Re: [PATCH] ARM: mach-shmobile: Don't configure ARCH timer if PSCI is enabled

[Oleksandr]

On 18.04.19 10:14, Biju Das wrote:
> Hi Oleksandr,

Hi Biju

> Thanks for the patch.
>
> > Subject: [PATCH] ARM: mach-shmobile: Don't configure ARCH timer if PSCI is
> > enabled
> >
> > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> >
> > If CONFIG_PSCI is enabled then most likely we are running on PSCI-enabled
> > U-Boot which, we assume, has already taken care of configuring ARCH timer
> > stuff before switching to non-secure mode.
> >
> > Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> >
> > ---
> > A bit of context here...
> >
> > We are highly interested in Renesas "Stout" board support (r8a7790) in Xen
> > hypervisor. The reason is to have fully supported HW for performing
> > "OSSTEST" (Xen automatic test system) on ARM32.
> >
> > To reach that target we need a "generic way" for the secondary CPU cores
> > bring up and switching them to non-secure hyp mode.
> > So, the PSCI as a generic well-known way to bring up CPUs, was chosen for
> > that purpose.
> >
> > You can find corresponding patches for U-Boot here:
> > http://u-boot.10912.n7.nabble.com/PATCH-0-3-PSCI-support-for-r8a7790-
> > SoC-Lager-Stout-boards-td357352.html
> >
> > You can find corresponding patches for Xen hypervisor here:
> > https://www.mail-archive.com/xen-
> > devel@xxxxxxxxxxxxxxxxxxxx/msg43332.html
> >
> > To sumarize:
> > Together with enabling CONFIG_PSCI in shmobile_defconfig, current patch is
> > a minimal required change needed to run mainline Linux on top of PSCI-
> > enabled U-Boot.
> > There is no need to modify device tree. U-Boot will take care of inserting
> > proper "enable-method" strings in CPU nodes.
> >
> > ---
> >   arch/arm/mach-shmobile/setup-rcar-gen2.c | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm/mach-shmobile/setup-rcar-gen2.c b/arch/arm/mach-
> > shmobile/setup-rcar-gen2.c
> > index eea60b2..bac4490 100644
> > --- a/arch/arm/mach-shmobile/setup-rcar-gen2.c
> > +++ b/arch/arm/mach-shmobile/setup-rcar-gen2.c
> > @@ -32,7 +32,7 @@ static const struct of_device_id cpg_matches[]
> > __initconst = {
> >   	{ /* sentinel */ }
> >   };
> >
> > -static unsigned int __init get_extal_freq(void)
> > +static unsigned int __init __maybe_unused get_extal_freq(void)
> >   {
> >   	const struct of_device_id *match;
> >   	struct device_node *cpg, *extal;
> > @@ -60,6 +60,12 @@ static unsigned int __init get_extal_freq(void)
> >
> >   void __init rcar_gen2_timer_init(void)
> >   {
> > +/*
> > + * If CONFIG_PSCI is enabled then most likely we are running on
> > +PSCI-enabled
> > + * U-Boot which, we assume, has already taken care of configuring ARCH
> > +timer
> > + * stuff before switching to non-secure mode.
> > + */
> > +#if !defined(CONFIG_ARM_PSCI)
> Is it required?  If you see the below comment, it is already taken care
> by the below code.
>
> Is your code entering into this block, when booting  the kernel in NS mode?

No, the code below seems to do the proper things. If arch timer is 
configured in U-Boot (enabled and programmed with correct freq) then

that code doesn't try to update it.

But "#if !defined(CONFIG_ARM_PSCI)" wraps secure_cntvoff_init() call as 
well, which resets CNTVOFF,

and this is something I tried to avoid the first from being executed on 
a CPU, which is in SVC mode (when running on top of Xen).


I was thinking whether I should wrap arch timer updating procedure as 
well and decided to do so, but probably I shouldn't have.

> <snip>
>    /*
>   87          * Update the timer if it is either not running, or is not at the
>   88          * right frequency. The timer is only configurable in secure mode
>   89          * so this avoids an abort if the loader started the timer and
>   90          * entered the kernel in non-secure mode.
>   91          */
>   92
>   93         if ((ioread32(base + CNTCR) & 1) == 0 ||
>   94             ioread32(base + CNTFID0) != freq) {
>   95                 /* Update registers with correct frequency */
>   96                 iowrite32(freq, base + CNTFID0);
>   97                 asm volatile("mcr p15, 0, %0, c14, c0, 0" : : "r" (freq));
>   98
>   99                 /* make sure arch timer is started by setting bit 0 of CNTCR */
> 100                 iowrite32(1, base + CNTCR);
> 101         }
>
>
> Regards,
> Biju
>
> >   	void __iomem *base;
> >   	u32 freq;
> >
> > @@ -101,6 +107,7 @@ void __init rcar_gen2_timer_init(void)
> >   	}
> >
> >   	iounmap(base);
> > +#endif /* #if !defined(CONFIG_ARM_PSCI) */
> >
> >   	of_clk_init(NULL);
> >   	timer_probe();
> > --
> > 2.7.4

--
Regards,

Oleksandr Tyshchenko