Re: [PATCH 1/2] ARM: Implemented support for VFP PM context saving

[Tony Lindgren <tony@atomide.com>]

* Tero Kristo <tero.kristo@nokia.com> [091119 07:12]:
> From: Tero Kristo <tero.kristo@nokia.com>
> 
> In some ARM architectures, like OMAP3, the VFP context can be lost during
> dynamic sleep cycle. For this purpose, there is now a function
> vfp_pm_save_context() that should be called before the VFP is assumed to
> lose context. Next VFP trap will then restore context automatically.
> 
> We need to have the last_VFP_context[cpu] cleared after the save in idle,
> else the restore would fail to restore when it sees that the last_VFP_context
> is same as the current threads vfp_state. This happens when the same
> process/thread traps an exception post idle.
> 
> Main work for this patch was done by Peter and Rajendra. Some cleanup and
> optimization by Tero.

This should go via the linux-arm-kernel@lists.infradead.org list.
We should probably merge them both via LAKML as they logically belong
toghether. Can you please resend, and also Cc linux-omap list?

For both, you can add Acked-by: Tony Lindgren <tony@atomide.com>
if you want to.

 
> Signed-off-by: Tero Kristo <tero.kristo@nokia.com>
> Cc: Vishwanath Sripathy <vishwanath.bs@ti.com>
> Cc: Rajendra Nayak <rnayak@ti.com>
> Cc: Richard Woodruff <r-woodruff2@ti.com>
> Cc: Peter 'p2' De Schrijver <peter.de-schrijver@nokia.com>
> ---
>  arch/arm/vfp/vfpmodule.c |   25 +++++++++++++++++++++++++
>  1 files changed, 25 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
> index 2d7423a..80a08bd 100644
> --- a/arch/arm/vfp/vfpmodule.c
> +++ b/arch/arm/vfp/vfpmodule.c
> @@ -329,6 +329,31 @@ static void vfp_enable(void *unused)
>  #ifdef CONFIG_PM
>  #include <linux/sysdev.h>
>  
> +void vfp_pm_save_context(void)
> +{
> +	struct thread_info *thread = current_thread_info();
> +	u32 fpexc = fmrx(FPEXC);
> +	__u32 cpu = thread->cpu;
> +
> +	if (last_VFP_context[cpu]) {
> +		if (!(fpexc & FPEXC_EN)) {
> +			/* enable vfp now to save context */
> +			vfp_enable(NULL);
> +			fmxr(FPEXC, fmrx(FPEXC) | FPEXC_EN);
> +		}
> +		vfp_save_state(last_VFP_context[cpu], fpexc);
> +
> +		/* Disable vfp. The next inst traps an exception and restores*/
> +		fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
> +
> +		/*
> +		 * This is needed else the restore might fail if it sees
> +		 * last_VFP_context if same as the current threads vfp_state.
> +		 */
> +		last_VFP_context[cpu] = NULL;
> +	}
> +}
> +
>  static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
>  {
>  	struct thread_info *ti = current_thread_info();
> -- 
> 1.5.4.3
> 
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