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Date:   Fri, 20 Oct 2017 22:08:26 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Brendan Higgins <brendanhiggins@...gle.com>
Cc:     Avi Fishman <avifishman70@...il.com>, tmaimon77@...il.com,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Rick Altherr <raltherr@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>
Subject: Re: [PATCH v7 1/3] arm: npcm: add basic support for Nuvoton BMCs

On Fri, Oct 20, 2017 at 01:57:47PM -0700, Brendan Higgins wrote:
> On Fri, Oct 20, 2017 at 3:48 AM, Russell King - ARM Linux
> <linux@...linux.org.uk> wrote:
> > On Thu, Oct 19, 2017 at 03:50:48PM -0700, Brendan Higgins wrote:
> >> Adds basic support for the Nuvoton NPCM750 BMC.
> >>
> >> Signed-off-by: Brendan Higgins <brendanhiggins@...gle.com>
> >> Reviewed-by: Tomer Maimon <tmaimon77@...il.com>
> >> Reviewed-by: Avi Fishman <avifishman70@...il.com>
> >> Tested-by: Tomer Maimon <tmaimon77@...il.com>
> >> Tested-by: Avi Fishman <avifishman70@...il.com>
> >> ---
> >>  arch/arm/Kconfig             |  2 +
> >>  arch/arm/Makefile            |  1 +
> >>  arch/arm/mach-npcm/Kconfig   | 48 ++++++++++++++++++++++++
> >>  arch/arm/mach-npcm/Makefile  |  3 ++
> >>  arch/arm/mach-npcm/headsmp.S | 17 +++++++++
> >>  arch/arm/mach-npcm/npcm7xx.c | 34 +++++++++++++++++
> >>  arch/arm/mach-npcm/platsmp.c | 88 ++++++++++++++++++++++++++++++++++++++++++++
> >>  7 files changed, 193 insertions(+)
> >>  create mode 100644 arch/arm/mach-npcm/Kconfig
> >>  create mode 100644 arch/arm/mach-npcm/Makefile
> >>  create mode 100644 arch/arm/mach-npcm/headsmp.S
> >>  create mode 100644 arch/arm/mach-npcm/npcm7xx.c
> >>  create mode 100644 arch/arm/mach-npcm/platsmp.c
> >>
> >> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> >> index 61a0cb15067e..05543f1cfbde 100644
> >> --- a/arch/arm/Kconfig
> >> +++ b/arch/arm/Kconfig
> >> @@ -782,6 +782,8 @@ source "arch/arm/mach-netx/Kconfig"
> >>
> >>  source "arch/arm/mach-nomadik/Kconfig"
> >>
> >> +source "arch/arm/mach-npcm/Kconfig"
> >> +
> >>  source "arch/arm/mach-nspire/Kconfig"
> >>
> >>  source "arch/arm/plat-omap/Kconfig"
> >> diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> >> index 47d3a1ab08d2..60ca50c7d762 100644
> >> --- a/arch/arm/Makefile
> >> +++ b/arch/arm/Makefile
> >> @@ -191,6 +191,7 @@ machine-$(CONFIG_ARCH_MEDIATEK)           += mediatek
> >>  machine-$(CONFIG_ARCH_MXS)           += mxs
> >>  machine-$(CONFIG_ARCH_NETX)          += netx
> >>  machine-$(CONFIG_ARCH_NOMADIK)               += nomadik
> >> +machine-$(CONFIG_ARCH_NPCM)          += npcm
> >>  machine-$(CONFIG_ARCH_NSPIRE)                += nspire
> >>  machine-$(CONFIG_ARCH_OXNAS)         += oxnas
> >>  machine-$(CONFIG_ARCH_OMAP1)         += omap1
> >> diff --git a/arch/arm/mach-npcm/Kconfig b/arch/arm/mach-npcm/Kconfig
> >> new file mode 100644
> >> index 000000000000..21dfa8ce828f
> >> --- /dev/null
> >> +++ b/arch/arm/mach-npcm/Kconfig
> >> @@ -0,0 +1,48 @@
> >> +menuconfig ARCH_NPCM
> >> +     bool "Nuvoton NPCM Architecture"
> >> +     select ARCH_REQUIRE_GPIOLIB
> >> +     select USE_OF
> >> +     select PINCTRL
> >> +     select PINCTRL_NPCM7XX
> >> +
> >> +if ARCH_NPCM
> >> +
> >> +comment "NPCMX50 CPU type"
> >> +
> >> +config CPU_NPCM750
> >> +     depends on ARCH_NPCM && ARCH_MULTI_V7
> >> +     bool "Support for NPCM750 BMC CPU (Poleg)"
> >> +     select CACHE_L2X0
> >> +     select CPU_V7
> >> +     select ARM_GIC
> >> +     select HAVE_SMP
> >> +     select SMP
> >> +     select SMP_ON_UP
> >> +     select HAVE_ARM_SCU
> >> +     select HAVE_ARM_TWD if SMP
> >> +     select ARM_ERRATA_720789
> >> +     select ARM_ERRATA_754322
> >> +     select ARM_ERRATA_764369
> >> +     select ARM_ERRATA_794072
> >> +     select PL310_ERRATA_588369
> >> +     select PL310_ERRATA_727915
> >> +     select USB_EHCI_ROOT_HUB_TT
> >> +     select USB_ARCH_HAS_HCD
> >> +     select USB_ARCH_HAS_EHCI
> >> +     select USB_EHCI_HCD
> >> +     select USB_ARCH_HAS_OHCI
> >> +     select USB_OHCI_HCD
> >> +     select USB
> >> +     select FIQ
> >> +     select CPU_USE_DOMAINS
> >> +     select GENERIC_CLOCKEVENTS
> >> +     select CLKDEV_LOOKUP
> >> +     select COMMON_CLK if OF
> >> +     select NPCM750_TIMER
> >> +     select MFD_SYSCON
> >> +     help
> >> +       Support for NPCM750 BMC CPU (Poleg).
> >> +
> >> +       Nuvoton NPCM750 BMC based on the Cortex A9.
> >> +
> >> +endif
> >> diff --git a/arch/arm/mach-npcm/Makefile b/arch/arm/mach-npcm/Makefile
> >> new file mode 100644
> >> index 000000000000..78416055b854
> >> --- /dev/null
> >> +++ b/arch/arm/mach-npcm/Makefile
> >> @@ -0,0 +1,3 @@
> >> +AFLAGS_headsmp.o             += -march=armv7-a
> >> +
> >> +obj-$(CONFIG_CPU_NPCM750)    += npcm7xx.o platsmp.o headsmp.o
> >> diff --git a/arch/arm/mach-npcm/headsmp.S b/arch/arm/mach-npcm/headsmp.S
> >> new file mode 100644
> >> index 000000000000..9fccbbd49ed4
> >> --- /dev/null
> >> +++ b/arch/arm/mach-npcm/headsmp.S
> >> @@ -0,0 +1,17 @@
> >> +/*
> >> + * Copyright 2017 Google, Inc.
> >> + *
> >> + * This program is free software; you can redistribute it and/or modify
> >> + * it under the terms of the GNU General Public License version 2 as
> >> + * published by the Free Software Foundation.
> >> + */
> >> +
> >> +#include <linux/linkage.h>
> >> +#include <linux/init.h>
> >> +#include <asm/assembler.h>
> >> +
> >> +ENTRY(npcm7xx_secondary_startup)
> >> +     safe_svcmode_maskall r0
> >> +
> >> +     b       secondary_startup
> >> +ENDPROC(npcm7xx_secondary_startup)
> >
> > Why do you need this?  The switch to svc mode is already handled by
> > secondary_startup.
> 
> Florian Fainelli already brought this up:
> https://www.spinics.net/lists/arm-kernel/msg605126.html
> Without this the kernel complains that the core is started in
> "wrong/inconsistent mode":

The solution would be a comment to indicate why it's necessary :)

> 
> SMP: Total of 2 processors activated (398.13 BogoMIPS).
> CPU: WARNING: CPU(s) started in wrong/inconsistent modes (primary CPU
> mode 0x13)
> CPU: This may indicate a broken bootloader or firmware.
> 
> >
> >> diff --git a/arch/arm/mach-npcm/npcm7xx.c b/arch/arm/mach-npcm/npcm7xx.c
> >> new file mode 100644
> >> index 000000000000..132e9d587857
> >> --- /dev/null
> >> +++ b/arch/arm/mach-npcm/npcm7xx.c
> >> @@ -0,0 +1,34 @@
> >> +/*
> >> + * Copyright (c) 2017 Nuvoton Technology corporation.
> >> + * Copyright 2017 Google, Inc.
> >> + *
> >> + * This program is free software; you can redistribute it and/or modify
> >> + * it under the terms of the GNU General Public License version 2 as
> >> + * published by the Free Software Foundation.
> >> + */
> >> +
> >> +#include <linux/kernel.h>
> >> +#include <linux/types.h>
> >> +#include <asm/mach/arch.h>
> >> +#include <asm/mach-types.h>
> >> +#include <asm/mach/map.h>
> >> +#include <asm/hardware/cache-l2x0.h>
> >> +
> >> +#define NPCM7XX_AUX_VAL (L310_AUX_CTRL_INSTR_PREFETCH |                             \
> >> +                      L310_AUX_CTRL_DATA_PREFETCH |                         \
> >> +                      L310_AUX_CTRL_NS_LOCKDOWN |                           \
> >> +                      L310_AUX_CTRL_CACHE_REPLACE_RR |                      \
> >> +                      L2C_AUX_CTRL_SHARED_OVERRIDE |                        \
> >> +                      L310_AUX_CTRL_FULL_LINE_ZERO)
> >
> > Do you really need all these flags?
> 
> Tomer, Avi, do we need these? I got this from the original version of
> the driver.

The l2c driver manages L310_AUX_CTRL_FULL_LINE_ZERO itself, so you
shouldn't specify that.

L2C_AUX_CTRL_SHARED_OVERRIDE is managed via the "arm,shared-override"
DT property, so you should use that in DT instead.

Prefetching needs the prefetch control register configured to tune the
prefetching - that's platform specific so the l2c driver doesn't touch
it (it expects firmware to have configured it.)  If firmware needs to
configure that, it might as well configure the flags too as they're
shared into that very same register.  If not, I think the l2c prefetch
register defaults to a very small prefetch, and is probably not worth
setting the enable bits without configuring the depth of prefetch.

L310_AUX_CTRL_NS_LOCKDOWN is always enabled by the l2c driver, so
shouldn't be necessary.

So that leaves only L310_AUX_CTRL_CACHE_REPLACE_RR.

> 
> >
> >> +
> >> +static const char *const npcm7xx_dt_match[] = {
> >> +     "nuvoton,npcm750",
> >> +     NULL
> >> +};
> >> +
> >> +DT_MACHINE_START(NPCM7XX_DT, "NPCMX50 Chip family")
> >> +     .atag_offset    = 0x100,
> >> +     .dt_compat      = npcm7xx_dt_match,
> >> +     .l2c_aux_val    = NPCM7XX_AUX_VAL,
> >> +     .l2c_aux_mask   = ~NPCM7XX_AUX_VAL,
> >> +MACHINE_END
> >> diff --git a/arch/arm/mach-npcm/platsmp.c b/arch/arm/mach-npcm/platsmp.c
> >> new file mode 100644
> >> index 000000000000..450e83c3c531
> >> --- /dev/null
> >> +++ b/arch/arm/mach-npcm/platsmp.c
> >> @@ -0,0 +1,88 @@
> >> +/*
> >> + * Copyright 2017 Google, Inc.
> >> + *
> >> + * This program is free software; you can redistribute it and/or modify
> >> + * it under the terms of the GNU General Public License version 2 as
> >> + * published by the Free Software Foundation.
> >> + */
> >> +
> >> +#define pr_fmt(fmt) "PLATSMP: " fmt
> >
> > Maybe something more descriptive?
> >
> >> +
> >> +#include <linux/delay.h>
> >> +#include <linux/device.h>
> >> +#include <linux/smp.h>
> >> +#include <linux/io.h>
> >> +#include <linux/of.h>
> >> +#include <linux/of_device.h>
> >> +#include <linux/of_platform.h>
> >> +#include <linux/of_address.h>
> >> +#include <asm/cacheflush.h>
> >> +#include <asm/smp.h>
> >> +#include <asm/smp_plat.h>
> >> +#include <asm/smp_scu.h>
> >> +
> >> +#define NPCM7XX_SCRPAD_REG 0x13c
> >> +
> >> +extern void npcm7xx_secondary_startup(void);
> >> +
> >> +static int npcm7xx_smp_boot_secondary(unsigned int cpu,
> >> +                                   struct task_struct *idle)
> >> +{
> >> +     struct device_node *gcr_np;
> >> +     void __iomem *gcr_base;
> >> +     int ret = 0;
> >> +
> >> +     gcr_np = of_find_compatible_node(NULL, NULL, "nuvoton,npcm750-gcr");
> >> +     if (!gcr_np) {
> >> +             pr_err("no gcr device node\n");
> >> +             ret = -EFAULT;
> >
> > EFAULT is used for bad userspace addresses, it should not be used for
> > other stuff - and a missing node is certainly not a "Bad address".
> >
> >> +             goto out;
> >> +     }
> >> +     gcr_base = of_iomap(gcr_np, 0);
> >> +     if (!gcr_base) {
> >> +             pr_err("could not iomap gcr at: 0x%p\n", gcr_base);
> >> +             ret = -EFAULT;
> >
> > This is more -ENOMEM.
> >
> >> +             goto out;
> >> +     }
> >> +
> >> +     /* give boot ROM kernel start address. */
> >> +     iowrite32(__pa_symbol(npcm7xx_secondary_startup), gcr_base +
> >> +               NPCM7XX_SCRPAD_REG);
> >> +     /* make sure npcm7xx_secondary_startup is seen by all observers. */
> >> +     smp_wmb();
> >
> > I think you mean "make sure the previous write is seen by all observers".
> > However, doesn't "dsb_sev()" already do that?
> >
> >> +     dsb_sev();
> >> +     /* make sure write buffer is drained */
> >> +     mb();
> >
> > This looks over the top.
> >
> >> +
> >> +     iounmap(gcr_base);
> >> +out:
> >> +     return ret;
> >> +}
> >> +
> >> +static void __init npcm7xx_smp_prepare_cpus(unsigned int max_cpus)
> >> +{
> >> +     struct device_node *scu_np;
> >> +     void __iomem *scu_base;
> >> +
> >> +     scu_np = of_find_compatible_node(NULL, NULL, "arm,cortex-a9-scu");
> >> +     if (!scu_np) {
> >> +             pr_err("no scu device node\n");
> >> +             return;
> >> +     }
> >> +     scu_base = of_iomap(scu_np, 0);
> >> +     if (!scu_base) {
> >> +             pr_err("could not iomap scu at: 0x%p\n", scu_base);
> >> +             return;
> >> +     }
> >> +
> >> +     scu_enable(scu_base);
> >> +
> >> +     iounmap(scu_base);
> >> +}
> >> +
> >> +static struct smp_operations npcm7xx_smp_ops __initdata = {
> >> +     .smp_prepare_cpus = npcm7xx_smp_prepare_cpus,
> >> +     .smp_boot_secondary = npcm7xx_smp_boot_secondary,
> >> +};
> >> +
> >> +CPU_METHOD_OF_DECLARE(npcm7xx_smp, "nuvoton,npcm7xx-smp", &npcm7xx_smp_ops);
> >> --
> >> 2.15.0.rc0.271.g36b669edcc-goog
> >>
> >
> > --
> > RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> > FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
> > According to speedtest.net: 8.21Mbps down 510kbps up

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

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