linux-kernel - Re: [PATCH v2 1/2] ACPI: SPCR: Use access width to determine mmio usage

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Date:   Mon, 3 Jul 2017 23:44:30 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Loc Ho <lho@....com>, Aleksey Makarov <aleksey.makarov@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Jon Mason <jon.mason@...adcom.com>,
        Jon Masters <jcm@...hat.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Robert Moore <robert.moore@...el.com>, Lv <lv.zheng@...el.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>,
        Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>,
        patches@....com
Subject: Re: [PATCH v2 1/2] ACPI: SPCR: Use access width to determine mmio usage

On Mon, Jul 3, 2017 at 11:33 PM, Loc Ho <lho@....com> wrote:
> The current SPCR code does not check the access width of the mmio, and
> uses a default of 8bit register accesses.  This prevents devices that
> only do 16 or 32bit register accesses from working.  By simply checking
> this field and setting the mmio string appropriately, this issue can be
> corrected.  To prevent any legacy issues, the code will default to 8bit
> accesses if the value is anything but 16 or 32.
>
> Signed-off-by: Loc Ho <lho@....com>
> [Re-send as single patch set]
> Signed-off-by: Jon Mason <jon.mason@...adcom.com>

Greg, Aleksey, any objections here?

If not, I'll route this through the ACPI tree.


> ---
>  drivers/acpi/spcr.c     | 18 ++++++++++++++++--
>  include/acpi/acrestyp.h |  7 +++++++
>  2 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
> index 3afa8c1..2905063 100644
> --- a/drivers/acpi/spcr.c
> +++ b/drivers/acpi/spcr.c
> @@ -74,8 +74,22 @@ int __init parse_spcr(bool earlycon)
>                 goto done;
>         }
>
> -       iotype = table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY ?
> -                       "mmio" : "io";
> +       if (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
> +               switch (table->serial_port.access_width) {
> +               default:
> +                       pr_err("Unexpected SPCR Access Width.  Defaulting to byte size\n");
> +               case ACPI_ACCESS_SIZE_BYTE:
> +                       iotype = "mmio";
> +                       break;
> +               case ACPI_ACCESS_SIZE_WORD:
> +                       iotype = "mmio16";
> +                       break;
> +               case ACPI_ACCESS_SIZE_DWORD:
> +                       iotype = "mmio32";
> +                       break;
> +               }
> +       } else
> +               iotype = "io";
>
>         switch (table->interface_type) {
>         case ACPI_DBG2_ARM_SBSA_32BIT:
> diff --git a/include/acpi/acrestyp.h b/include/acpi/acrestyp.h
> index f0f7403..781cb55 100644
> --- a/include/acpi/acrestyp.h
> +++ b/include/acpi/acrestyp.h
> @@ -372,6 +372,13 @@ struct acpi_resource_generic_register {
>         u64 address;
>  };
>
> +/* Generic Address Space Access Sizes */
> +#define ACPI_ACCESS_SIZE_UNDEFINED             0
> +#define ACPI_ACCESS_SIZE_BYTE                  1
> +#define ACPI_ACCESS_SIZE_WORD                  2
> +#define ACPI_ACCESS_SIZE_DWORD                 3
> +#define ACPI_ACCESS_SIZE_QWORD                 4
> +
>  struct acpi_resource_gpio {
>         u8 revision_id;
>         u8 connection_type;
> --
> 1.8.3.1
>