Date: Wed, 27 May 2020 12:39:14 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org>, Konstantin Belousov <kostikbel@gmail.com> Cc: FreeBSD Current <current@FreeBSD.org> Subject: Re: acpi timer reads all ones [Was: efirtc + atrtc at the same time] Message-ID: <da33c67e-7fbd-59cc-a9b3-1b6f24fafeb2@FreeBSD.org> In-Reply-To: <114f788a-3947-0783-5472-173cf3a30d32@FreeBSD.org> References: <021d8df4-a4f8-620d-73b6-b6103d0bf7f1@FreeBSD.org> <199c8845-e42c-fbee-3f13-0b3d0d7234dc@FreeBSD.org> <20200526185528.GA48478@kib.kiev.ua> <b6f5429a-fa0b-3d85-1250-a11807757ef7@FreeBSD.org> <114f788a-3947-0783-5472-173cf3a30d32@FreeBSD.org>
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On 27/05/2020 11:13, Andriy Gapon wrote: > I added more diagnostics and it seems to support the idea that the problem is > related to I/O cycles and bridges. > > ACPI timer suddenly starts returning 0xffffffff and that lasts for tens of > microseconds before the timer goes back to returning normal values with an > expected increase. > AMD provides a proprietary way to access ACPI registers via MMIO (0xfed808xx). > That mechanism is unaffected, ACPI timer register always returns good values. > > The problem seems to happen when restoring configuration of a particular PCI > bridge. What's interesting is that the bridge decodes one memory range and one > I/O range. > > Looking at pci_cfg_restore() I wonder if it is wise to restore PCIR_COMMAND so > early. Could it be that after the resume the bridge is configured with a wrong > I/O range (e.g., too wide) and by writing PCIR_COMMAND we enable that decoding. > So, the bridge steals I/O cycles destined for ACPI support hardware. If there > is nothing behind the bridge to handle those ports, then we get those bad readings. > Once the bridge configuration is fully restored, the I/O handling goes back to > normal. >From what I see, this looks like a BIOS bug. Upon resume, it swaps window configurations of pcib1 and pcib2 (until FreeBSD restores them). pcib1 originally does not have an I/O window. So, BIOS programs both base and limit of pcib2 I/O window to zero. When FreeBSD writes its command register to enable I/O decoding it starts claiming 0x0 - 0xFFF I/O port range. That covers the ACPI ports at 0x8xx. Some printf-s. >From (verbose) boot time: pcib1: domain 0 pcib1: secondary bus 1 pcib1: subordinate bus 1 pcib1: memory decode 0xfea00000-0xfeafffff pcib2: domain 0 pcib2: secondary bus 2 pcib2: subordinate bus 2 pcib2: I/O decode 0xf000-0xffff pcib2: memory decode 0xfe900000-0xfe9fffff My printf-s from resume time: pcib1: old I/O base (low): 0xf1 pcib1: old I/O base (high): 0x0 pcib1: old I/O limit (low): 0x1 pcib1: old I/O limit (high): 0x0 pcib2: old I/O base (low): 0x1 pcib2: old I/O base (high): 0x0 pcib2: old I/O limit (low): 0x1 pcib2: old I/O limit (high): 0x0 -- Andriy Gapon
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