linux-kernel - Re: [RFC v2 3/4] ACPI: DBG2: add 16550 UART with 32-bit access

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Date:   Tue, 6 Dec 2016 16:15:43 -0500 (EST)
From:   Jon Masters <jcm@...hat.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Aleksey Makarov <aleksey.makarov@...aro.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Russell King <linux@....linux.org.uk>,
        Peter Hurley <peter@...leysoftware.com>,
        Mark Salter <msalter@...hat.com>, Duc Dang <dhdang@....com>,
        Rob Herring <robh@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        Lv Zheng <lv.zheng@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>,
        "devel@...ica.org" <devel@...ica.org>
Subject: Re: [RFC v2 3/4] ACPI: DBG2: add 16550 UART with 32-bit access

Quick note - specifically, Rafael, this is not currently part of the SPCR specification and should not be considered for inclusion in Linux until that is decided. Once it is determined what the fix for SPCR is, that should then be driven into the component architecture and proposed here.

-- 
Computer Architect | Sent from my 64-bit #ARM Powered phone

> On Dec 6, 2016, at 16:00, Rafael J. Wysocki <rafael@...nel.org> wrote:
> 
> On Tue, Dec 6, 2016 at 6:58 PM, Aleksey Makarov
> <aleksey.makarov@...aro.org> wrote:
>> It was suggested to add a new Microsoft Debug Port Table 2
>> (DBG2) (the table used to enumerate the various subtypes of serial
>> port covered by the SPCR) 16550 UART subtype that may be needed for
>> some additional platforms, such as those based upon AppliedMicro
>> X-Gene ARMv8 SoCs.  This new subtype would be 16550-compatible
>> with 32-bit access.  There already exists 32-bit variant
>> ACPI_DBG2_ARM_SBSA_32BIT of SBSA console ACPI_DBG2_ARM_SBSA_GENERIC.
>> 
>> This patch introduces it to Linux kernel.
>> 
>> Signed-off-by: Aleksey Makarov <aleksey.makarov@...aro.org>
>> ---
>> include/acpi/actbl2.h | 1 +
>> 1 file changed, 1 insertion(+)
>> 
>> diff --git a/include/acpi/actbl2.h b/include/acpi/actbl2.h
>> index c93dbad..f219b04 100644
>> --- a/include/acpi/actbl2.h
>> +++ b/include/acpi/actbl2.h
>> @@ -371,6 +371,7 @@ struct acpi_dbg2_device {
>> 
>> #define ACPI_DBG2_16550_COMPATIBLE  0x0000
>> #define ACPI_DBG2_16550_SUBSET      0x0001
>> +#define ACPI_DBG2_16550_32BIT       0x0002
>> #define ACPI_DBG2_ARM_PL011         0x0003
>> #define ACPI_DBG2_ARM_SBSA_32BIT    0x000D
>> #define ACPI_DBG2_ARM_SBSA_GENERIC  0x000E
>> --
> 
> This is an ACPICA change and it first needs to be made to the upstream
> ACPICA code base.
> 
> Thanks,
> Rafael