[PATCH 1/2] ARM: fix building NOMMU ARMv4/v5 kernels

[PATCH 1/2] ARM: fix building NOMMU ARMv4/v5 kernels

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

The removal of the old-style irq entry broke obscure NOMMU
configurations on machines that have an MMU:

ld.lld: error: undefined symbol: generic_handle_arch_irq
 referenced by kernel/entry-armv.o:(__irq_svc) in archive arch/arm/built-in.a

A follow-up patch to convert nvic to the generic_handle_arch_irq()
could have fixed this by removing the Kconfig conditional, but did
it differently.

Change the Kconfig logic so ARM machines now unconditionally
enable the feature.

I have also submitted a patch to remove support for the configurations
that broke, but fixing the regression first is a trivial and correct
change.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 54f481a2308e ("ARM: remove old-style irq entry")
Fixes: 52d240871760 ("irqchip: nvic: Use GENERIC_IRQ_MULTI_HANDLER")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
This patch should go into the arm/devel-stable branch that has
the arm-irq-and-vmap-stacks-for-rmk patches from Ard
---
 arch/arm/Kconfig        | 2 +-
 drivers/irqchip/Kconfig | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index e9975ddd5034..5f0b40bab4fb 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -60,7 +60,7 @@ config ARM
 	select GENERIC_CPU_AUTOPROBE
 	select GENERIC_EARLY_IOREMAP
 	select GENERIC_IDLE_POLL_SETUP
-	select GENERIC_IRQ_MULTI_HANDLER if MMU
+	select GENERIC_IRQ_MULTI_HANDLER
 	select GENERIC_IRQ_PROBE
 	select GENERIC_IRQ_SHOW
 	select GENERIC_IRQ_SHOW_LEVEL
diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index 488eaa14d3a7..7038957f4a77 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -58,7 +58,6 @@ config ARM_NVIC
 	bool
 	select IRQ_DOMAIN_HIERARCHY
 	select GENERIC_IRQ_CHIP
-	select GENERIC_IRQ_MULTI_HANDLER
 
 config ARM_VIC
 	bool
-- 
2.29.2

[PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

It is possible to build MMU-less kernels for Cortex-M base
microcrontrollers as well as a couple of older platforms that
have not been converted to CONFIG_ARCH_MULTIPLATFORM,
specifically ep93xx, footbridge, dove, sa1100 and s3c24xx.

It seems unlikely that anybody has tested those configurations
in recent years, as even building them is frequently broken.
A patch I submitted caused another build time regression
in this configuration. I sent a patch for that, but it seems
better to also remove the option entirely, leaving ARMv7-M
as the only supported Arm NOMMU target for simplicity.

This addresses several build failures in randconfig builds that
have accumulated over the years.

Cc: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
If there are no objections, I'd apply this patch to the soc
tree for 5.18 as a cleanup.
---
 arch/arm/Kconfig                              | 34 +++++++------------
 .../mach-footbridge/include/mach/hardware.h   | 20 ++++-------
 arch/arm/mach-footbridge/include/mach/io.h    | 20 -----------
 arch/arm/mach-integrator/hardware.h           |  5 ---
 4 files changed, 20 insertions(+), 59 deletions(-)
 delete mode 100644 arch/arm/mach-footbridge/include/mach/io.h

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 5f0b40bab4fb..d184377ce2ae 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -304,6 +304,17 @@ config MMU
 	  Select if you want MMU-based virtualised addressing space
 	  support by paged memory management. If unsure, say 'Y'.
 
+config ARM_SINGLE_ARMV7M
+	def_bool !MMU
+	select ARM_NVIC
+	select AUTO_ZRELADDR
+	select TIMER_OF
+	select COMMON_CLK
+	select CPU_V7M
+	select NO_IOPORT_MAP
+	select SPARSE_IRQ
+	select USE_OF
+
 config ARCH_MMAP_RND_BITS_MIN
 	default 8
 
@@ -318,12 +329,11 @@ config ARCH_MMAP_RND_BITS_MAX
 #
 choice
 	prompt "ARM system type"
-	default ARM_SINGLE_ARMV7M if !MMU
-	default ARCH_MULTIPLATFORM if MMU
+	depends on MMU
+	default ARCH_MULTIPLATFORM
 
 config ARCH_MULTIPLATFORM
 	bool "Allow multiple platforms to be selected"
-	depends on MMU
 	select ARCH_FLATMEM_ENABLE
 	select ARCH_SPARSEMEM_ENABLE
 	select ARCH_SELECT_MEMORY_MODEL
@@ -337,18 +347,6 @@ config ARCH_MULTIPLATFORM
 	select SPARSE_IRQ
 	select USE_OF
 
-config ARM_SINGLE_ARMV7M
-	bool "ARMv7-M based platforms (Cortex-M0/M3/M4)"
-	depends on !MMU
-	select ARM_NVIC
-	select AUTO_ZRELADDR
-	select TIMER_OF
-	select COMMON_CLK
-	select CPU_V7M
-	select NO_IOPORT_MAP
-	select SPARSE_IRQ
-	select USE_OF
-
 config ARCH_EP93XX
 	bool "EP93xx-based"
 	select ARCH_SPARSEMEM_ENABLE
@@ -367,7 +365,6 @@ config ARCH_FOOTBRIDGE
 	bool "FootBridge"
 	select CPU_SA110
 	select FOOTBRIDGE
-	select NEED_MACH_IO_H if !MMU
 	select NEED_MACH_MEMORY_H
 	help
 	  Support for systems based on the DC21285 companion chip
@@ -375,7 +372,6 @@ config ARCH_FOOTBRIDGE
 
 config ARCH_IOP32X
 	bool "IOP32x-based"
-	depends on MMU
 	select CPU_XSCALE
 	select GPIO_IOP
 	select GPIOLIB
@@ -387,7 +383,6 @@ config ARCH_IOP32X
 
 config ARCH_IXP4XX
 	bool "IXP4xx-based"
-	depends on MMU
 	select ARCH_SUPPORTS_BIG_ENDIAN
 	select ARM_PATCH_PHYS_VIRT
 	select CPU_XSCALE
@@ -418,7 +413,6 @@ config ARCH_DOVE
 
 config ARCH_PXA
 	bool "PXA2xx/PXA3xx-based"
-	depends on MMU
 	select ARCH_MTD_XIP
 	select ARM_CPU_SUSPEND if PM
 	select AUTO_ZRELADDR
@@ -437,7 +431,6 @@ config ARCH_PXA
 
 config ARCH_RPC
 	bool "RiscPC"
-	depends on MMU
 	depends on !CC_IS_CLANG && GCC_VERSION < 90100 && GCC_VERSION >= 60000
 	select ARCH_ACORN
 	select ARCH_MAY_HAVE_PC_FDC
@@ -493,7 +486,6 @@ config ARCH_S3C24XX
 
 config ARCH_OMAP1
 	bool "TI OMAP1"
-	depends on MMU
 	select ARCH_OMAP
 	select CLKSRC_MMIO
 	select GENERIC_IRQ_CHIP
diff --git a/arch/arm/mach-footbridge/include/mach/hardware.h b/arch/arm/mach-footbridge/include/mach/hardware.h
index ecaf6e7388d9..985ad3a95671 100644
--- a/arch/arm/mach-footbridge/include/mach/hardware.h
+++ b/arch/arm/mach-footbridge/include/mach/hardware.h
@@ -21,32 +21,26 @@
  * 0xf0000000	0x80000000	16MB	ISA memory
  */
 
-#ifdef CONFIG_MMU
-#define MMU_IO(a, b)	(a)
-#else
-#define MMU_IO(a, b)	(b)
-#endif
-
 #define XBUS_SIZE		0x00100000
-#define XBUS_BASE		MMU_IO(0xff800000, 0x40000000)
+#define XBUS_BASE		0xff800000
 
 #define ARMCSR_SIZE		0x00100000
-#define ARMCSR_BASE		MMU_IO(0xfe000000, 0x42000000)
+#define ARMCSR_BASE		0xfe000000
 
 #define WFLUSH_SIZE		0x00100000
-#define WFLUSH_BASE		MMU_IO(0xfd000000, 0x78000000)
+#define WFLUSH_BASE		0xfd000000
 
 #define PCIIACK_SIZE		0x00100000
-#define PCIIACK_BASE		MMU_IO(0xfc000000, 0x79000000)
+#define PCIIACK_BASE		0xfc000000
 
 #define PCICFG1_SIZE		0x01000000
-#define PCICFG1_BASE		MMU_IO(0xfb000000, 0x7a000000)
+#define PCICFG1_BASE		0xfb000000
 
 #define PCICFG0_SIZE		0x01000000
-#define PCICFG0_BASE		MMU_IO(0xfa000000, 0x7b000000)
+#define PCICFG0_BASE		0xfa000000
 
 #define PCIMEM_SIZE		0x01000000
-#define PCIMEM_BASE		MMU_IO(0xf0000000, 0x80000000)
+#define PCIMEM_BASE		0xf0000000
 
 #define XBUS_CS2		0x40012000
 
diff --git a/arch/arm/mach-footbridge/include/mach/io.h b/arch/arm/mach-footbridge/include/mach/io.h
deleted file mode 100644
index 4e18b921373f..000000000000
--- a/arch/arm/mach-footbridge/include/mach/io.h
+++ /dev/null
@@ -1,20 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- *  arch/arm/mach-footbridge/include/mach/io.h
- *
- *  Copyright (C) 1997-1999 Russell King
- *
- *  Modifications:
- *   06-12-1997	RMK	Created.
- *   07-04-1999	RMK	Major cleanup
- */
-#ifndef __ASM_ARM_ARCH_IO_H
-#define __ASM_ARM_ARCH_IO_H
-
-/*
- * Translation of various i/o addresses to host addresses for !CONFIG_MMU
- */
-#define PCIO_BASE       0x7c000000
-#define __io(a)			((void __iomem *)(PCIO_BASE + (a)))
-
-#endif
diff --git a/arch/arm/mach-integrator/hardware.h b/arch/arm/mach-integrator/hardware.h
index 4d6ade3dd4ee..81ce09e3ad45 100644
--- a/arch/arm/mach-integrator/hardware.h
+++ b/arch/arm/mach-integrator/hardware.h
@@ -16,12 +16,7 @@
 #define IO_START		INTEGRATOR_HDR_BASE        // PA of IO
 
 /* macro to get at IO space when running virtually */
-#ifdef CONFIG_MMU
 #define IO_ADDRESS(x)	(((x) & 0x000fffff) | (((x) >> 4) & 0x0ff00000) | IO_BASE)
-#else
-#define IO_ADDRESS(x)	(x)
-#endif
-
 #define __io_address(n)		((void __iomem *)IO_ADDRESS(n))
 
 /*
-- 
2.29.2

Re: [PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Robin Murphy]

On 2022-03-09 14:40, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> It is possible to build MMU-less kernels for Cortex-M base
> microcrontrollers as well as a couple of older platforms that
> have not been converted to CONFIG_ARCH_MULTIPLATFORM,
> specifically ep93xx, footbridge, dove, sa1100 and s3c24xx.
> 
> It seems unlikely that anybody has tested those configurations
> in recent years, as even building them is frequently broken.
> A patch I submitted caused another build time regression
> in this configuration. I sent a patch for that, but it seems
> better to also remove the option entirely, leaving ARMv7-M
> as the only supported Arm NOMMU target for simplicity.

In that case, it would probably make sense to garbage-collect all the 
configs, setup code and other stuff relating to older MMU-less CPU cores 
like ARM1156, ARM940, etc. at the same time.

Robin.

> This addresses several build failures in randconfig builds that
> have accumulated over the years.
> 
> Cc: Vladimir Murzin <vladimir.murzin@arm.com>
> Cc: Russell King <linux@armlinux.org.uk>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> If there are no objections, I'd apply this patch to the soc
> tree for 5.18 as a cleanup.
> ---
>   arch/arm/Kconfig                              | 34 +++++++------------
>   .../mach-footbridge/include/mach/hardware.h   | 20 ++++-------
>   arch/arm/mach-footbridge/include/mach/io.h    | 20 -----------
>   arch/arm/mach-integrator/hardware.h           |  5 ---
>   4 files changed, 20 insertions(+), 59 deletions(-)
>   delete mode 100644 arch/arm/mach-footbridge/include/mach/io.h
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 5f0b40bab4fb..d184377ce2ae 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -304,6 +304,17 @@ config MMU
>   	  Select if you want MMU-based virtualised addressing space
>   	  support by paged memory management. If unsure, say 'Y'.
>   
> +config ARM_SINGLE_ARMV7M
> +	def_bool !MMU
> +	select ARM_NVIC
> +	select AUTO_ZRELADDR
> +	select TIMER_OF
> +	select COMMON_CLK
> +	select CPU_V7M
> +	select NO_IOPORT_MAP
> +	select SPARSE_IRQ
> +	select USE_OF
> +
>   config ARCH_MMAP_RND_BITS_MIN
>   	default 8
>   
> @@ -318,12 +329,11 @@ config ARCH_MMAP_RND_BITS_MAX
>   #
>   choice
>   	prompt "ARM system type"
> -	default ARM_SINGLE_ARMV7M if !MMU
> -	default ARCH_MULTIPLATFORM if MMU
> +	depends on MMU
> +	default ARCH_MULTIPLATFORM
>   
>   config ARCH_MULTIPLATFORM
>   	bool "Allow multiple platforms to be selected"
> -	depends on MMU
>   	select ARCH_FLATMEM_ENABLE
>   	select ARCH_SPARSEMEM_ENABLE
>   	select ARCH_SELECT_MEMORY_MODEL
> @@ -337,18 +347,6 @@ config ARCH_MULTIPLATFORM
>   	select SPARSE_IRQ
>   	select USE_OF
>   
> -config ARM_SINGLE_ARMV7M
> -	bool "ARMv7-M based platforms (Cortex-M0/M3/M4)"
> -	depends on !MMU
> -	select ARM_NVIC
> -	select AUTO_ZRELADDR
> -	select TIMER_OF
> -	select COMMON_CLK
> -	select CPU_V7M
> -	select NO_IOPORT_MAP
> -	select SPARSE_IRQ
> -	select USE_OF
> -
>   config ARCH_EP93XX
>   	bool "EP93xx-based"
>   	select ARCH_SPARSEMEM_ENABLE
> @@ -367,7 +365,6 @@ config ARCH_FOOTBRIDGE
>   	bool "FootBridge"
>   	select CPU_SA110
>   	select FOOTBRIDGE
> -	select NEED_MACH_IO_H if !MMU
>   	select NEED_MACH_MEMORY_H
>   	help
>   	  Support for systems based on the DC21285 companion chip
> @@ -375,7 +372,6 @@ config ARCH_FOOTBRIDGE
>   
>   config ARCH_IOP32X
>   	bool "IOP32x-based"
> -	depends on MMU
>   	select CPU_XSCALE
>   	select GPIO_IOP
>   	select GPIOLIB
> @@ -387,7 +383,6 @@ config ARCH_IOP32X
>   
>   config ARCH_IXP4XX
>   	bool "IXP4xx-based"
> -	depends on MMU
>   	select ARCH_SUPPORTS_BIG_ENDIAN
>   	select ARM_PATCH_PHYS_VIRT
>   	select CPU_XSCALE
> @@ -418,7 +413,6 @@ config ARCH_DOVE
>   
>   config ARCH_PXA
>   	bool "PXA2xx/PXA3xx-based"
> -	depends on MMU
>   	select ARCH_MTD_XIP
>   	select ARM_CPU_SUSPEND if PM
>   	select AUTO_ZRELADDR
> @@ -437,7 +431,6 @@ config ARCH_PXA
>   
>   config ARCH_RPC
>   	bool "RiscPC"
> -	depends on MMU
>   	depends on !CC_IS_CLANG && GCC_VERSION < 90100 && GCC_VERSION >= 60000
>   	select ARCH_ACORN
>   	select ARCH_MAY_HAVE_PC_FDC
> @@ -493,7 +486,6 @@ config ARCH_S3C24XX
>   
>   config ARCH_OMAP1
>   	bool "TI OMAP1"
> -	depends on MMU
>   	select ARCH_OMAP
>   	select CLKSRC_MMIO
>   	select GENERIC_IRQ_CHIP
> diff --git a/arch/arm/mach-footbridge/include/mach/hardware.h b/arch/arm/mach-footbridge/include/mach/hardware.h
> index ecaf6e7388d9..985ad3a95671 100644
> --- a/arch/arm/mach-footbridge/include/mach/hardware.h
> +++ b/arch/arm/mach-footbridge/include/mach/hardware.h
> @@ -21,32 +21,26 @@
>    * 0xf0000000	0x80000000	16MB	ISA memory
>    */
>   
> -#ifdef CONFIG_MMU
> -#define MMU_IO(a, b)	(a)
> -#else
> -#define MMU_IO(a, b)	(b)
> -#endif
> -
>   #define XBUS_SIZE		0x00100000
> -#define XBUS_BASE		MMU_IO(0xff800000, 0x40000000)
> +#define XBUS_BASE		0xff800000
>   
>   #define ARMCSR_SIZE		0x00100000
> -#define ARMCSR_BASE		MMU_IO(0xfe000000, 0x42000000)
> +#define ARMCSR_BASE		0xfe000000
>   
>   #define WFLUSH_SIZE		0x00100000
> -#define WFLUSH_BASE		MMU_IO(0xfd000000, 0x78000000)
> +#define WFLUSH_BASE		0xfd000000
>   
>   #define PCIIACK_SIZE		0x00100000
> -#define PCIIACK_BASE		MMU_IO(0xfc000000, 0x79000000)
> +#define PCIIACK_BASE		0xfc000000
>   
>   #define PCICFG1_SIZE		0x01000000
> -#define PCICFG1_BASE		MMU_IO(0xfb000000, 0x7a000000)
> +#define PCICFG1_BASE		0xfb000000
>   
>   #define PCICFG0_SIZE		0x01000000
> -#define PCICFG0_BASE		MMU_IO(0xfa000000, 0x7b000000)
> +#define PCICFG0_BASE		0xfa000000
>   
>   #define PCIMEM_SIZE		0x01000000
> -#define PCIMEM_BASE		MMU_IO(0xf0000000, 0x80000000)
> +#define PCIMEM_BASE		0xf0000000
>   
>   #define XBUS_CS2		0x40012000
>   
> diff --git a/arch/arm/mach-footbridge/include/mach/io.h b/arch/arm/mach-footbridge/include/mach/io.h
> deleted file mode 100644
> index 4e18b921373f..000000000000
> --- a/arch/arm/mach-footbridge/include/mach/io.h
> +++ /dev/null
> @@ -1,20 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0-only */
> -/*
> - *  arch/arm/mach-footbridge/include/mach/io.h
> - *
> - *  Copyright (C) 1997-1999 Russell King
> - *
> - *  Modifications:
> - *   06-12-1997	RMK	Created.
> - *   07-04-1999	RMK	Major cleanup
> - */
> -#ifndef __ASM_ARM_ARCH_IO_H
> -#define __ASM_ARM_ARCH_IO_H
> -
> -/*
> - * Translation of various i/o addresses to host addresses for !CONFIG_MMU
> - */
> -#define PCIO_BASE       0x7c000000
> -#define __io(a)			((void __iomem *)(PCIO_BASE + (a)))
> -
> -#endif
> diff --git a/arch/arm/mach-integrator/hardware.h b/arch/arm/mach-integrator/hardware.h
> index 4d6ade3dd4ee..81ce09e3ad45 100644
> --- a/arch/arm/mach-integrator/hardware.h
> +++ b/arch/arm/mach-integrator/hardware.h
> @@ -16,12 +16,7 @@
>   #define IO_START		INTEGRATOR_HDR_BASE        // PA of IO
>   
>   /* macro to get at IO space when running virtually */
> -#ifdef CONFIG_MMU
>   #define IO_ADDRESS(x)	(((x) & 0x000fffff) | (((x) >> 4) & 0x0ff00000) | IO_BASE)
> -#else
> -#define IO_ADDRESS(x)	(x)
> -#endif
> -
>   #define __io_address(n)		((void __iomem *)IO_ADDRESS(n))
>   
>   /*

Re: [PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Arnd Bergmann]

On Wed, Mar 9, 2022 at 4:48 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 2022-03-09 14:40, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > It is possible to build MMU-less kernels for Cortex-M base
> > microcrontrollers as well as a couple of older platforms that
> > have not been converted to CONFIG_ARCH_MULTIPLATFORM,
> > specifically ep93xx, footbridge, dove, sa1100 and s3c24xx.
> >
> > It seems unlikely that anybody has tested those configurations
> > in recent years, as even building them is frequently broken.
> > A patch I submitted caused another build time regression
> > in this configuration. I sent a patch for that, but it seems
> > better to also remove the option entirely, leaving ARMv7-M
> > as the only supported Arm NOMMU target for simplicity.
>
> In that case, it would probably make sense to garbage-collect all the
> configs, setup code and other stuff relating to older MMU-less CPU cores
> like ARM1156, ARM940, etc. at the same time.

Right, good idea. These are only selected by CONFIG_ARCH_INTEGRATOR,
but that in turn doesn't build for CONFIG_MMU=n because it depends on
ARCH_MULTIPLATFORM. I'll send a patch for these.

I also went back and forth between removing the #ifdefs in
arch/arm/mm/proc-*.S for this patch, though I did not do that in the end.
We may still want them at least for proc-v7.S because that is a small
chance that someone will want to support Cortex-R.

        Arnd

Re: [PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Vladimir Murzin]

On 3/9/22 4:17 PM, Arnd Bergmann wrote:
> On Wed, Mar 9, 2022 at 4:48 PM Robin Murphy <robin.murphy@arm.com> wrote:
>>
>> On 2022-03-09 14:40, Arnd Bergmann wrote:
>>> From: Arnd Bergmann <arnd@arndb.de>
>>>
>>> It is possible to build MMU-less kernels for Cortex-M base
>>> microcrontrollers as well as a couple of older platforms that
>>> have not been converted to CONFIG_ARCH_MULTIPLATFORM,
>>> specifically ep93xx, footbridge, dove, sa1100 and s3c24xx.
>>>
>>> It seems unlikely that anybody has tested those configurations
>>> in recent years, as even building them is frequently broken.
>>> A patch I submitted caused another build time regression
>>> in this configuration. I sent a patch for that, but it seems
>>> better to also remove the option entirely, leaving ARMv7-M
>>> as the only supported Arm NOMMU target for simplicity.
>>
>> In that case, it would probably make sense to garbage-collect all the
>> configs, setup code and other stuff relating to older MMU-less CPU cores
>> like ARM1156, ARM940, etc. at the same time.
> 
> Right, good idea. These are only selected by CONFIG_ARCH_INTEGRATOR,
> but that in turn doesn't build for CONFIG_MMU=n because it depends on
> ARCH_MULTIPLATFORM. I'll send a patch for these.
> 
> I also went back and forth between removing the #ifdefs in
> arch/arm/mm/proc-*.S for this patch, though I did not do that in the end.
> We may still want them at least for proc-v7.S because that is a small
> chance that someone will want to support Cortex-R.
> 

I'd appreciate if you keep them since I run Cortex-R52...

Cheers
Vladimir

>         Arnd
> 

Re: [PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Arnd Bergmann]

On Wed, Mar 9, 2022 at 5:21 PM Vladimir Murzin <vladimir.murzin@arm.com> wrote:
> On 3/9/22 4:17 PM, Arnd Bergmann wrote:
> > On Wed, Mar 9, 2022 at 4:48 PM Robin Murphy <robin.murphy@arm.com> wrote:
> >>
> >> On 2022-03-09 14:40, Arnd Bergmann wrote:
> >>> From: Arnd Bergmann <arnd@arndb.de>
> >>>
> >>> It is possible to build MMU-less kernels for Cortex-M base
> >>> microcrontrollers as well as a couple of older platforms that
> >>> have not been converted to CONFIG_ARCH_MULTIPLATFORM,
> >>> specifically ep93xx, footbridge, dove, sa1100 and s3c24xx.
> >>>
> >>> It seems unlikely that anybody has tested those configurations
> >>> in recent years, as even building them is frequently broken.
> >>> A patch I submitted caused another build time regression
> >>> in this configuration. I sent a patch for that, but it seems
> >>> better to also remove the option entirely, leaving ARMv7-M
> >>> as the only supported Arm NOMMU target for simplicity.
> >>
> >> In that case, it would probably make sense to garbage-collect all the
> >> configs, setup code and other stuff relating to older MMU-less CPU cores
> >> like ARM1156, ARM940, etc. at the same time.
> >
> > Right, good idea. These are only selected by CONFIG_ARCH_INTEGRATOR,
> > but that in turn doesn't build for CONFIG_MMU=n because it depends on
> > ARCH_MULTIPLATFORM. I'll send a patch for these.
> >
> > I also went back and forth between removing the #ifdefs in
> > arch/arm/mm/proc-*.S for this patch, though I did not do that in the end.
> > We may still want them at least for proc-v7.S because that is a small
> > chance that someone will want to support Cortex-R.
> >
>
> I'd appreciate if you keep them since I run Cortex-R52...

Ok, no problem.

Any opinion on removing CPU_ARM{7TDMI,740T,940T,946E}?

       Arnd

Re: [PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Linus Walleij]

On Wed, Mar 9, 2022 at 5:38 PM Arnd Bergmann <arnd@kernel.org> wrote:

> Any opinion on removing CPU_ARM{7TDMI,740T,940T,946E}?

7TDMI was/is extremely prolific, it is everywhere (such as in CSR/SiRF
GPS chips, SD cards, hard disks, a lot of sensors and what not).

That said I have never seen one of these systems with enough memory
to boot a recent Linux kernel. I think with the failure to push the kernel
footprint down (due to lack of interest) they don't really have a future as
Linux targets. They all run $small_os.

Yours,
Linus Walleij

Re: [PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Linus Walleij]

On Wed, Mar 9, 2022 at 5:17 PM Arnd Bergmann <arnd@kernel.org> wrote:
> Robin
> > In that case, it would probably make sense to garbage-collect all the
> > configs, setup code and other stuff relating to older MMU-less CPU cores
> > like ARM1156, ARM940, etc. at the same time.
>
> Right, good idea. These are only selected by CONFIG_ARCH_INTEGRATOR,
> but that in turn doesn't build for CONFIG_MMU=n because it depends on
> ARCH_MULTIPLATFORM. I'll send a patch for these.

Just delete these, I do have these CPU tiles around but they are so obscure
and I never got around to even testing to boot them.

Yours,
Linus Walleij

Re: [PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Arnd Bergmann]

On Thu, Mar 10, 2022 at 2:22 AM Linus Walleij <linus.walleij@linaro.org> wrote:
>
> On Wed, Mar 9, 2022 at 5:17 PM Arnd Bergmann <arnd@kernel.org> wrote:
> > Robin
> > > In that case, it would probably make sense to garbage-collect all the
> > > configs, setup code and other stuff relating to older MMU-less CPU cores
> > > like ARM1156, ARM940, etc. at the same time.
> >
> > Right, good idea. These are only selected by CONFIG_ARCH_INTEGRATOR,
> > but that in turn doesn't build for CONFIG_MMU=n because it depends on
> > ARCH_MULTIPLATFORM. I'll send a patch for these.
>
> Just delete these, I do have these CPU tiles around but they are so obscure
> and I never got around to even testing to boot them.

Right, of course you couldn't boot test them because it has been
impossible to even select them in Kconfig for years. I've added
a patch to completely remove the five v4/v5 NOMMU cores now,
will send that later.

There are five more cores that are only referenced by mach-integrator
that are supposed to work (922T, 1020, 1020E, 1022, 1026). Have you
ever tested those, or should we consider removing them as well?

At some point, there was a proposal to add an arm10 based SoC
to mainline, but that never happened and I'm fairly sure it won't
come back now.

        Arnd

Re: [PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Robin Murphy]

On 2022-03-10 09:23, Arnd Bergmann wrote:
> On Thu, Mar 10, 2022 at 2:22 AM Linus Walleij <linus.walleij@linaro.org> wrote:
>>
>> On Wed, Mar 9, 2022 at 5:17 PM Arnd Bergmann <arnd@kernel.org> wrote:
>>> Robin
>>>> In that case, it would probably make sense to garbage-collect all the
>>>> configs, setup code and other stuff relating to older MMU-less CPU cores
>>>> like ARM1156, ARM940, etc. at the same time.
>>>
>>> Right, good idea. These are only selected by CONFIG_ARCH_INTEGRATOR,
>>> but that in turn doesn't build for CONFIG_MMU=n because it depends on
>>> ARCH_MULTIPLATFORM. I'll send a patch for these.
>>
>> Just delete these, I do have these CPU tiles around but they are so obscure
>> and I never got around to even testing to boot them.
> 
> Right, of course you couldn't boot test them because it has been
> impossible to even select them in Kconfig for years. I've added
> a patch to completely remove the five v4/v5 NOMMU cores now,
> will send that later.
> 
> There are five more cores that are only referenced by mach-integrator
> that are supposed to work (922T, 1020, 1020E, 1022, 1026). Have you
> ever tested those, or should we consider removing them as well?
> 
> At some point, there was a proposal to add an arm10 based SoC
> to mainline, but that never happened and I'm fairly sure it won't
> come back now.

FWIW I have an Integrator/CM1026 that I'd love to play with purely for 
giggles, but it needs some serious archaeology to find and flash some 
firmware for it first.

I also have a couple of "real" ARM1026s in the form of Conexant 
Solos-based routers[1] which I've done a little hacking on, but don't 
see myself ever realistically having enough time or motivation to 
actually upstream anything. And at this point I don't see OpenWRT having 
any more interest in boards with only 15MB of RAM (yes, they really do 
boot with "mem=15M" to reserve 1MB for the modem...)

Cheers,
Robin.

[1] https://openwrt.org/toh/linksys/wag54g2

Re: [PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Linus Walleij]

On Thu, Mar 10, 2022 at 10:23 AM Arnd Bergmann <arnd@kernel.org> wrote:
> On Thu, Mar 10, 2022 at 2:22 AM Linus Walleij <linus.walleij@linaro.org> wrote:

> > Just delete these, I do have these CPU tiles around but they are so obscure
> > and I never got around to even testing to boot them.
>
> Right, of course you couldn't boot test them because it has been
> impossible to even select them in Kconfig for years.

Correct, I mean never got around to the whole cycle of "let's make this
thing boot" and then stumbling over things like that :D

> I've added
> a patch to completely remove the five v4/v5 NOMMU cores now,
> will send that later.

Excellent.

> There are five more cores that are only referenced by mach-integrator
> that are supposed to work (922T, 1020, 1020E, 1022, 1026). Have you
> ever tested those, or should we consider removing them as well?

Not the 10xx variants, but 920T and 922T I have tested and I
still have the tiles, while my favourite tile that is usually fitted is
ARM926EJ-S.

Yours,
Linus Walleij

Re: [PATCH 2/2] ARM: remove support for NOMMU ARMv4/v5

[Arnd Bergmann]

On Tue, Mar 15, 2022 at 12:00 AM Linus Walleij <linus.walleij@linaro.org> wrote:
> On Thu, Mar 10, 2022 at 10:23 AM Arnd Bergmann <arnd@kernel.org> wrote:
> > On Thu, Mar 10, 2022 at 2:22 AM Linus Walleij <linus.walleij@linaro.org> wrote:
>
> > > Just delete these, I do have these CPU tiles around but they are so obscure
> > > and I never got around to even testing to boot them.
> >
> > Right, of course you couldn't boot test them because it has been
> > impossible to even select them in Kconfig for years.
>
> Correct, I mean never got around to the whole cycle of "let's make this
> thing boot" and then stumbling over things like that :D
>
> > I've added
> > a patch to completely remove the five v4/v5 NOMMU cores now,
> > will send that later.
>
> Excellent.
>
> > There are five more cores that are only referenced by mach-integrator
> > that are supposed to work (922T, 1020, 1020E, 1022, 1026). Have you
> > ever tested those, or should we consider removing them as well?
>
> Not the 10xx variants, but 920T and 922T I have tested and I
> still have the tiles, while my favourite tile that is usually fitted is
> ARM926EJ-S.

Ok, then I would suggest we keep 922t and 1026 (which Robin mentioned)
but remove the others (1020,1020e, 1022).

     Arnd

Re: [PATCH 1/2] ARM: fix building NOMMU ARMv4/v5 kernels

[Linus Walleij]

On Wed, Mar 9, 2022 at 3:41 PM Arnd Bergmann <arnd@kernel.org> wrote:

> From: Arnd Bergmann <arnd@arndb.de>
>
> The removal of the old-style irq entry broke obscure NOMMU
> configurations on machines that have an MMU:
>
> ld.lld: error: undefined symbol: generic_handle_arch_irq
>  referenced by kernel/entry-armv.o:(__irq_svc) in archive arch/arm/built-in.a
>
> A follow-up patch to convert nvic to the generic_handle_arch_irq()
> could have fixed this by removing the Kconfig conditional, but did
> it differently.
>
> Change the Kconfig logic so ARM machines now unconditionally
> enable the feature.
>
> I have also submitted a patch to remove support for the configurations
> that broke, but fixing the regression first is a trivial and correct
> change.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Fixes: 54f481a2308e ("ARM: remove old-style irq entry")
> Fixes: 52d240871760 ("irqchip: nvic: Use GENERIC_IRQ_MULTI_HANDLER")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Thanks for fixing this so quickly!

Yours,
Linus Walleij

Re: [PATCH 1/2] ARM: fix building NOMMU ARMv4/v5 kernels

[Ard Biesheuvel]

On Wed, 9 Mar 2022 at 15:41, Arnd Bergmann <arnd@kernel.org> wrote:
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> The removal of the old-style irq entry broke obscure NOMMU
> configurations on machines that have an MMU:
>
> ld.lld: error: undefined symbol: generic_handle_arch_irq
>  referenced by kernel/entry-armv.o:(__irq_svc) in archive arch/arm/built-in.a
>
> A follow-up patch to convert nvic to the generic_handle_arch_irq()
> could have fixed this by removing the Kconfig conditional, but did
> it differently.
>
> Change the Kconfig logic so ARM machines now unconditionally
> enable the feature.
>
> I have also submitted a patch to remove support for the configurations
> that broke, but fixing the regression first is a trivial and correct
> change.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Fixes: 54f481a2308e ("ARM: remove old-style irq entry")
> Fixes: 52d240871760 ("irqchip: nvic: Use GENERIC_IRQ_MULTI_HANDLER")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Reviewed by: Ard Biesheuvel <ardb@kernel.org>

> ---
> This patch should go into the arm/devel-stable branch that has
> the arm-irq-and-vmap-stacks-for-rmk patches from Ard
> ---
>  arch/arm/Kconfig        | 2 +-
>  drivers/irqchip/Kconfig | 1 -
>  2 files changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index e9975ddd5034..5f0b40bab4fb 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -60,7 +60,7 @@ config ARM
>         select GENERIC_CPU_AUTOPROBE
>         select GENERIC_EARLY_IOREMAP
>         select GENERIC_IDLE_POLL_SETUP
> -       select GENERIC_IRQ_MULTI_HANDLER if MMU
> +       select GENERIC_IRQ_MULTI_HANDLER
>         select GENERIC_IRQ_PROBE
>         select GENERIC_IRQ_SHOW
>         select GENERIC_IRQ_SHOW_LEVEL
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index 488eaa14d3a7..7038957f4a77 100644
> --- a/drivers/irqchip/Kconfig
> +++ b/drivers/irqchip/Kconfig
> @@ -58,7 +58,6 @@ config ARM_NVIC
>         bool
>         select IRQ_DOMAIN_HIERARCHY
>         select GENERIC_IRQ_CHIP
> -       select GENERIC_IRQ_MULTI_HANDLER
>
>  config ARM_VIC
>         bool
> --
> 2.29.2
>