linux-kernel - Re: [PATCH V3 1/2] ACPI / EC: Fix broken big-endian 64bit platforms using 'global

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Date:	Wed, 16 Sep 2015 03:57:05 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>,
	Lv Zheng <lv.zheng@...el.com>
Cc:	gregkh@...uxfoundation.org, linaro-kernel@...ts.linaro.org,
	sboyd@...eaurora.org, arnd@...db.de, stable@...r.kernel.org,
	Len Brown <lenb@...nel.org>,
	"open list:ACPI" <linux-acpi@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 1/2] ACPI / EC: Fix broken big-endian 64bit platforms using 'global_lock'

On Tuesday, September 15, 2015 02:04:58 PM Viresh Kumar wrote:
> global_lock is defined as an unsigned long and accessing only its lower
> 32 bits from sysfs is incorrect, as we need to consider other 32 bits
> for big endian 64 bit systems.
> 
> Fix that by making global_lock an u32 instead.
> 
> Cc: <stable@...r.kernel.org>  # v4.1+
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> 
> ---
> Its marked just for # v4.1+, because arm64 has the first 64 big-endian
> platform with ACPI. And ACPI support for that is mainlined recently
> only (Arnd Bergmann).

OK

So are you aware of any ARM platform implementing the ACPI EC?

I am not.  Moreover, I'm not aware of any plans in that area.

> Another thing worth noticing is that, global_lock is getting an unsigned
> long long value assigned to it in ec_parse_device() and this is what
> Arnd had to say about that:
> 
> "I think that's fine, it does this because the _GLP variable in ACPI is
> defined as an u64. And that's what happens on 32-bit architectures
> anyway."
> 
> This patch should go via GregKH, as the second patch has dependency on
> it.
> 
> V2->V3:
> - Moved this out in a separate patch, so that it can be backported.

Lv, can you have a look at this, please?

> ---
>  drivers/acpi/ec_sys.c   | 2 +-
>  drivers/acpi/internal.h | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/ec_sys.c b/drivers/acpi/ec_sys.c
> index b4c216bab22b..bea8e425a8de 100644
> --- a/drivers/acpi/ec_sys.c
> +++ b/drivers/acpi/ec_sys.c
> @@ -128,7 +128,7 @@ static int acpi_ec_add_debugfs(struct acpi_ec *ec, unsigned int ec_device_count)
>  	if (!debugfs_create_x32("gpe", 0444, dev_dir, (u32 *)&first_ec->gpe))
>  		goto error;
>  	if (!debugfs_create_bool("use_global_lock", 0444, dev_dir,
> -				 (u32 *)&first_ec->global_lock))
> +				 &first_ec->global_lock))
>  		goto error;
>  
>  	if (write_support)
> diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
> index 9e426210c2a8..9db196de003c 100644
> --- a/drivers/acpi/internal.h
> +++ b/drivers/acpi/internal.h
> @@ -138,7 +138,7 @@ struct acpi_ec {
>  	unsigned long gpe;
>  	unsigned long command_addr;
>  	unsigned long data_addr;
> -	unsigned long global_lock;
> +	u32 global_lock;
>  	unsigned long flags;
>  	unsigned long reference_count;
>  	struct mutex mutex;
> 

Thanks,
Rafael

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