Re: [PATCH 1/7] ARM: zynqmp: set reset source

[Michael Tretter <m.tretter@pengutronix.de>]

On Thu, 24 Jun 2021 12:48:44 +0200, Ahmad Fatoum wrote:
> On 24.06.21 12:23, Michael Tretter wrote:
> > The reset reason is available in the APB register set on the ZynqMP.
> > Read the reset reason and set the reset source accordingly.
> > 
> > There might be multiple bits set in the APB register. Use the MSB for
> > determining the actual reset source.
> 
> APB is usually the AMBA Advanced Peripheral Bus. Perhaps CRL is the
> actual name of the register and APB just tells that it's mapped there?

Ack. The data sheet calls it "Clock and Reset control registers for LPD." I
will fix it in v2.

> 
> > 
> > Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
> > ---
> >  arch/arm/mach-zynqmp/Makefile              |  1 +
> >  arch/arm/mach-zynqmp/include/mach/zynqmp.h |  6 ++
> >  arch/arm/mach-zynqmp/zynqmp.c              | 74 ++++++++++++++++++++++
> >  3 files changed, 81 insertions(+)
> >  create mode 100644 arch/arm/mach-zynqmp/include/mach/zynqmp.h
> >  create mode 100644 arch/arm/mach-zynqmp/zynqmp.c
> > 
> > diff --git a/arch/arm/mach-zynqmp/Makefile b/arch/arm/mach-zynqmp/Makefile
> > index 021efc94afaf..14b8a4e46b87 100644
> > --- a/arch/arm/mach-zynqmp/Makefile
> > +++ b/arch/arm/mach-zynqmp/Makefile
> > @@ -1,2 +1,3 @@
> >  # SPDX-License-Identifier: GPL-2.0-or-later
> >  obj-y += firmware-zynqmp.o
> > +obj-y += zynqmp.o
> > diff --git a/arch/arm/mach-zynqmp/include/mach/zynqmp.h b/arch/arm/mach-zynqmp/include/mach/zynqmp.h
> > new file mode 100644
> > index 000000000000..f6c05f35a470
> > --- /dev/null
> > +++ b/arch/arm/mach-zynqmp/include/mach/zynqmp.h
> 
> Nitpick: revision.h sounds more self-describing.

Ok. I thought there might be some more soc specific function instead of
revision specific functions here, but revision.h is fine for me as well.

> 
> > @@ -0,0 +1,6 @@
> > +#ifndef __MACH_ZYNQMP_H
> > +#define __MACH_ZYNQMP_H
> > +
> > +int zynqmp_soc_revision(void);
> > +
> > +#endif /* __MACH_ZYNQMP_H */
> > diff --git a/arch/arm/mach-zynqmp/zynqmp.c b/arch/arm/mach-zynqmp/zynqmp.c
> > new file mode 100644
> > index 000000000000..2b3bd8406ce9
> > --- /dev/null
> > +++ b/arch/arm/mach-zynqmp/zynqmp.c
> > @@ -0,0 +1,74 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (C) 2020 Michael Tretter <m.tretter@pengutronix.de>
> > + */
> > +
> > +#include <common.h>
> > +#include <init.h>
> > +#include <linux/types.h>
> > +#include <reset_source.h>
> > +
> > +#include <mach/zynqmp.h>
> > +
> > +#define ZYNQMP_CRL_APB_BASE		0xff5e0000
> > +#define ZYNQMP_CRL_APB_RESET_REASON	(ZYNQMP_CRL_APB_BASE + 0x220)
> > +
> > +/* External POR: The PS_POR_B reset signal pin was asserted. */
> > +#define ZYNQMP_CRL_APB_RESET_REASON_EXTERNAL   BIT(0)
> > +/* Internal POR: A system error triggered a POR reset. */
> > +#define ZYNQMP_CRL_APB_RESET_REASON_INTERNAL   BIT(1)
> > +/* Internal system reset; A system error triggered a system reset. */
> > +#define ZYNQMP_CRL_APB_RESET_REASON_PMU        BIT(2)
> > +/* PS-only reset: Write to PMU_GLOBAL.GLOBAL_RESET [PS_ONLY_RST]. */
> > +#define ZYNQMP_CRL_APB_RESET_REASON_PSONLY     BIT(3)
> > +/* External system reset: The PS_SRST_B reset signal pin was asserted. */
> > +#define ZYNQMP_CRL_APB_RESET_REASON_SRST       BIT(4)
> > +/* Software system reset: Write to RESET_CTRL [soft_reset]. */
> > +#define ZYNQMP_CRL_APB_RESET_REASON_SOFT       BIT(5)
> > +/* Software debugger reset: Write to BLOCKONLY_RST [debug_only]. */
> > +#define ZYNQMP_CRL_APB_RESET_REASON_DEBUG_SYS  BIT(6)
> > +
> > +struct zynqmp_reset_reason {
> > +	u32 mask;
> > +	enum reset_src_type type;
> > +};
> > +
> > +static const struct zynqmp_reset_reason reset_reasons[] = {
> > +	{ ZYNQMP_CRL_APB_RESET_REASON_DEBUG_SYS,	RESET_UKWN },
> 
> RESET_JTAG?

I am not sure, if I understand RESET_JTAG correctly. The reference manual says
that it is like a soft reset while preserving the debug logic and originates
in the DAP controller. Is this RESET_JTAG?

> 
> > +	{ ZYNQMP_CRL_APB_RESET_REASON_SOFT,		RESET_RST },
> > +	{ ZYNQMP_CRL_APB_RESET_REASON_SRST,		RESET_POR },
> > +	{ ZYNQMP_CRL_APB_RESET_REASON_PSONLY,		RESET_POR },
> > +	{ ZYNQMP_CRL_APB_RESET_REASON_PMU,		RESET_POR },
> > +	{ ZYNQMP_CRL_APB_RESET_REASON_INTERNAL,		RESET_POR },
> > +	{ ZYNQMP_CRL_APB_RESET_REASON_EXTERNAL,		RESET_POR },
> 
> RESET_EXT?

This bit is set for a normal POR, too.

> 
> > +	{ /* sentinel */ }
> > +};
> > +
> > +static enum reset_src_type zynqmp_get_reset_src(void)
> > +{
> > +	enum reset_src_type type = RESET_UKWN;
> > +	unsigned int i;
> > +	u32 val;
> > +
> > +	val = readl(ZYNQMP_CRL_APB_RESET_REASON);
> > +
> > +	for (i = 0; i < ARRAY_SIZE(reset_reasons); i++) {
> > +		if (val & reset_reasons[i].mask) {
> > +			type = reset_reasons[i].type;
> > +			break;
> > +		}
> > +	}
> > +
> > +	pr_info("ZynqMP reset reason %s (ZYNQMP_CRL_APB_RESET_REASON: 0x%08x)\n",
> > +		reset_source_to_string(type), val);
> > +
> > +	return type;
> > +}
> > +
> > +static int zynqmp_init(void)
> > +{
> > +	reset_source_set(zynqmp_get_reset_src());
> > +
> > +	return 0;
> > +}
> > +postcore_initcall(zynqmp_init);
> > 

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