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Message-ID: <529c73bb-849c-434f-888c-0b010d280424@alliedtelesis.co.nz>
Date: Sun, 30 Jun 2024 22:39:04 +0000
From: Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To: Rob Herring <robh@...nel.org>
CC: "tglx@...utronix.de" <tglx@...utronix.de>, "krzk+dt@...nel.org"
	<krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
	"tsbogend@...ha.franken.de" <tsbogend@...ha.franken.de>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	"paulburton@...nel.org" <paulburton@...nel.org>, "peterz@...radead.org"
	<peterz@...radead.org>, "mail@...ger-koblitz.de" <mail@...ger-koblitz.de>,
	"bert@...t.com" <bert@...t.com>, "john@...ozen.org" <john@...ozen.org>,
	"sander@...nheule.net" <sander@...nheule.net>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "linux-mips@...r.kernel.org"
	<linux-mips@...r.kernel.org>, "kabel@...nel.org" <kabel@...nel.org>,
	"ericwouds@...il.com" <ericwouds@...il.com>
Subject: Re: [PATCH v3 8/9] mips: generic: add fdt fixup for Realtek reference
 board


On 28/06/24 05:48, Rob Herring wrote:
> On Wed, Jun 26, 2024 at 10:33 PM Chris Packham
> <chris.packham@...iedtelesis.co.nz> wrote:
>> The bootloader used on the Realtek RTL9302C boards is an ancient vendor
>> fork of U-Boot that doesn't understand device trees. So to run a modern
>> kernel it is necessary use one of the APPENDED_DTB options.
>>
>> When appending the DTB the inintrd information, if present, needs to be
>> inserted into the /chosen device tree node. The bootloader provides the
>> initrd start/size via the firmware environment. Add a fdt fixup that
>> will update the device tree with the initrd information.
> Is this really specific to this board/soc?

Based on my sample size of 1 I can't say. I thought this was a quirk of 
the realtek SDK version of U-Boot because it's based on something old 
and dt unaware. I did think about putting this code in a more generic 
place but in the end I went with something less invasive figuring it 
could be expanded on later if needed.

> I think there are lots of MIPS boards in this state.

If anyone can confirm that I'd be happy to make the workaround kick in 
if the fw_env has an initrd_start in it. I'm not sure if there is any 
risk in that approach. I don't know how other mips boards are currently 
booting using the generic board support.

> The code to handle all the possible
> combinations of bootloader handoff information and sources of DTB is
> quite the mess. Just for DTB source you have bootloader DTB, appended
> DTB, or built-in DTB (and there's even logic if you have multiple of
> those). Contrast that to arm32 ('the zoo"), where you have 2 choices:
> bootloader DTB or appended DTB with legacy bootloader parameters
> transferred to DTB. All the uglyness is contained and the kernel boot
> deals with 1 possibility. </rant>
>
>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>> ---
>>
>> Notes:
>>      Changes in v3:
>>      - None
>>      Changes in v2:
>>      - update compatible string
>>
>>   arch/mips/generic/Makefile        |  1 +
>>   arch/mips/generic/board-realtek.c | 81 +++++++++++++++++++++++++++++++
>>   2 files changed, 82 insertions(+)
>>   create mode 100644 arch/mips/generic/board-realtek.c
>>
>> diff --git a/arch/mips/generic/Makefile b/arch/mips/generic/Makefile
>> index 56011d738441..ea0e4ad5e600 100644
>> --- a/arch/mips/generic/Makefile
>> +++ b/arch/mips/generic/Makefile
>> @@ -13,3 +13,4 @@ obj-$(CONFIG_LEGACY_BOARD_SEAD3)      += board-sead3.o
>>   obj-$(CONFIG_LEGACY_BOARD_OCELOT)      += board-ocelot.o
>>   obj-$(CONFIG_MACH_INGENIC)                     += board-ingenic.o
>>   obj-$(CONFIG_VIRT_BOARD_RANCHU)                += board-ranchu.o
>> +obj-$(CONFIG_MACH_REALTEK_RTL)         += board-realtek.o
>> diff --git a/arch/mips/generic/board-realtek.c b/arch/mips/generic/board-realtek.c
>> new file mode 100644
>> index 000000000000..cd83fbf1968c
>> --- /dev/null
>> +++ b/arch/mips/generic/board-realtek.c
>> @@ -0,0 +1,81 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
> Kernel license by default is GPL-2.0-only. Why do something different?

Copy and paste from the existing arch/mips/generic/board-*.c. I'm fine 
with making it GPL-2.0-only

>> +/*
>> + * Copyright (C) 2024 Allied Telesis
>> + */
>> +
>> +#include <linux/errno.h>
>> +#include <linux/libfdt.h>
>> +#include <linux/of_address.h>
> You aren't using this header.
Ack.
>> +#include <linux/types.h>
>> +
>> +#include <asm/fw/fw.h>
>> +#include <asm/machine.h>
>> +
>> +static __init int realtek_add_initrd(void *fdt)
>> +{
>> +       int node, err;
>> +       u32 start, size;
>> +
>> +       node = fdt_path_offset(fdt, "/chosen");
>> +       if (node < 0) {
>> +               pr_err("/chosen node not found\n");
>> +               return -ENOENT;
>> +       }
>> +
>> +       start = fw_getenvl("initrd_start");
>> +       size = fw_getenvl("initrd_size");
>> +
>> +       if (start == 0 && size == 0)
>> +               return 0;
>> +
>> +       pr_info("Adding initrd info from environment\n");
>> +
>> +       err = fdt_setprop_u32(fdt, node, "linux,initrd-start", start);
>> +       if (err) {
>> +               pr_err("unable to set initrd-start: %d\n", err);
>> +               return err;
>> +       }
>> +
>> +       err = fdt_setprop_u32(fdt, node, "linux,initrd-end", start + size);
>> +       if (err) {
>> +               pr_err("unable to set initrd-end: %d\n", err);
>> +               return err;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +static const struct mips_fdt_fixup realtek_fdt_fixups[] __initconst = {
>> +       { realtek_add_initrd, "add initrd" },
>> +       {},
>> +};
>> +
>> +static __init const void *realtek_fixup_fdt(const void *fdt, const void *match_data)
>> +{
>> +       static unsigned char fdt_buf[16 << 10] __initdata;
>> +       int err;
>> +
>> +       if (fdt_check_header(fdt))
>> +               panic("Corrupt DT");
>> +
>> +       fw_init_cmdline();
>> +
>> +       err = apply_mips_fdt_fixups(fdt_buf, sizeof(fdt_buf), fdt, realtek_fdt_fixups);
>> +       if (err)
>> +               panic("Unable to fixup FDT: %d", err);
>> +
>> +       return fdt_buf;
>> +
>> +}
>> +
>> +static const struct of_device_id realtek_of_match[] __initconst = {
>> +       {
>> +               .compatible = "realtek,rtl9302",
>> +       },
>> +       {}
>> +};
>> +
>> +MIPS_MACHINE(realtek) = {
>> +       .matches = realtek_of_match,
>> +       .fixup_fdt = realtek_fixup_fdt,
>> +};
>> --
>> 2.45.2
>>
>>

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