Re: [PATCH] SPCR: check bit width for the 16550 UART

From: Duc Dang
Date: Mon Dec 05 2016 - 22:56:19 EST

On Mon, Dec 5, 2016 at 6:27 PM, Jon Masters <jcm@xxxxxxxxxx> wrote:
> Hi Duc, all,
>
> So after regenerating the initrd override (I must have fat fingered)
> it is now detecting the correct bit width on boot (attached dmesg log).
>
> HOWEVER while the console does come up, the use of "earlycon" on the
> command line (with no parameters) doesn't result in the early SPCR
> console coming up correctly. I see some garbled characters that
> suggest the baud (or register access width) is off somewhere.

My bad that I did not catch this in the morning. Yes, earlycon does
not seems to work as expected. I can see that earlycon parameters
seems to be correct, but the bootconsole message does not come out
(the following is from 'dmesg')
[ 0.000000] Booting Linux on physical CPU 0x0
[ 0.000000] Linux version 4.9.0-rc7-next-20161202-00001-gbf2919a
(dhdang@dhdang-workstation-01) (gcc version 4.9.3 20150218
(prerelease) (APM-8.0.10-le) ) #10 SMP PREEMPT Mon Dec 5 19:21:14 PST
2016
[ 0.000000] Boot CPU: AArch64 Processor [500f0001]
[ 0.000000] efi: Getting EFI parameters from FDT:
[ 0.000000] efi: EFI v2.40 by X-Gene Mustang Board EFI Oct 17 2016 13:54:05
[ 0.000000] efi: ACPI=0x47fa700000 ACPI 2.0=0x47fa700014 SMBIOS
3.0=0x47fa9db000 ESRT=0x47ff006d18
[ 0.000000] esrt: Reserving ESRT space from 0x00000047ff006d18 to
0x00000047ff006d78.
[ 0.000000] cma: Reserved 16 MiB at 0x00000040ff000000
[ 0.000000] ACPI: Early table checksum verification disabled
[ 0.000000] ACPI: RSDP 0x00000047FA700014 000024 (v02 APM )
[ 0.000000] ACPI: XSDT 0x00000047FA6F00E8 000084 (v01 APM XGENE
00000003 01000013)
[ 0.000000] ACPI: FACP 0x00000047FA6C0000 00010C (v05 APM XGENE
00000003 INTL 20140724)
[ 0.000000] ACPI: DSDT 0x00000047FA6D0000 005922 (v05 APM
APM88xxx 00000001 INTL 20140724)
[ 0.000000] ACPI: DBG2 0x00000047FA6E0000 0000AA (v00 APMC0D
XGENEDBG 00000000 INTL 20140724)
[ 0.000000] ACPI: GTDT 0x00000047FA6A0000 000060 (v02 APM XGENE
00000001 INTL 20140724)
[ 0.000000] ACPI: MCFG 0x00000047FA690000 00003C (v01 APM XGENE
00000002 INTL 20140724)
[ 0.000000] ACPI: SPCR 0x00000047FA680000 000050 (v02 APMC0D
XGENESPC 00000000 INTL 20140724)
[ 0.000000] ACPI: SSDT 0x00000047FA670000 00002D (v02 APM XGENE
00000001 INTL 20140724)
[ 0.000000] ACPI: BERT 0x00000047FA660000 000030 (v01 APM XGENE
00000002 INTL 20140724)
[ 0.000000] ACPI: HEST 0x00000047FA650000 0002A8 (v01 APM XGENE
00000002 INTL 20140724)
[ 0.000000] ACPI: APIC 0x00000047FA640000 0002A4 (v03 APM XGENE
00000003 01000013)
[ 0.000000] ACPI: SSDT 0x00000047FA630000 000063 (v02 REDHAT
MACADDRS 00000001 01000013)
[ 0.000000] ACPI: SSDT 0x00000047FA620000 000032 (v02 REDHAT
UARTCLKS 00000001 01000013)
[ 0.000000] ACPI: PCCT 0x00000047FA610000 000300 (v01 APM XGENE
00000003 01000013)
[ 0.000000] ACPI: SPCR: console: uart,mmio32,0x1c020000,115200
[ 0.000000] earlycon: uart0 at MMIO32 0x000000001c020000 (options '115200')
[ 0.000000] bootconsole [uart0] enabled

>
> Here are the first few lines from my screen boot log:
>
> EFI stub: Using DTB from configuration table
> EFI stub: Exiting boot services and installing virtual address map...
> ^E^B^B^B<8A>r<A2><92><A2><92>Ê<EA><81>console [ttyS0] enabled

I do not see garbage characters on Mustang. The garbage characters you
saw may relate to the same issue that I asked a few weeks ago:
https://www.spinics.net/lists/arm-kernel/msg537958.html
There seems to be a race condition in accessing the UART hardware
during switching between the bootconsole and the real console.

> [ 1.424297] console [ttyS0] enabled
> [ 1.507860] bootconsole [uart0] disabled
>
> Can you double check you've actually seen the SPCR used for earlycon,
> as the machine was booting, and actually generating correct output?
>
> Here's the SPCR override I am using on that machine:
>
> /*
> * Intel ACPI Component Architecture
> * AML/ASL+ Disassembler version 20160527-64
> * Copyright (c) 2000 - 2016 Intel Corporation
> *
> * Disassembly of SPCR.aml, Sat Dec 3 03:49:54 2016
> *
> * ACPI Data Table [SPCR]
> *
> * Format: [HexOffset DecimalOffset ByteLength] FieldName : FieldValue
> */
>
> [000h 0000 4] Signature : "SPCR" [Serial Port Console Redirection table]
> [004h 0004 4] Table Length : 00000050
> [008h 0008 1] Revision : 02
> [009h 0009 1] Checksum : 41
> [00Ah 0010 6] Oem ID : "HPE "
> [010h 0016 8] Oem Table ID : "ProLiant"
> [018h 0024 4] Oem Revision : 00001337
> [01Ch 0028 4] Asl Compiler ID : "INTL"
> [020h 0032 4] Asl Compiler Revision : 20160527
>
> [024h 0036 1] Interface Type : 00
> [025h 0037 3] Reserved : 000000
>
> [028h 0040 12] Serial Port Register : [Generic Address Structure]
> [028h 0040 1] Space ID : 00 [SystemMemory]
> [029h 0041 1] Bit Width : 20
> [02Ah 0042 1] Bit Offset : 00
> [02Bh 0043 1] Encoded Access Width : 00 [Undefined/Legacy]
> [02Ch 0044 8] Address : 000000001C021000
>
> [034h 0052 1] Interrupt Type : 08
> [035h 0053 1] PCAT-compatible IRQ : 00
> [036h 0054 4] Interrupt : 0000006D
> [03Ah 0058 1] Baud Rate : 03
> [03Bh 0059 1] Parity : 00
> [03Ch 0060 1] Stop Bits : 01
> [03Dh 0061 1] Flow Control : 02
> [03Eh 0062 1] Terminal Type : 01
> [04Ch 0076 1] Reserved : 00
> [040h 0064 2] PCI Device ID : FFFF
> [042h 0066 2] PCI Vendor ID : FFFF
> [044h 0068 1] PCI Bus : 00
> [045h 0069 1] PCI Device : 00
> [046h 0070 1] PCI Function : 00
> [047h 0071 4] PCI Flags : 00000000
> [04Bh 0075 1] PCI Segment : 00
> [04Ch 0076 4] Reserved : 00000000
>
> Raw Table Data: Length 80 (0x50)
>
> 0000: 53 50 43 52 50 00 00 00 02 41 48 50 45 4A 43 4D // SPCRP....AHPEJCM
> 0010: 50 72 6F 4C 69 61 6E 74 01 00 00 00 49 4E 54 4C // ProLiant....INTL
> 0020: 27 05 16 20 0D 00 00 00 00 08 00 00 00 10 02 1C // '.. ............
> 0030: 00 00 00 00 08 00 6D 00 00 00 03 00 01 02 01 00 // ......m.........
> 0040: FF FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00 // ................
>
> Jon.
>
> --
> Computer Architect | Sent from my Fedora powered laptop
>
Regards,
Duc Dang.