id = 1618
title = "intel-hda:  SD_STS different behavior for byte write vs. word write"
state = "opened"
created_at = "2023-04-24T19:55:27.817Z"
closed_at = "n/a"
labels = ["Audio"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/1618"
host-os = "Linux"
host-arch = "x86"
qemu-version = "8.0.0"
guest-os = "Fuchsia"
guest-arch = "x86"
description = """The Intel HDA SD_STS register is accessible two different ways in QEMU:  either it's the top 8 bits of a 32-bit access
or it's directly accessible as a byte.
On reads, the register behavior for SD_STS is identical whether accessed as a 32-bit read or an 8-bit read.
On writes, the behavior is different; when written to as an 8-bit write, the BCIS, FIFOE, and DESE bits implement the documented HDA behavior of RW1C (writing a 1 to a bit clears it).  When written to as the top 8 bits of a 32-bit write, writing a 1 to a bit sets the bit -- so an attempt to clear a status bit instead unconditionally sets the status bit."""
reproduce = """1.  Write 32 bits at SD_CTL address with bit 27 set (FIFOE).  This should clear FIFOE, but does not.
2.  Read back SD_STS (SD_CTL address + 3) as a byte.  The FIFOE bit will be set.
3.  Write 8 bits at SD_STS address with bit 3 set (FIFOE).  This should clear FIFOE, and it does.
4.  Read back SD_STS as a byte.  The FIFOE bit will be cleared."""
additional = """"""