linux-kernel - Re: [RFT][PATCH v1] ACPI: OSL: Use a threaded interrupt handler for SCI

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Date:   Tue, 28 Nov 2023 08:27:57 -0600
From:   Mario Limonciello <mario.limonciello@....com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Michal Wilczynski <michal.wilczynski@...el.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: Re: [RFT][PATCH v1] ACPI: OSL: Use a threaded interrupt handler for
 SCI

On 11/27/2023 13:57, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> In the current arrangement, all of the acpi_ev_sci_xrupt_handler() code
> is run as an interrupt handler for the SCI, in interrupt context.  Among
> other things, this causes it to run with local interrupts off which
> can be problematic if many GPEs are enabled and they are located in the
> I/O address space, for example (because in that case local interrupts
> will be off for the duration of all of the GPE hardware accesses carried
> out while handling an SCI combined and that may be quite a bit of time
> in extreme scenarios).
> 
> However, there is no particular reason why the code in question really
> needs to run in interrupt context and in particular, it has no specific
> reason to run with local interrupts off.  The only real requirement is
> to prevent multiple instences of it from running in parallel with each
> other, but that can be achieved regardless.
> 
> For this reason, use request_threaded_irq() instead of request_irq() for
> the ACPI SCI and pass IRQF_ONESHOT to it in flags to indicate that the
> interrupt needs to be masked while its handling thread is running so as
> to prevent it from re-triggering while it is being handled (and in
> particular until the final handled/not handled outcome is determined).
> 
> While at it, drop a redundant local variable from acpi_irq().
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> The code inspection and (necessarily limited) testing carried out by me
> are good indications that this should just always work, but there may
> be still some really odd platform configurations I'm overlooking, so if
> you have a way to give it a go, please do so.

Thanks for looping me in.

I tested it on a few different laptops I have on hand from different SoC 
generations and manufacturers and ensured that SCI was working correctly 
for usage and wakeup.  My base kernel was 6.7-rc3 plus some unrelated 
RTC timeout handling patches.

Tested-by: Mario Limonciello <mario.limonciello@....com>

> 
> ---
>   drivers/acpi/osl.c |    9 +++------
>   1 file changed, 3 insertions(+), 6 deletions(-)
> 
> Index: linux-pm/drivers/acpi/osl.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/osl.c
> +++ linux-pm/drivers/acpi/osl.c
> @@ -544,11 +544,7 @@ acpi_os_predefined_override(const struct
>   
>   static irqreturn_t acpi_irq(int irq, void *dev_id)
>   {
> -	u32 handled;
> -
> -	handled = (*acpi_irq_handler) (acpi_irq_context);
> -
> -	if (handled) {
> +	if ((*acpi_irq_handler)(acpi_irq_context)) {
>   		acpi_irq_handled++;
>   		return IRQ_HANDLED;
>   	} else {
> @@ -582,7 +578,8 @@ acpi_os_install_interrupt_handler(u32 gs
>   
>   	acpi_irq_handler = handler;
>   	acpi_irq_context = context;
> -	if (request_irq(irq, acpi_irq, IRQF_SHARED, "acpi", acpi_irq)) {
> +	if (request_threaded_irq(irq, NULL, acpi_irq, IRQF_SHARED | IRQF_ONESHOT,
> +			         "acpi", acpi_irq)) {
>   		pr_err("SCI (IRQ%d) allocation failed\n", irq);
>   		acpi_irq_handler = NULL;
>   		return AE_NOT_ACQUIRED;
> 
> 
>