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Message-ID: <56F16DC2.7030901@hurleysoftware.com>
Date: Tue, 22 Mar 2016 09:07:30 -0700
From: Peter Hurley <peter@...leysoftware.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>,
Aleksey Makarov <aleksey.makarov@...aro.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J . Wysocki" <rjw@...ysocki.net>,
Len Brown <lenb@...nel.org>,
"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
Russell King <linux@....linux.org.uk>,
Leif Lindholm <leif.lindholm@...aro.org>,
Graeme Gregory <graeme.gregory@...aro.org>,
Al Stone <ahs3@...hat.com>,
Christopher Covington <cov@...eaurora.org>,
Yury Norov <ynorov@...iumnetworks.com>,
"Zheng, Lv" <lv.zheng@...el.com>, Jiri Slaby <jslaby@...e.com>
Subject: Re: [PATCH v5 3/6] ACPI: parse SPCR and enable matching console
On 03/22/2016 04:09 AM, Andy Shevchenko wrote:
> On Tue, Mar 22, 2016 at 12:46 PM, Aleksey Makarov
> <aleksey.makarov@...aro.org> wrote:
>> 'ARM Server Base Boot Requiremets' [1] mentions SPCR (Serial Port
>> Console Redirection Table) [2] as a mandatory ACPI table that
>> specifies the configuration of serial console.
>>
>> Parse this table, setup earlycon and enable the specified console.
>>
>> Thanks to Peter Hurley for explaining how this should work.
>>
>> [1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0044a/index.html
>> [2] https://msdn.microsoft.com/en-us/library/windows/hardware/dn639132(v=vs.85).aspx
>>
>
>> +++ b/drivers/acpi/spcr.c
>> @@ -0,0 +1,102 @@
>> +/*
>> + * Copyright (c) 2012, Intel Corporation
>> + * Copyright (c) 2015, Red Hat, Inc.
>> + * Copyright (c) 2015, 2016 Linaro Ltd.
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + */
>> +
>> +#define pr_fmt(fmt) "ACPI: SPCR: " fmt
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/console.h>
>> +#include <linux/kernel.h>
>> +#include <linux/serial_core.h>
>> +
>> +static bool init_earlycon;
>> +
>> +void __init init_spcr_earlycon(void)
>> +{
>> + init_earlycon = true;
>> +}
>> +
>> +int __init parse_spcr(void)
>> +{
>> + static char opts[64];
>> + struct acpi_table_spcr *table;
>> + acpi_size table_size;
>> + acpi_status status;
>> + char *uart;
>> + char *iotype;
>> + int baud_rate;
>> + int err = 0;
>> +
>> + status = acpi_get_table_with_size(ACPI_SIG_SPCR, 0,
>> + (struct acpi_table_header **)&table,
>> + &table_size);
>> +
>> + if (ACPI_FAILURE(status))
>> + return -ENOENT;
>> +
>> + if (table->header.revision < 2) {
>> + err = -EINVAL;
>> + pr_err("wrong table version\n");
>> + goto done;
>> + }
>> +
>> + iotype = (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) ?
>> + "mmio" : "io";
>> +
>> + switch (table->interface_type) {
>> + case ACPI_DBG2_ARM_SBSA_32BIT:
>> + iotype = "mmio32";
>> + /* fall through */
>> + case ACPI_DBG2_ARM_PL011:
>> + case ACPI_DBG2_ARM_SBSA_GENERIC:
>> + case ACPI_DBG2_BCM2835:
>> + uart = "pl011";
>> + break;
>> + case ACPI_DBG2_16550_COMPATIBLE:
>> + case ACPI_DBG2_16550_SUBSET:
>> + uart = "uart";
>> + break;
>> + default:
>> + err = -ENOENT;
>> + goto done;
>> + }
>> +
>> + switch (table->baud_rate) {
>> + case 3:
>> + baud_rate = 9600;
>> + break;
>> + case 4:
>> + baud_rate = 19200;
>> + break;
>> + case 6:
>> + baud_rate = 57600;
>> + break;
>> + case 7:
>> + baud_rate = 115200;
>> + break;
>> + default:
>> + err = -ENOENT;
>> + goto done;
>> + }
>> +
>> + sprintf(opts, "%s,%s,0x%llx,%d", uart, iotype,
>> + table->serial_port.address, baud_rate);
>
> You may use snprintf(), though my question here what would happen on
> 32-bit kernel when you supply 64-bit address as an option?
Yeah this should probably use %pa for the printf specifier.
But note this exposes underlying bug in the earlycon support, because
that was originally written without 32/64-mixed bitness in mind; ie.,
the address is parsed and handled as unsigned long in most places.
>> +
>> + pr_info("console: %s", opts);
>> +
>> + if (init_earlycon)
>> + setup_earlycon(opts);
>> +
>> + err = add_preferred_console(uart, 0, opts + strlen(uart) + 1);
>> +
>> +done:
>> + early_acpi_os_unmap_memory((void __iomem *)table, table_size);
>> + return err;
>> +}
>> diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
>> index d217366..ec030c9 100644
>> --- a/drivers/tty/serial/earlycon.c
>> +++ b/drivers/tty/serial/earlycon.c
>> @@ -22,6 +22,7 @@
>> #include <linux/sizes.h>
>> #include <linux/of.h>
>> #include <linux/of_fdt.h>
>> +#include <linux/acpi.h>
>>
>> #ifdef CONFIG_FIX_EARLYCON_MEM
>> #include <asm/fixmap.h>
>> @@ -206,11 +207,15 @@ static int __init param_setup_earlycon(char *buf)
>> int err;
>>
>> /*
>> - * Just 'earlycon' is a valid param for devicetree earlycons;
>> - * don't generate a warning from parse_early_params() in that case
>> + * Just 'earlycon' is a valid param for devicetree and ACPI SPCR
>> + * earlycons; don't generate a warning from parse_early_params()
>> + * in that case
>> */
>> - if (!buf || !buf[0])
>> - return early_init_dt_scan_chosen_serial();
>> + if (!buf || !buf[0]) {
>> + init_spcr_earlycon();
>
>> + early_init_dt_scan_chosen_serial();
>> + return 0;
>
> And you hide an error?
Well, this is a little bit tricky because "earlycon" early parameter with
missing /chosen/stdout-path node is no longer an error, since ACPI may be
specifying the earlycon instead.
Regards,
Peter Hurley
>> + }
>>
>> err = setup_earlycon(buf);
>> if (err == -ENOENT || err == -EALREADY)
>
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