linux-kernel - RE: [RFC 3/3] arm: shmobile: Add the RZ/N1D SMP enabler driver.

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Date:   Tue, 17 Apr 2018 09:32:38 +0000
From:   Michel Pollet <michel.pollet@...renesas.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Simon Horman <horms@...ge.net.au>
CC:     Phil Edworthy <phil.edworthy@...esas.com>,
        "buserror+upstream@...il.com" <buserror+upstream@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Magnus Damm <magnus.damm@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Chen-Yu Tsai <wens@...e.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Andreas Färber <afaerber@...e.de>,
        Andy Gross <andy.gross@...aro.org>,
        Carlo Caione <carlo@...lessm.com>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Frank Rowand <frank.rowand@...y.com>,
        Juri Lelli <juri.lelli@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [RFC 3/3] arm: shmobile: Add the RZ/N1D SMP enabler driver.

Hi Florian,

On 16 April 2018 22:46, Florian Fainelli:
> Hi Michel,
>
> On 04/16/2018 02:34 AM, Michel Pollet wrote:
> > The Renesas RZ/N1D second CA7 is parked in a ROM pen at boot time, it
> > requires a special enable method to get it started at boot time.
> >
> > Signed-off-by: Michel Pollet <michel.pollet@...renesas.com>
>
> Some few comments below. This patch should probably be re-ordered in
> your patch series, I would expect you to have this become patch 2 and have
> patch 2 be patch 3 (first you add infrastructure for using something, then you
> make use of it).

Thanks, took that onboard for v2

>
> > +static int rzn1_smp_boot_secondary(unsigned int cpu, struct
> > +task_struct *idle) {
> > +if (!cpu_bootaddr)
> > +return -ENODEV;
> > +
> > +spin_lock(&cpu_lock);
> > +
> > +writel(virt_to_phys(secondary_startup), cpu_bootaddr);
>
> Consider using __pa_symbol() instead of virt_to_phys() since
> secondary_startup is part of the kernel's linear memory map.

Agreed.

>
> > +arch_send_wakeup_ipi_mask(cpumask_of(cpu));
> > +
> > +spin_unlock(&cpu_lock);
> > +
> > +return 0;
> > +}
> > +
> > +static void __init rzn1_smp_prepare_cpus(unsigned int max_cpus) {
> > +struct device_node *dn;
> > +int ret;
> > +u32 bootaddr;
> > +
> > +dn = of_get_cpu_node(1, NULL);
> > +if (!dn) {
> > +pr_err("CPU#1: missing device tree node\n");
> > +return;
> > +}
> > +/*
> > + * Determine the address from which the CPU is polling.
> > + */
> > +ret = of_property_read_u32(dn, "cpu-release-addr", &bootaddr);
> > +if (ret)
> > +pr_err("CPU#1: invalid cpu-release-addr property\n");
> > +
> > +of_node_put(dn);
> > +/* The bootloader *does* change this property */
>
> This comment should probably be moved above the function that fetches
> "cpu-release-addr"

Thanks, I've simplified that bit too..
>
> > +pr_info("CPU#1: cpu-release-addr %08x\n", (u32)bootaddr);
> > +
> > +if (!bootaddr)
> > +return;
>
> Would not you want to show a message here to help catch such conditions
>
> > +
> > +cpu_bootaddr = ioremap(bootaddr, sizeof(bootaddr));
>
> Relying on ioremap() to reject values that might be outside of the allowed
> range may be a little fragile, but I can't suggest any better alternative.

It's difficult, I'd have to add a memory map header I've been trying not to
use so far for KISS reason...

>
> > +if (!cpu_bootaddr)
> > +pr_err("CPU#1: cpu-release-addr map failed\n"); }
> > +
> > +static const struct smp_operations rzn1_smp_ops __initconst = {
> > +.smp_prepare_cpus = rzn1_smp_prepare_cpus,
> > +.smp_boot_secondary = rzn1_smp_boot_secondary, };
> > +CPU_METHOD_OF_DECLARE(rzn1_smp, "renesas,r9a06g032-smp",
> > +&rzn1_smp_ops);
> >
>

Michel




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