Re: [PATCH v3 3/3] ARM: at91: remove unnecessary of_platform_default_populate calls

[Alexander Dahl <ada@thorsis.com>]

Hello everyone,

I'm afraid this patch breaks finding rootfs on raw nand on sam9x60,
see below:

Am Mon, Jan 05, 2026 at 03:06:45PM -0600 schrieb Rob Herring (Arm):
> The DT core will call of_platform_default_populate, so it is not
> necessary for machine specific code to call it unless there are custom
> match entries, auxdata or parent device. Neither of those apply here, so
> remove the call.
> 
> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Tested-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

Not sure what was actually tested, but this change breaks booting from
raw NAND flash on our sam9x60 based board.  I bisected the boot
failure to this exact change.  Before the change I see the nand
controller messages in the kernel log like this:

    atmel-nand-controller 10000000.ebi:nand-controller: using dma0chan5 for DMA transfers
    nand: device found, Manufacturer ID: 0x01, Chip ID: 0xda
    nand: AMD/Spansion S34ML02G1
    nand: 256 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB size: 64

After the change, there are no kernel log messages related to nand at
all, the driver does not seem to load.  This of course leads to no mtd
and ubi devices created, no ubi volumes found, no rootfs, and
eventually this message:

    VFS: Cannot open root device "ubi0:rootfs2" or unknown-block(0,253): error -19

I tried to understand the whole patch series, and to my understanding
the intend was the device nodes still get populated, and the drivers
loaded, right?  Patch 1/3 is related to the atmel nand controller, and
that one is not in the tree yet when bisecting to the end.  However it
is present in v7.0-rc1 (and later) and trying to boot that kernel (or
7.0 or todays master) fails, too.  (Also I don't see those probe defer
messages related to SRAM on v7.0-rc1, so I assume that's not the
problem?)

Now the strange thing is: on a different hardware based on sama5d2
v7.0-rc1 boots fine from raw nand flash.  I wonder what's the
difference which makes it work on one atmel platform and not work on
the other?

I compared kernel .config of both boards, no obvious pieces missing.
Looking at the dts (and included dtsi) files of both boards I could
spot no mistake.  Also no obvious flaws in sama5d2.dtsi or
sam9x60.dtsi.

Note: raw NAND flash is the only storage for rootfs on our platforms,
we can not simply put rootfs to a different storage.  I could try
setting up NFS boot for further investigation, but that will take a
while.

Does anyone have an idea how to make booting from raw NAND flash work
on sam9x60 again (despite the obviously not desired revert)?  What can
I try?  What information would be interesting for debugging?

Greets
Alex

> ---
> v3:
>  - Fixup split between patch 2 and 3.
> 
> v2:
>  - Dust off and rebase to 6.18-rc1
>  - Add new platforms added since v1
> ---
>  arch/arm/mach-at91/at91rm9200.c |  9 ---------
>  arch/arm/mach-at91/at91sam9.c   |  9 ---------
>  arch/arm/mach-at91/sam9x60.c    |  9 ---------
>  arch/arm/mach-at91/sam9x7.c     |  9 ---------
>  arch/arm/mach-at91/sama5.c      | 16 ----------------
>  arch/arm/mach-at91/sama7.c      |  9 ---------
>  6 files changed, 61 deletions(-)
> 
> diff --git a/arch/arm/mach-at91/at91rm9200.c b/arch/arm/mach-at91/at91rm9200.c
> index 2ac564eb8bbb..d15997fff5d7 100644
> --- a/arch/arm/mach-at91/at91rm9200.c
> +++ b/arch/arm/mach-at91/at91rm9200.c
> @@ -7,18 +7,10 @@
>   *                2012 Joachim Eastwood <manabian@gmail.com>
>   */
>  
> -#include <linux/of.h>
> -#include <linux/of_platform.h>
> -
>  #include <asm/mach/arch.h>
>  
>  #include "generic.h"
>  
> -static void __init at91rm9200_dt_device_init(void)
> -{
> -	of_platform_default_populate(NULL, NULL, NULL);
> -}
> -
>  static const char *const at91rm9200_dt_board_compat[] __initconst = {
>  	"atmel,at91rm9200",
>  	NULL
> @@ -26,6 +18,5 @@ static const char *const at91rm9200_dt_board_compat[] __initconst = {
>  
>  DT_MACHINE_START(at91rm9200_dt, "Atmel AT91RM9200")
>  	.init_late	= at91rm9200_pm_init,
> -	.init_machine	= at91rm9200_dt_device_init,
>  	.dt_compat	= at91rm9200_dt_board_compat,
>  MACHINE_END
> diff --git a/arch/arm/mach-at91/at91sam9.c b/arch/arm/mach-at91/at91sam9.c
> index cf07cba4ee5d..b9d2909d1b65 100644
> --- a/arch/arm/mach-at91/at91sam9.c
> +++ b/arch/arm/mach-at91/at91sam9.c
> @@ -6,19 +6,11 @@
>   *                2011 Nicolas Ferre <nicolas.ferre@atmel.com>
>   */
>  
> -#include <linux/of.h>
> -#include <linux/of_platform.h>
> -
>  #include <asm/mach/arch.h>
>  #include <asm/system_misc.h>
>  
>  #include "generic.h"
>  
> -static void __init at91sam9_init(void)
> -{
> -	of_platform_default_populate(NULL, NULL, NULL);
> -}
> -
>  static const char *const at91_dt_board_compat[] __initconst = {
>  	"atmel,at91sam9",
>  	NULL
> @@ -27,6 +19,5 @@ static const char *const at91_dt_board_compat[] __initconst = {
>  DT_MACHINE_START(at91sam_dt, "Atmel AT91SAM9")
>  	/* Maintainer: Atmel */
>  	.init_late	= at91sam9_pm_init,
> -	.init_machine	= at91sam9_init,
>  	.dt_compat	= at91_dt_board_compat,
>  MACHINE_END
> diff --git a/arch/arm/mach-at91/sam9x60.c b/arch/arm/mach-at91/sam9x60.c
> index a31beaaeffcd..744bab2cbb92 100644
> --- a/arch/arm/mach-at91/sam9x60.c
> +++ b/arch/arm/mach-at91/sam9x60.c
> @@ -7,19 +7,11 @@
>   * Author: Claudiu Beznea <claudiu.beznea@microchip.com>
>   */
>  
> -#include <linux/of.h>
> -#include <linux/of_platform.h>
> -
>  #include <asm/mach/arch.h>
>  #include <asm/system_misc.h>
>  
>  #include "generic.h"
>  
> -static void __init sam9x60_init(void)
> -{
> -	of_platform_default_populate(NULL, NULL, NULL);
> -}
> -
>  static const char *const sam9x60_dt_board_compat[] __initconst = {
>  	"microchip,sam9x60",
>  	NULL
> @@ -28,6 +20,5 @@ static const char *const sam9x60_dt_board_compat[] __initconst = {
>  DT_MACHINE_START(sam9x60_dt, "Microchip SAM9X60")
>  	/* Maintainer: Microchip */
>  	.init_late	= sam9x60_pm_init,
> -	.init_machine	= sam9x60_init,
>  	.dt_compat	= sam9x60_dt_board_compat,
>  MACHINE_END
> diff --git a/arch/arm/mach-at91/sam9x7.c b/arch/arm/mach-at91/sam9x7.c
> index 0c73f7fefd4f..166c8625509d 100644
> --- a/arch/arm/mach-at91/sam9x7.c
> +++ b/arch/arm/mach-at91/sam9x7.c
> @@ -7,18 +7,10 @@
>   * Author: Varshini Rajendran <varshini.rajendran@microchip.com>
>   */
>  
> -#include <linux/of.h>
> -#include <linux/of_platform.h>
> -
>  #include <asm/mach/arch.h>
>  
>  #include "generic.h"
>  
> -static void __init sam9x7_init(void)
> -{
> -	of_platform_default_populate(NULL, NULL, NULL);
> -}
> -
>  static const char * const sam9x7_dt_board_compat[] __initconst = {
>  	"microchip,sam9x7",
>  	NULL
> @@ -27,6 +19,5 @@ static const char * const sam9x7_dt_board_compat[] __initconst = {
>  DT_MACHINE_START(sam9x7_dt, "Microchip SAM9X7")
>  	/* Maintainer: Microchip */
>  	.init_late	= sam9x7_pm_init,
> -	.init_machine	= sam9x7_init,
>  	.dt_compat	= sam9x7_dt_board_compat,
>  MACHINE_END
> diff --git a/arch/arm/mach-at91/sama5.c b/arch/arm/mach-at91/sama5.c
> index 576654cba82d..e56022f00800 100644
> --- a/arch/arm/mach-at91/sama5.c
> +++ b/arch/arm/mach-at91/sama5.c
> @@ -6,9 +6,6 @@
>   *                2013 Ludovic Desroches <ludovic.desroches@atmel.com>
>   */
>  
> -#include <linux/of.h>
> -#include <linux/of_platform.h>
> -
>  #include <asm/hardware/cache-l2x0.h>
>  #include <asm/mach/arch.h>
>  #include <asm/mach/map.h>
> @@ -30,11 +27,6 @@ static void __init sama5_secure_cache_init(void)
>  		outer_cache.write_sec = sama5_l2c310_write_sec;
>  }
>  
> -static void __init sama5_dt_device_init(void)
> -{
> -	of_platform_default_populate(NULL, NULL, NULL);
> -}
> -
>  static const char *const sama5_dt_board_compat[] __initconst = {
>  	"atmel,sama5",
>  	NULL
> @@ -43,7 +35,6 @@ static const char *const sama5_dt_board_compat[] __initconst = {
>  DT_MACHINE_START(sama5_dt, "Atmel SAMA5")
>  	/* Maintainer: Atmel */
>  	.init_late	= sama5_pm_init,
> -	.init_machine	= sama5_dt_device_init,
>  	.dt_compat	= sama5_dt_board_compat,
>  MACHINE_END
>  
> @@ -54,17 +45,11 @@ static const char *const sama5_alt_dt_board_compat[] __initconst = {
>  
>  DT_MACHINE_START(sama5_alt_dt, "Atmel SAMA5")
>  	/* Maintainer: Atmel */
> -	.init_machine	= sama5_dt_device_init,
>  	.init_late	= sama5_pm_init,
>  	.dt_compat	= sama5_alt_dt_board_compat,
>  	.l2c_aux_mask	= ~0UL,
>  MACHINE_END
>  
> -static void __init sama5d2_init(void)
> -{
> -	of_platform_default_populate(NULL, NULL, NULL);
> -}
> -
>  static const char *const sama5d2_compat[] __initconst = {
>  	"atmel,sama5d2",
>  	NULL
> @@ -72,7 +57,6 @@ static const char *const sama5d2_compat[] __initconst = {
>  
>  DT_MACHINE_START(sama5d2, "Atmel SAMA5")
>  	/* Maintainer: Atmel */
> -	.init_machine	= sama5d2_init,
>  	.init_early	= sama5_secure_cache_init,
>  	.init_late	= sama5d2_pm_init,
>  	.dt_compat	= sama5d2_compat,
> diff --git a/arch/arm/mach-at91/sama7.c b/arch/arm/mach-at91/sama7.c
> index 8bf57a020f1c..f56828d61199 100644
> --- a/arch/arm/mach-at91/sama7.c
> +++ b/arch/arm/mach-at91/sama7.c
> @@ -6,19 +6,11 @@
>   *
>   */
>  
> -#include <linux/of.h>
> -#include <linux/of_platform.h>
> -
>  #include <asm/mach/arch.h>
>  #include <asm/system_misc.h>
>  
>  #include "generic.h"
>  
> -static void __init sama7_dt_device_init(void)
> -{
> -	of_platform_default_populate(NULL, NULL, NULL);
> -}
> -
>  static const char *const sama7_dt_board_compat[] __initconst = {
>  	"microchip,sama7",
>  	NULL
> @@ -27,7 +19,6 @@ static const char *const sama7_dt_board_compat[] __initconst = {
>  DT_MACHINE_START(sama7_dt, "Microchip SAMA7")
>  	/* Maintainer: Microchip */
>  	.init_late	= sama7_pm_init,
> -	.init_machine	= sama7_dt_device_init,
>  	.dt_compat	= sama7_dt_board_compat,
>  MACHINE_END
>  
> 
> -- 
> 2.51.0
> 
> 

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