-without-comments/1905226 new file mode 100644 index 000000000..4251c0531 --- /dev/null +++ b/results/scraper/launchpad-without-comments/1905226 @@ -0,0 +1,15 @@ +intel-hda: stream reset bits are broken + +From HD audio spec, section 3.3.35: + +"Stream Reset (SRST): Writing a 1 causes the corresponding stream to be reset. [...] After the stream hardware has completed sequencing into the reset state, it will report a 1 in this bit. Software must read a 1 from this bit to verify that the stream is in reset. Writing a 0 causes the corresponding stream to exit reset. When the stream hardware is ready to begin operation, it will report a 0 in this bit. Software must read a 0 from this bit before accessing any of the stream registers." + +So to reset a stream I set the bit, but it never reads back as 1 so the driver either times out or will hang forever waiting for it to become 1. I looked into why this happens and found that as of the latest version (8110fa1), in function intel_hda_set_st_ctl() of the https://github.com/qemu/qemu/blob/master/hw/audio/intel-hda.c, + + if (st->ctl & 0x01) { + /* reset */ + dprint(d, 1, "st #%d: reset\n", reg->stream); + st->ctl = SD_STS_FIFO_READY << 24; + } + +This causes the bit to immediately become set to 0 even if I write a 1, and clearly does not meet the spec. I checked behaviour of real hardware and it works as expected, i.e. I see the bit will become 1 and 0 when I write to it. \ No newline at end of file |