linux-kernel - Re: [PATCH 3/3] ACPI: create Lynxpoint clocks if LPSS devices are found during scan

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Message-ID: <2120845.xiQTdAgPNJ@vostro.rjw.lan>
Date:	Fri, 18 Jan 2013 00:07:16 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Len Brown <lenb@...nel.org>,
	Mike Turquette <mturquette@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH 3/3] ACPI: create Lynxpoint clocks if LPSS devices are found during scan

On Monday, January 14, 2013 04:46:28 PM Mika Westerberg wrote:
> Since we don't want to create the Lynxpoint LPSS clock tree on a machines
> where no LPSS exists at all we look for the Lynxpoint device ACPI HIDs
> during ACPI namespace scan and if a known device is seen we assume that it
> is safe to create the LPSS clocks.
> 
> Therefore we allow init function to be passed via acpi_platform_device_ids[]
> table which is called whenever the corresponding device is found.
> 
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> ---
>  drivers/acpi/scan.c |   36 +++++++++++++++++++++++++++---------
>  1 file changed, 27 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 6a12702..8d9965e 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -11,6 +11,7 @@
>  #include <linux/kthread.h>
>  #include <linux/dmi.h>
>  #include <linux/nls.h>
> +#include <linux/platform_device.h>
>  
>  #include <acpi/acpi_drivers.h>
>  
> @@ -29,6 +30,15 @@ extern struct acpi_device *acpi_root;
>  
>  static const char *dummy_hid = "device";
>  
> +static void lpt_lpss_init_once(void)
> +{
> +	static struct platform_device *pdev;
> +
> +	/* Lynxpoint LPSS clocks */
> +	if (!pdev)
> +		pdev = platform_device_register_simple("clk-lpt", -1, NULL, 0);
> +}
> +
>  /*
>   * The following ACPI IDs are known to be suitable for representing as
>   * platform devices.
> @@ -38,14 +48,14 @@ static const struct acpi_device_id acpi_platform_device_ids[] = {
>  	{ "PNP0D40" },
>  
>  	/* Haswell LPSS devices */
> -	{ "INT33C0", 0 },
> -	{ "INT33C1", 0 },
> -	{ "INT33C2", 0 },
> -	{ "INT33C3", 0 },
> -	{ "INT33C4", 0 },
> -	{ "INT33C5", 0 },
> -	{ "INT33C6", 0 },
> -	{ "INT33C7", 0 },
> +	{ "INT33C0", (kernel_ulong_t)lpt_lpss_init_once },
> +	{ "INT33C1", (kernel_ulong_t)lpt_lpss_init_once },
> +	{ "INT33C2", (kernel_ulong_t)lpt_lpss_init_once },
> +	{ "INT33C3", (kernel_ulong_t)lpt_lpss_init_once },
> +	{ "INT33C4", (kernel_ulong_t)lpt_lpss_init_once },
> +	{ "INT33C5", (kernel_ulong_t)lpt_lpss_init_once },
> +	{ "INT33C6", (kernel_ulong_t)lpt_lpss_init_once },
> +	{ "INT33C7", (kernel_ulong_t)lpt_lpss_init_once },
>  
>  	{ }
>  };
> @@ -1580,6 +1590,7 @@ static acpi_status acpi_bus_check_add(acpi_handle handle, u32 lvl_not_used,
>  static acpi_status acpi_bus_device_attach(acpi_handle handle, u32 lvl_not_used,
>  					  void *not_used, void **ret_not_used)
>  {
> +	const struct acpi_device_id *id;
>  	acpi_status status = AE_OK;
>  	struct acpi_device *device;
>  	unsigned long long sta_not_used;
> @@ -1595,7 +1606,14 @@ static acpi_status acpi_bus_device_attach(acpi_handle handle, u32 lvl_not_used,
>  	if (acpi_bus_get_device(handle, &device))
>  		return AE_CTRL_DEPTH;
>  
> -	if (!acpi_match_device_ids(device, acpi_platform_device_ids)) {
> +	id = __acpi_match_device(device, acpi_platform_device_ids);
> +	if (id) {
> +		void (*init)(void) = (void (*)(void))id->driver_data;
> +
> +		/* Run any initialization if required */
> +		if (init)
> +			init();
> +

I'd prefer this to be done by acpi_create_platform_device() and you can add
an extra arg to it for this purpose.

Moreover the driver_data need not be a function pointer.  I actually think it
should consist of a number of flags that may be set or unset and the 0 bit
could be ACPI_PLATFORM_CLK or something like this.  Then, if that is set in
its (new) second arg, acpi_create_platform_device() will do the
platform_device_register_simple("clk-lpt", ...), if not done already.

And yes, we may need those flags for other stuff.

>  		/* This is a known good platform device. */
>  		acpi_create_platform_device(device);
>  	} else if (device_attach(&device->dev) < 0) {
> 

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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