[PATCH v4 00/11] ARM: vf610m4: Add Vybrid Cortex-M4 support

[PATCH v4 00/11] ARM: vf610m4: Add Vybrid Cortex-M4 support

[Stefan Agner]

The fourth version has one small fix in the MSCM IR driver and
one dependency fix.

Like version 3 of the patchset, it does not contain the interrupt
router driver anymore (MSCM IR). The driver has been merged
inbetween:
https://lkml.org/lkml/2015/3/8/6

This patchset extends the NVIC driver to support irq domain
hierarchy and the MSCM IR driver to support NVIC as a parent irq
controller.

I'm happy with the outcome of the MSCM driver, the irq domain
hierarchy support has proven to work with GIC and NVIC as
intendet.

Since v2, this patchset also doesn't add any ARCH or SOC anymore.
Instead, it allows to select ARCH_MULTIPLATFORM in the !MMU case
and add ARCH_MULTI_V7M as a new CPU choice. This change is based
on patches found in Arnd's git tree, however, it tries to allow
MULTIPLATFORM with !MMU in a way which should not allow to make
other selections than before (except ARCH_MULTI_V7M of course).
This makes ARCH_MXC and SOC_VF610 available for the !MMU CPU V7M.
With a small change, SOC_VF610 is now selectable when the CPU
ARCH_MULTI_V7M is selected, and hence allows to build a kernel
for the Cortex-M4 CPU too.

The patchset has proven to be working on the Cortex-M4 of the
Vybrid SoC using a Colibri VF61 module.

Changes since v3:
- Added dependency IRQ_DOMAIN_HIERARCHY for ARM_NVIC
- Fix MSCM IR disable function check
- Remove "ARM: imx: depend MXC debug board on 3DS machines",
  the patch has been merged

Changes since v2:
- Update MSCM patches to merged version of MSCM interrupt router
- Use the GPLv2/X11 dual license in the new device tree files
- Drop SD controller in device tree (initramfs works now and is
  probably more appropriate for most cases)
- Disable GPIO nodes since the A5 is using them
- Drop CONFIG_ prefixes in Kconfig changes for MXC_DEBUG_BOARD
- Drop vector table resizing in favor of Maxime Coquelin's patch
  (https://lkml.org/lkml/2015/2/20/399)
- Remove !MMU dependency for ARCH_EFM32 since its part of
  ARCH_MULTI_V7M
- Rebased on v4.0-rc1

Changes since v1:
- Remove MSCM driver
- Support irq domain hierarchy with NVIC irq controller
- Extend MSCM interrupt router with NVIC as parent in the irq
  domain hierarchy 
- Rebased on v3.19-rc1 with MSCM driver
- NVIC: Register only the amount of IRQ's which vectors are
  available for

Changes since RFC:
- Unified addruart calls for MMU/!MMU
- Add MSCM support along with routable IRQ support in NVIC
- Rebased on Shawns for-next tree which made some changes
  obsolete (mainly the Vybrid SoC device tree files in for-next
  are already prepared for Cortex-M4 support)
- Removed SRC_GPR3 hack, this is now part of a mini boot-loader:
  https://github.com/falstaff84/vf610m4bootldr

Arnd Bergmann (1):
  ARM: efm32: move into multiplatform

Stefan Agner (10):
  genirq: generic chip: support hierarchy domain
  irqchip: nvic: support hierarchy irq domain
  irqchip: vf610-mscm: support NVIC parent
  ARM: ARMv7M: define size of vector table for Vybrid
  clocksource: add dependencies for Vybrid pit clocksource
  ARM: unify MMU/!MMU addruart calls
  ARM: allow MULTIPLATFORM with !MMU
  ARM: vf610: enable Cortex-M4 on Vybrid SoC
  ARM: dts: add support for Vybrid running on Cortex-M4
  ARM: vf610m4: add defconfig for Linux on Vybrids Cortex-M4

 Documentation/devicetree/bindings/arm/fsl.txt |  3 +
 arch/arm/Kconfig                              | 54 +++++++--------
 arch/arm/boot/dts/Makefile                    |  1 +
 arch/arm/boot/dts/vf610m4-colibri.dts         | 98 +++++++++++++++++++++++++++
 arch/arm/boot/dts/vf610m4.dtsi                | 50 ++++++++++++++
 arch/arm/configs/efm32_defconfig              |  2 +
 arch/arm/configs/vf610m4_defconfig            | 43 ++++++++++++
 arch/arm/include/debug/efm32.S                |  2 +-
 arch/arm/kernel/debug.S                       |  2 +-
 arch/arm/mach-imx/Kconfig                     | 36 ++++++----
 arch/arm/mach-imx/Makefile.boot               |  0
 arch/arm/mach-imx/mach-vf610.c                |  1 +
 arch/arm/mm/Kconfig                           |  1 +
 drivers/clocksource/Kconfig                   |  2 +
 drivers/irqchip/Kconfig                       |  1 +
 drivers/irqchip/irq-nvic.c                    | 28 +++++++-
 drivers/irqchip/irq-vf610-mscm-ir.c           | 32 +++++++--
 kernel/irq/generic-chip.c                     |  5 +-
 18 files changed, 306 insertions(+), 55 deletions(-)
 create mode 100644 arch/arm/boot/dts/vf610m4-colibri.dts
 create mode 100644 arch/arm/boot/dts/vf610m4.dtsi
 create mode 100644 arch/arm/configs/vf610m4_defconfig
 create mode 100644 arch/arm/mach-imx/Makefile.boot

-- 
2.3.5

[PATCH v4 01/11] genirq: generic chip: support hierarchy domain

[Stefan Agner]

Use the new helper function irq_domain_set_info to make sure the
function irq_domain_set_hwirq_and_chip is being called, which is
crucial to save irqdomain specific data to irq_data.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 kernel/irq/generic-chip.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/irq/generic-chip.c b/kernel/irq/generic-chip.c
index 61024e8..15b370d 100644
--- a/kernel/irq/generic-chip.c
+++ b/kernel/irq/generic-chip.c
@@ -360,7 +360,7 @@ static struct lock_class_key irq_nested_lock_class;
 int irq_map_generic_chip(struct irq_domain *d, unsigned int virq,
 			 irq_hw_number_t hw_irq)
 {
-	struct irq_data *data = irq_get_irq_data(virq);
+	struct irq_data *data = irq_domain_get_irq_data(d, virq);
 	struct irq_domain_chip_generic *dgc = d->gc;
 	struct irq_chip_generic *gc;
 	struct irq_chip_type *ct;
@@ -405,8 +405,7 @@ int irq_map_generic_chip(struct irq_domain *d, unsigned int virq,
 	else
 		data->mask = 1 << idx;
 
-	irq_set_chip_and_handler(virq, chip, ct->handler);
-	irq_set_chip_data(virq, gc);
+	irq_domain_set_info(d, virq, hw_irq, chip, gc, ct->handler, NULL, NULL);
 	irq_modify_status(virq, dgc->irq_flags_to_clear, dgc->irq_flags_to_set);
 	return 0;
 }
-- 
2.3.5

[PATCH v4 02/11] irqchip: nvic: support hierarchy irq domain

[Stefan Agner]

Add support for hierarchy irq domains. This is required to stack
the MSCM interrupt router and the NVIC controller found in Vybrid
SoC.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/irqchip/Kconfig    |  1 +
 drivers/irqchip/irq-nvic.c | 28 +++++++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index cc79d2a..ab8de26 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -30,6 +30,7 @@ config ARM_GIC_V3_ITS
 config ARM_NVIC
 	bool
 	select IRQ_DOMAIN
+	select IRQ_DOMAIN_HIERARCHY
 	select GENERIC_IRQ_CHIP
 
 config ARM_VIC
diff --git a/drivers/irqchip/irq-nvic.c b/drivers/irqchip/irq-nvic.c
index 4ff0805..5fac910 100644
--- a/drivers/irqchip/irq-nvic.c
+++ b/drivers/irqchip/irq-nvic.c
@@ -49,6 +49,31 @@ nvic_handle_irq(irq_hw_number_t hwirq, struct pt_regs *regs)
 	handle_IRQ(irq, regs);
 }
 
+static int nvic_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
+				unsigned int nr_irqs, void *arg)
+{
+	int i, ret;
+	irq_hw_number_t hwirq;
+	unsigned int type = IRQ_TYPE_NONE;
+	struct of_phandle_args *irq_data = arg;
+
+	ret = irq_domain_xlate_onecell(domain, irq_data->np, irq_data->args,
+				   irq_data->args_count, &hwirq, &type);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < nr_irqs; i++)
+		irq_map_generic_chip(domain, virq + i, hwirq + i);
+
+	return 0;
+}
+
+static const struct irq_domain_ops nvic_irq_domain_ops = {
+	.xlate = irq_domain_xlate_onecell,
+	.alloc = nvic_irq_domain_alloc,
+	.free = irq_domain_free_irqs_top,
+};
+
 static int __init nvic_of_init(struct device_node *node,
 			       struct device_node *parent)
 {
@@ -70,7 +95,8 @@ static int __init nvic_of_init(struct device_node *node,
 		irqs = NVIC_MAX_IRQ;
 
 	nvic_irq_domain =
-		irq_domain_add_linear(node, irqs, &irq_generic_chip_ops, NULL);
+		irq_domain_add_linear(node, irqs, &nvic_irq_domain_ops, NULL);
+
 	if (!nvic_irq_domain) {
 		pr_warn("Failed to allocate irq domain\n");
 		return -ENOMEM;
-- 
2.3.5

[PATCH v4 03/11] irqchip: vf610-mscm: support NVIC parent

[Stefan Agner]

Support the NVIC interrupt controller as node parent of the MSCM
interrupt router. On the dual-core variants of Vybird (VF6xx), the
NVIC interrupt controller is used by the Cortex-M4. To support
running Linux on this core too, MSCM needs NVIC parent support too.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/irqchip/irq-vf610-mscm-ir.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/irqchip/irq-vf610-mscm-ir.c b/drivers/irqchip/irq-vf610-mscm-ir.c
index 9521057..40b7d8d 100644
--- a/drivers/irqchip/irq-vf610-mscm-ir.c
+++ b/drivers/irqchip/irq-vf610-mscm-ir.c
@@ -47,6 +47,7 @@ struct vf610_mscm_ir_chip_data {
 	void __iomem *mscm_ir_base;
 	u16 cpu_mask;
 	u16 saved_irsprc[MSCM_IRSPRC_NUM];
+	bool is_nvic;
 };
 
 static struct vf610_mscm_ir_chip_data *mscm_ir_data;
@@ -91,6 +92,7 @@ static void vf610_mscm_ir_enable(struct irq_data *data)
 {
 	irq_hw_number_t hwirq = data->hwirq;
 	struct vf610_mscm_ir_chip_data *chip_data = data->chip_data;
+	struct irq_data *parent = data->parent_data;
 	u16 irsprc;
 
 	irsprc = readw_relaxed(chip_data->mscm_ir_base + MSCM_IRSPRC(hwirq));
@@ -101,17 +103,25 @@ static void vf610_mscm_ir_enable(struct irq_data *data)
 	writew_relaxed(chip_data->cpu_mask,
 		       chip_data->mscm_ir_base + MSCM_IRSPRC(hwirq));
 
-	irq_chip_unmask_parent(data);
+	if (parent->chip->irq_enable)
+		parent->chip->irq_enable(parent);
+	else
+		parent->chip->irq_unmask(parent);
+
 }
 
 static void vf610_mscm_ir_disable(struct irq_data *data)
 {
 	irq_hw_number_t hwirq = data->hwirq;
 	struct vf610_mscm_ir_chip_data *chip_data = data->chip_data;
+	struct irq_data *parent = data->parent_data;
 
 	writew_relaxed(0x0, chip_data->mscm_ir_base + MSCM_IRSPRC(hwirq));
 
-	irq_chip_mask_parent(data);
+	if (parent->chip->irq_disable)
+		parent->chip->irq_disable(parent);
+	else
+		parent->chip->irq_mask(parent);
 }
 
 static struct irq_chip vf610_mscm_ir_irq_chip = {
@@ -143,10 +153,17 @@ static int vf610_mscm_ir_domain_alloc(struct irq_domain *domain, unsigned int vi
 					      domain->host_data);
 
 	gic_data.np = domain->parent->of_node;
-	gic_data.args_count = 3;
-	gic_data.args[0] = GIC_SPI;
-	gic_data.args[1] = irq_data->args[0];
-	gic_data.args[2] = irq_data->args[1];
+
+	if (mscm_ir_data->is_nvic) {
+		gic_data.args_count = 1;
+		gic_data.args[0] = irq_data->args[0];
+	} else {
+		gic_data.args_count = 3;
+		gic_data.args[0] = GIC_SPI;
+		gic_data.args[1] = irq_data->args[0];
+		gic_data.args[2] = irq_data->args[1];
+	}
+
 	return irq_domain_alloc_irqs_parent(domain, virq, nr_irqs, &gic_data);
 }
 
@@ -199,6 +216,9 @@ static int __init vf610_mscm_ir_of_init(struct device_node *node,
 		goto out_unmap;
 	}
 
+	if (of_device_is_compatible(domain->parent->of_node, "arm,armv7m-nvic"))
+		mscm_ir_data->is_nvic = true;
+
 	cpu_pm_register_notifier(&mscm_ir_notifier_block);
 
 	return 0;
-- 
2.3.5

[PATCH v4 04/11] ARM: ARMv7M: define size of vector table for Vybrid

[Stefan Agner]

Vybrids has 112 peripherial interrupts which can be routed to the
Cortex-M4's NVIC interrupt controller.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 arch/arm/mm/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 16d077e..8eebc0d 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -609,6 +609,7 @@ config CPUV7M_NUM_IRQ
 	depends on CPU_V7M
 	default 90 if ARCH_STM32
 	default 38 if ARCH_EFM32
+	default 112 if SOC_VF610
 	default 240
 	help
 	  This option indicates the number of interrupts connected to the NVIC.
-- 
2.3.5

[PATCH v4 05/11] clocksource: add dependencies for Vybrid pit clocksource

[Stefan Agner]

Add the minimal dependencies required to use the Vybrid PIT
clocksource driver. Those are not part of the SoC dependencies.

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/clocksource/Kconfig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 1c2506f..350e742 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -164,6 +164,8 @@ config FSL_FTM_TIMER
 
 config VF_PIT_TIMER
 	bool
+	select CLKSRC_MMIO
+	select CLKSRC_OF
 	help
 	  Support for Period Interrupt Timer on Freescale Vybrid Family SoCs.
 
-- 
2.3.5

[PATCH v4 06/11] ARM: unify MMU/!MMU addruart calls

[Stefan Agner]

Remove the needless differences between MMU/!MMU addruart calls.
This allows to use the same addruart macro on SoC level. Useful
for SoC consisting of multiple CPUs with and without MMU such as
Freescale Vybrid.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 arch/arm/include/debug/efm32.S | 2 +-
 arch/arm/kernel/debug.S        | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/debug/efm32.S b/arch/arm/include/debug/efm32.S
index 2265a19..660fa1e 100644
--- a/arch/arm/include/debug/efm32.S
+++ b/arch/arm/include/debug/efm32.S
@@ -16,7 +16,7 @@
 
 #define	UARTn_TXDATA		0x0034
 
-		.macro	addruart, rx, tmp
+		.macro	addruart, rx, tmp, tmp2
 		ldr	\rx, =(CONFIG_DEBUG_UART_PHYS)
 
 		/*
diff --git a/arch/arm/kernel/debug.S b/arch/arm/kernel/debug.S
index 78c91b5..ea9646c 100644
--- a/arch/arm/kernel/debug.S
+++ b/arch/arm/kernel/debug.S
@@ -35,7 +35,7 @@
 
 #else /* !CONFIG_MMU */
 		.macro	addruart_current, rx, tmp1, tmp2
-		addruart	\rx, \tmp1
+		addruart	\rx, \tmp1, \tmp2
 		.endm
 
 #endif /* CONFIG_MMU */
-- 
2.3.5

[PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Stefan Agner]

In order to support SoC with heterogenous CPU architectures (such
as Freescale Vybrid/i.MXSX) it is preferable to use the same
architecture (ARCH_MXC in this case) for the MMU enabled and !MMU
CPU. Hence allow to select MULTIPLATFORM even without MMU.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 arch/arm/Kconfig | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 9f1f09a..636cb3f 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -230,7 +230,7 @@ config VECTORS_BASE
 	  in size.
 
 config ARM_PATCH_PHYS_VIRT
-	bool "Patch physical to virtual translations at runtime" if EMBEDDED
+	bool "Patch physical to virtual translations at runtime" if EMBEDDED || (ARCH_MULTIPLATFORM && MMU)
 	default y
 	depends on !XIP_KERNEL && MMU
 	depends on !ARCH_REALVIEW || !SPARSEMEM
@@ -305,15 +305,12 @@ config MMU
 #
 choice
 	prompt "ARM system type"
-	default ARCH_VERSATILE if !MMU
-	default ARCH_MULTIPLATFORM if MMU
+	default ARCH_MULTIPLATFORM
 
 config ARCH_MULTIPLATFORM
 	bool "Allow multiple platforms to be selected"
-	depends on MMU
 	select ARCH_WANT_OPTIONAL_GPIOLIB
 	select ARM_HAS_SG_CHAIN
-	select ARM_PATCH_PHYS_VIRT
 	select AUTO_ZRELADDR
 	select CLKSRC_OF
 	select COMMON_CLK
@@ -785,13 +782,13 @@ comment "CPU Core family selection"
 
 config ARCH_MULTI_V4
 	bool "ARMv4 based platforms (FA526)"
-	depends on !ARCH_MULTI_V6_V7
+	depends on !ARCH_MULTI_V6_V7 && MMU
 	select ARCH_MULTI_V4_V5
 	select CPU_FA526
 
 config ARCH_MULTI_V4T
 	bool "ARMv4T based platforms (ARM720T, ARM920T, ...)"
-	depends on !ARCH_MULTI_V6_V7
+	depends on !ARCH_MULTI_V6_V7 && MMU
 	select ARCH_MULTI_V4_V5
 	select CPU_ARM920T if !(CPU_ARM7TDMI || CPU_ARM720T || \
 		CPU_ARM740T || CPU_ARM9TDMI || CPU_ARM922T || \
@@ -799,7 +796,7 @@ config ARCH_MULTI_V4T
 
 config ARCH_MULTI_V5
 	bool "ARMv5 based platforms (ARM926T, XSCALE, PJ1, ...)"
-	depends on !ARCH_MULTI_V6_V7
+	depends on !ARCH_MULTI_V6_V7 && MMU
 	select ARCH_MULTI_V4_V5
 	select CPU_ARM926T if !(CPU_ARM946E || CPU_ARM1020 || \
 		CPU_ARM1020E || CPU_ARM1022 || CPU_ARM1026 || \
@@ -810,11 +807,13 @@ config ARCH_MULTI_V4_V5
 
 config ARCH_MULTI_V6
 	bool "ARMv6 based platforms (ARM11)"
+	depends on MMU
 	select ARCH_MULTI_V6_V7
 	select CPU_V6K
 
 config ARCH_MULTI_V7
-	bool "ARMv7 based platforms (Cortex-A, PJ4, Scorpion, Krait)"
+	bool "ARMv7-A based platforms (Cortex-A, PJ4, Scorpion, Krait)"
+	depends on MMU
 	default y
 	select ARCH_MULTI_V6_V7
 	select CPU_V7
@@ -825,7 +824,7 @@ config ARCH_MULTI_V6_V7
 	select MIGHT_HAVE_CACHE_L2X0
 
 config ARCH_MULTI_CPU_AUTO
-	def_bool !(ARCH_MULTI_V4 || ARCH_MULTI_V4T || ARCH_MULTI_V6_V7)
+	def_bool !(ARCH_MULTI_V4 || ARCH_MULTI_V4T || ARCH_MULTI_V6_V7) && MMU
 	select ARCH_MULTI_V5
 
 endmenu
@@ -1967,7 +1966,7 @@ endchoice
 
 config XIP_KERNEL
 	bool "Kernel Execute-In-Place from ROM"
-	depends on !ARM_LPAE && !ARCH_MULTIPLATFORM
+	depends on !ARM_LPAE && (!ARCH_MULTIPLATFORM || ARCH_MULTI_V7M)
 	help
 	  Execute-In-Place allows the kernel to run from non-volatile storage
 	  directly addressable by the CPU, such as NOR flash. This saves RAM
-- 
2.3.5

[PATCH v4 08/11] ARM: efm32: move into multiplatform

[Stefan Agner]

From: Arnd Bergmann <arnd@arndb.de>

Since the multiplatform configuration can support no-MMU kernels now,
there is nothing stopping us from moving the efm32 platform in there
as well. This introduces a new ARCH_MULTI_V7M CPU architecture selection
option, since v7-M is incompatible with v7-A, and we can have either
of the two enabled for multiplatform, but not both at the same time.

Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 arch/arm/Kconfig                 | 33 ++++++++++++++-------------------
 arch/arm/configs/efm32_defconfig |  2 ++
 2 files changed, 16 insertions(+), 19 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 636cb3f..51d1750 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -316,7 +316,7 @@ config ARCH_MULTIPLATFORM
 	select COMMON_CLK
 	select GENERIC_CLOCKEVENTS
 	select MIGHT_HAVE_PCI
-	select MULTI_IRQ_HANDLER
+	select MULTI_IRQ_HANDLER if !ARCH_MULTI_V7M
 	select SPARSE_IRQ
 	select USE_OF
 
@@ -402,24 +402,6 @@ config ARCH_EBSA110
 	  Ethernet interface, two PCMCIA sockets, two serial ports and a
 	  parallel port.
 
-config ARCH_EFM32
-	bool "Energy Micro efm32"
-	depends on !MMU
-	select ARCH_REQUIRE_GPIOLIB
-	select ARM_NVIC
-	select AUTO_ZRELADDR
-	select CLKSRC_OF
-	select COMMON_CLK
-	select CPU_V7M
-	select GENERIC_CLOCKEVENTS
-	select NO_DMA
-	select NO_IOPORT_MAP
-	select SPARSE_IRQ
-	select USE_OF
-	help
-	  Support for Energy Micro's (now Silicon Labs) efm32 Giant Gecko
-	  processors.
-
 config ARCH_EP93XX
 	bool "EP93xx-based"
 	select ARCH_HAS_HOLES_MEMORYMODEL
@@ -780,6 +762,13 @@ menu "Multiple platform selection"
 
 comment "CPU Core family selection"
 
+config ARCH_MULTI_V7M
+	bool "ARMv7-M based platforms (Cortex-M)"
+	depends on !MMU && !(ARCH_MULTI_V4_V5 || ARCH_MULTI_V6_V7)
+	select CPU_V7M
+	select ARM_NVIC
+	select NO_IOPORT_MAP
+
 config ARCH_MULTI_V4
 	bool "ARMv4 based platforms (FA526)"
 	depends on !ARCH_MULTI_V6_V7 && MMU
@@ -836,6 +825,12 @@ config ARCH_VIRT
 	select ARM_PSCI
 	select HAVE_ARM_ARCH_TIMER
 
+config ARCH_EFM32
+	bool "Energy Micro efm32" if ARCH_MULTI_V7M
+	help
+	  Support for Energy Micro's (now Silicon Labs) efm32 Giant Gecko
+	  processors.
+
 #
 # This is sorted alphabetically by mach-* pathname.  However, plat-*
 # Kconfigs may be included either alphabetically (according to the
diff --git a/arch/arm/configs/efm32_defconfig b/arch/arm/configs/efm32_defconfig
index c4c17e3..f58cb28 100644
--- a/arch/arm/configs/efm32_defconfig
+++ b/arch/arm/configs/efm32_defconfig
@@ -16,6 +16,8 @@ CONFIG_EMBEDDED=y
 # CONFIG_IOSCHED_DEADLINE is not set
 # CONFIG_IOSCHED_CFQ is not set
 # CONFIG_MMU is not set
+# CONFIG_ARCH_MULTI_V7 is not set
+CONFIG_ARCH_MULTI_V7M=y
 CONFIG_ARCH_EFM32=y
 CONFIG_SET_MEM_PARAM=y
 CONFIG_DRAM_BASE=0x88000000
-- 
2.3.5

[PATCH v4 09/11] ARM: vf610: enable Cortex-M4 on Vybrid SoC

[Stefan Agner]

This patch allows to build the Kernel for Vybrid (VF6xx) SoC
when ARMv7-M CPU is selected. The resulting image runs on the
secondary Cortex-M4 core. This core has equally access to all
peripherals as the main Cortex-A5 core. However, there is no
resource control mechanism, hence when both cores are used
simultaneously, orthogonal device tree's are required.

The boot CPU is dependent on the SoC variant, however the
commonly available boards use variants where the Cortex-A5 is
the primary/boot CPU. Booting the secondary Cortex-M4 CPU
needs SoC specific register written. There is no in kernel
support for this right now, a external userspace utility
called "m4boot" can be used to boot the kernel:

m4boot xipImage initramfs.cpio.lzo vf610m4-colibri.dtb

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 Documentation/devicetree/bindings/arm/fsl.txt |  3 +++
 arch/arm/mach-imx/Kconfig                     | 36 +++++++++++++++++----------
 arch/arm/mach-imx/Makefile.boot               |  0
 arch/arm/mach-imx/mach-vf610.c                |  1 +
 4 files changed, 27 insertions(+), 13 deletions(-)
 create mode 100644 arch/arm/mach-imx/Makefile.boot

diff --git a/Documentation/devicetree/bindings/arm/fsl.txt b/Documentation/devicetree/bindings/arm/fsl.txt
index a5462b6..2a3ba73 100644
--- a/Documentation/devicetree/bindings/arm/fsl.txt
+++ b/Documentation/devicetree/bindings/arm/fsl.txt
@@ -81,12 +81,15 @@ Freescale Vybrid Platform Device Tree Bindings
 For the Vybrid SoC familiy all variants with DDR controller are supported,
 which is the VF5xx and VF6xx series. Out of historical reasons, in most
 places the kernel uses vf610 to refer to the whole familiy.
+The compatible string "fsl,vf610m4" is used for the secondary Cortex-M4
+core support.
 
 Required root node compatible property (one of them):
     - compatible = "fsl,vf500";
     - compatible = "fsl,vf510";
     - compatible = "fsl,vf600";
     - compatible = "fsl,vf610";
+    - compatible = "fsl,vf610m4";
 
 Freescale LS1021A Platform Device Tree Bindings
 ------------------------------------------------
diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig
index c8dffce..b29ade8 100644
--- a/arch/arm/mach-imx/Kconfig
+++ b/arch/arm/mach-imx/Kconfig
@@ -1,5 +1,5 @@
 menuconfig ARCH_MXC
-	bool "Freescale i.MX family" if ARCH_MULTI_V4_V5 || ARCH_MULTI_V6_V7
+	bool "Freescale i.MX family" if ARCH_MULTI_V4_V5 || ARCH_MULTI_V6_V7 || ARCH_MULTI_V7M
 	select ARCH_REQUIRE_GPIOLIB
 	select ARM_CPU_SUSPEND if PM
 	select CLKSRC_MMIO
@@ -557,9 +557,11 @@ config MACH_VPR200
 
 endif
 
+comment "Device tree only"
+
 if ARCH_MULTI_V7
 
-comment "Device tree only"
+comment "Cortex-A platforms"
 
 config SOC_IMX5
 	bool
@@ -629,10 +631,28 @@ config SOC_IMX6SX
 	help
 	  This enables support for Freescale i.MX6 SoloX processor.
 
+
+config SOC_LS1021A
+	bool "Freescale LS1021A support"
+	select ARM_GIC
+	select HAVE_ARM_ARCH_TIMER
+	select PCI_DOMAINS if PCI
+	select ZONE_DMA if ARM_LPAE
+
+	help
+	  This enable support for Freescale LS1021A processor.
+
+endif
+
+comment "Cortex-A/Cortex-M asymmetric multiprocessing platforms"
+
+if ARCH_MULTI_V7 || ARCH_MULTI_V7M
+
 config SOC_VF610
 	bool "Vybrid Family VF610 support"
 	select IRQ_DOMAIN_HIERARCHY
-	select ARM_GIC
+	select ARM_GIC if ARCH_MULTI_V7
+	select ARM_NVIC if ARCH_MULTI_V7M
 	select PINCTRL_VF610
 	select PL310_ERRATA_769419 if CACHE_L2X0
 
@@ -659,16 +679,6 @@ choice
 
 endchoice
 
-config SOC_LS1021A
-	bool "Freescale LS1021A support"
-	select ARM_GIC
-	select HAVE_ARM_ARCH_TIMER
-	select PCI_DOMAINS if PCI
-	select ZONE_DMA if ARM_LPAE
-
-	help
-	  This enable support for Freescale LS1021A processor.
-
 endif
 
 source "arch/arm/mach-imx/devices/Kconfig"
diff --git a/arch/arm/mach-imx/Makefile.boot b/arch/arm/mach-imx/Makefile.boot
new file mode 100644
index 0000000..e69de29
diff --git a/arch/arm/mach-imx/mach-vf610.c b/arch/arm/mach-imx/mach-vf610.c
index 2e7c75b..b20f6c1 100644
--- a/arch/arm/mach-imx/mach-vf610.c
+++ b/arch/arm/mach-imx/mach-vf610.c
@@ -17,6 +17,7 @@ static const char * const vf610_dt_compat[] __initconst = {
 	"fsl,vf510",
 	"fsl,vf600",
 	"fsl,vf610",
+	"fsl,vf610m4",
 	NULL,
 };
 
-- 
2.3.5

[PATCH v4 10/11] ARM: dts: add support for Vybrid running on Cortex-M4

[Stefan Agner]

This adds an initial device tree to run Linux on the Cortex-M4 on
the Vybrid based Colibri VF61 module.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 arch/arm/boot/dts/Makefile            |  1 +
 arch/arm/boot/dts/vf610m4-colibri.dts | 98 +++++++++++++++++++++++++++++++++++
 arch/arm/boot/dts/vf610m4.dtsi        | 50 ++++++++++++++++++
 3 files changed, 149 insertions(+)
 create mode 100644 arch/arm/boot/dts/vf610m4-colibri.dts
 create mode 100644 arch/arm/boot/dts/vf610m4.dtsi

diff --git a/arch/arm/boot/dts/Makefile b/arch/arm/boot/dts/Makefile
index a1c776b..3a6ff9f 100644
--- a/arch/arm/boot/dts/Makefile
+++ b/arch/arm/boot/dts/Makefile
@@ -309,6 +309,7 @@ dtb-$(CONFIG_SOC_LS1021A) += \
 dtb-$(CONFIG_SOC_VF610) += \
 	vf500-colibri-eval-v3.dtb \
 	vf610-colibri-eval-v3.dtb \
+	vf610m4-colibri.dtb \
 	vf610-cosmic.dtb \
 	vf610-twr.dtb
 dtb-$(CONFIG_ARCH_MXS) += \
diff --git a/arch/arm/boot/dts/vf610m4-colibri.dts b/arch/arm/boot/dts/vf610m4-colibri.dts
new file mode 100644
index 0000000..acd6cb5
--- /dev/null
+++ b/arch/arm/boot/dts/vf610m4-colibri.dts
@@ -0,0 +1,98 @@
+/*
+ * Device tree for Colibri VF61 Cortex-M4 support
+ *
+ * Copyright (C) 2015 Stefan Agner
+ *
+ * This file is dual-licensed: you can use it either under the terms
+ * of the GPL or the X11 license, at your option. Note that this dual
+ * licensing only applies to this file, and not this project as a
+ * whole.
+ *
+ *  a) This file is free software; you can redistribute it and/or
+ *     modify it under the terms of the GNU General Public License as
+ *     published by the Free Software Foundation; either version 2 of the
+ *     License, or (at your option) any later version.
+ *
+ *     This file is distributed in the hope that it will be useful
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ * Or, alternatively
+ *
+ *  b) Permission is hereby granted, free of charge, to any person
+ *     obtaining a copy of this software and associated documentation
+ *     files (the "Software"), to deal in the Software without
+ *     restriction, including without limitation the rights to use
+ *     copy, modify, merge, publish, distribute, sublicense, and/or
+ *     sell copies of the Software, and to permit persons to whom the
+ *     Software is furnished to do so, subject to the following
+ *     conditions:
+ *
+ *     The above copyright notice and this permission notice shall be
+ *     included in all copies or substantial portions of the Software.
+ *
+ *     THE SOFTWARE IS PROVIDED , WITHOUT WARRANTY OF ANY KIND
+ *     EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ *     OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ *     NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ *     HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY
+ *     WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ *     FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ *     OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/dts-v1/;
+#include "vf610m4.dtsi"
+
+/ {
+	model = "VF610 Cortex-M4";
+	compatible = "fsl,vf610m4";
+
+	chosen {
+		bootargs = "console=ttyLP2,115200 clk_ignore_unused init=/linuxrc rw";
+	};
+
+	memory {
+		reg = <0x8c000000 0x3000000>;
+	};
+};
+
+&gpio0 {
+	status = "disabled";
+};
+
+&gpio1 {
+	status = "disabled";
+};
+
+&gpio2 {
+	status = "disabled";
+};
+
+&gpio3 {
+	status = "disabled";
+};
+
+&gpio4 {
+	status = "disabled";
+};
+
+&uart2 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_uart2>;
+	status = "okay";
+};
+
+&iomuxc {
+	vf610-colibri {
+		pinctrl_uart2: uart2grp {
+			fsl,pins = <
+				VF610_PAD_PTD0__UART2_TX		0x21a2
+				VF610_PAD_PTD1__UART2_RX		0x21a1
+				VF610_PAD_PTD2__UART2_RTS		0x21a2
+				VF610_PAD_PTD3__UART2_CTS		0x21a1
+			>;
+		};
+	};
+};
diff --git a/arch/arm/boot/dts/vf610m4.dtsi b/arch/arm/boot/dts/vf610m4.dtsi
new file mode 100644
index 0000000..9ffe2eb
--- /dev/null
+++ b/arch/arm/boot/dts/vf610m4.dtsi
@@ -0,0 +1,50 @@
+/*
+ * Device tree for VF6xx Cortex-M4 support
+ *
+ * Copyright (C) 2015 Stefan Agner
+ *
+ * This file is dual-licensed: you can use it either under the terms
+ * of the GPL or the X11 license, at your option. Note that this dual
+ * licensing only applies to this file, and not this project as a
+ * whole.
+ *
+ *  a) This file is free software; you can redistribute it and/or
+ *     modify it under the terms of the GNU General Public License as
+ *     published by the Free Software Foundation; either version 2 of the
+ *     License, or (at your option) any later version.
+ *
+ *     This file is distributed in the hope that it will be useful
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ * Or, alternatively
+ *
+ *  b) Permission is hereby granted, free of charge, to any person
+ *     obtaining a copy of this software and associated documentation
+ *     files (the "Software"), to deal in the Software without
+ *     restriction, including without limitation the rights to use
+ *     copy, modify, merge, publish, distribute, sublicense, and/or
+ *     sell copies of the Software, and to permit persons to whom the
+ *     Software is furnished to do so, subject to the following
+ *     conditions:
+ *
+ *     The above copyright notice and this permission notice shall be
+ *     included in all copies or substantial portions of the Software.
+ *
+ *     THE SOFTWARE IS PROVIDED , WITHOUT WARRANTY OF ANY KIND
+ *     EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ *     OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ *     NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ *     HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY
+ *     WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ *     FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ *     OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include "armv7-m.dtsi"
+#include "vfxxx.dtsi"
+
+&mscm_ir {
+	interrupt-parent = <&nvic>;
+};
-- 
2.3.5

[PATCH v4 11/11] ARM: vf610m4: add defconfig for Linux on Vybrids Cortex-M4

[Stefan Agner]

Add defconfig for Linux on Vybrid (vf610) on the secondary Cortex-
M4 CPU. The use of a XIP image has been tested which needs to be
loaded (e.g. using the custom m4boot loader) to the end of the
available RAM at address 0x8f000000. The Cortex-M4 has a code-alias
which makes sure that the instructions get fetched through the code
bus (alias starts at 0x00800000 => 0x80800000 in system address).
Hence, to get optimal performance, use 0x0f000000 as XIP_PHYS_ADDR.
This address is additionally shifted by the length of the minimal
loader which is inserted by m4boot. Currently, this offset is 0x80.

The standard DRAM base address is configured to 0x8C000000, which
gives the Cortex-M4 48MiB of RAM.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 arch/arm/configs/vf610m4_defconfig | 43 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 arch/arm/configs/vf610m4_defconfig

diff --git a/arch/arm/configs/vf610m4_defconfig b/arch/arm/configs/vf610m4_defconfig
new file mode 100644
index 0000000..b00015c
--- /dev/null
+++ b/arch/arm/configs/vf610m4_defconfig
@@ -0,0 +1,43 @@
+CONFIG_NAMESPACES=y
+CONFIG_BLK_DEV_INITRD=y
+# CONFIG_RD_BZIP2 is not set
+# CONFIG_RD_LZMA is not set
+# CONFIG_RD_XZ is not set
+# CONFIG_RD_LZ4 is not set
+CONFIG_KALLSYMS_ALL=y
+CONFIG_EMBEDDED=y
+# CONFIG_MMU is not set
+CONFIG_ARCH_MULTI_V7M=y
+CONFIG_ARCH_MXC=y
+CONFIG_SOC_VF610=y
+CONFIG_VF_USE_PIT_TIMER=y
+CONFIG_SET_MEM_PARAM=y
+CONFIG_DRAM_BASE=0x8c000000
+CONFIG_FLASH_MEM_BASE=0x8f000000
+CONFIG_FLASH_SIZE=0x01000000
+CONFIG_CMDLINE="console=/dev/ttyLP2"
+CONFIG_XIP_KERNEL=y
+CONFIG_XIP_PHYS_ADDR=0x0f000080
+CONFIG_BINFMT_FLAT=y
+CONFIG_BINFMT_ZFLAT=y
+CONFIG_BINFMT_SHARED_FLAT=y
+# CONFIG_SUSPEND is not set
+# CONFIG_UEVENT_HELPER is not set
+# CONFIG_STANDALONE is not set
+# CONFIG_PREVENT_FIRMWARE_BUILD is not set
+# CONFIG_FIRMWARE_IN_KERNEL is not set
+# CONFIG_ALLOW_DEV_COREDUMP is not set
+CONFIG_BLK_DEV_RAM=y
+CONFIG_BLK_DEV_RAM_COUNT=4
+# CONFIG_INPUT_MOUSEDEV is not set
+# CONFIG_KEYBOARD_ATKBD is not set
+# CONFIG_INPUT_MOUSE is not set
+# CONFIG_SERIO is not set
+CONFIG_SERIAL_FSL_LPUART=y
+CONFIG_SERIAL_FSL_LPUART_CONSOLE=y
+# CONFIG_HW_RANDOM is not set
+CONFIG_MFD_SYSCON=y
+# CONFIG_HID is not set
+# CONFIG_USB_SUPPORT is not set
+# CONFIG_MISC_FILESYSTEMS is not set
+# CONFIG_FTRACE is not set
-- 
2.3.5

Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Russell King - ARM Linux]

On Fri, Apr 03, 2015 at 09:44:48PM +0200, Stefan Agner wrote:
> In order to support SoC with heterogenous CPU architectures (such
> as Freescale Vybrid/i.MXSX) it is preferable to use the same
> architecture (ARCH_MXC in this case) for the MMU enabled and !MMU
> CPU. Hence allow to select MULTIPLATFORM even without MMU.
> 
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---
>  arch/arm/Kconfig | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 9f1f09a..636cb3f 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -230,7 +230,7 @@ config VECTORS_BASE
>  	  in size.
>  
>  config ARM_PATCH_PHYS_VIRT
> -	bool "Patch physical to virtual translations at runtime" if EMBEDDED
> +	bool "Patch physical to virtual translations at runtime" if EMBEDDED || (ARCH_MULTIPLATFORM && MMU)
>  	default y

This makes no sense.  Multiplatform MMU _requires_ this feature, so why
offer it to the user when multiplatform is enabled _and_ MMU is enabled?

Patch 7817/1 in the patch system tried doing something like you're trying
to do here - I wonder whether you've reviewed the mailing list for
previous discussions.

Given that it's Easter, I'm not going to re-state what I said last time
this came up, but instead leave you to do some research.  For example,
reading message id <20130819232411.GX23006@n2100.arm.linux.org.uk>...

Thanks.

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.

Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Stefan Agner]

On 2015-04-03 22:09, Russell King - ARM Linux wrote:
> On Fri, Apr 03, 2015 at 09:44:48PM +0200, Stefan Agner wrote:
>> In order to support SoC with heterogenous CPU architectures (such
>> as Freescale Vybrid/i.MXSX) it is preferable to use the same
>> architecture (ARCH_MXC in this case) for the MMU enabled and !MMU
>> CPU. Hence allow to select MULTIPLATFORM even without MMU.
>>
>> Signed-off-by: Stefan Agner <stefan@agner.ch>
>> ---
>>  arch/arm/Kconfig | 21 ++++++++++-----------
>>  1 file changed, 10 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> index 9f1f09a..636cb3f 100644
>> --- a/arch/arm/Kconfig
>> +++ b/arch/arm/Kconfig
>> @@ -230,7 +230,7 @@ config VECTORS_BASE
>>  	  in size.
>>
>>  config ARM_PATCH_PHYS_VIRT
>> -	bool "Patch physical to virtual translations at runtime" if EMBEDDED
>> +	bool "Patch physical to virtual translations at runtime" if EMBEDDED || (ARCH_MULTIPLATFORM && MMU)
>>  	default y
> 
> This makes no sense.  Multiplatform MMU _requires_ this feature, so why
> offer it to the user when multiplatform is enabled _and_ MMU is enabled?

I see, this is plain wrong. Will replace that with a select ... if MMU
in multiplatform.

> Patch 7817/1 in the patch system tried doing something like you're trying
> to do here - I wonder whether you've reviewed the mailing list for
> previous discussions.

I did some research at RFC/v1 time and mainly looked into Arnd's git
trees. Most patches just open up !MMU for multiplatform. What I'm trying
to do here is to enable !MMU with multiplatform while keeping the impact
as little as possible, e.g. by making all other platforms in
multiplatform dependent on MMU.

See also
https://www.marc.info/?l=linux-kernel&m=141997848124399&w=2

> Given that it's Easter, I'm not going to re-state what I said last time
> this came up, but instead leave you to do some research.  For example,
> reading message id <20130819232411.GX23006@n2100.arm.linux.org.uk>...

Also looked at some other messages about this topic, but I guess quotes
from the message above will do to discuss this further:
> Now, here's the question: can multiplatform ever work properly on nommu?
> 
> We get multiplatform working on MMU by using the MMU to provide a more
> consistent view of the system.  On noMMU, we don't have that.  So if
> your kernel is built to run assuming that it will be located in ram at
> location X on platform Y, that isn't going to work if platform Z doesn't
> have RAM there.

The platforms I primarily have in mind (heterogeneous multi-processing
SoC's with MMU/!MMU processors) would actually allow such a
multiplatform kernel: i.MX6 SoloX as well as Vybrid have the main memory
in the same location, hence one could build a multiplatform !MMU kernel
for this two devices. Of course, this is possible more by chance. I also
did not tried it yet. I don't have a i.MX6 SoloX device.

> My feeling is that the motivation behind this patch is to avoid an
> amount of yuckyness associated with trying to enable Versatile Express
> support outside of the multiplatform container - it's not really about
> being able to build a single zImage which works on all noMMU platforms.
> So, I don't think this is the right solution to this problem.

I must admit that this was the main motivation for me too. My first
approach was to create a set of completely independent config symbols:
http://marc.info/?l=linux-arm-kernel&m=141756604900611&w=2

However, I'm sure this could be done better and with less config
symbols.

So, if you think it would be worth enabling multiplatform for these
devices (Vybrid/i.MX6 SoloX), I would prepare a patchset which does it
while not converting EFM32 to multiplatform (as patch 08/11 currently
does).

If you think it's also not worth for those devices, I will try to enable
ARCH_MXC/SOC_VF610 with !MMU and !MULTIPLATFORM...

--
Stefan

Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Russell King - ARM Linux]

On Sat, Apr 04, 2015 at 01:56:20AM +0200, Stefan Agner wrote:
> On 2015-04-03 22:09, Russell King - ARM Linux wrote:
> > On Fri, Apr 03, 2015 at 09:44:48PM +0200, Stefan Agner wrote:
> >> In order to support SoC with heterogenous CPU architectures (such
> >> as Freescale Vybrid/i.MXSX) it is preferable to use the same
> >> architecture (ARCH_MXC in this case) for the MMU enabled and !MMU
> >> CPU. Hence allow to select MULTIPLATFORM even without MMU.
> >>
> >> Signed-off-by: Stefan Agner <stefan@agner.ch>
> >> ---
> >>  arch/arm/Kconfig | 21 ++++++++++-----------
> >>  1 file changed, 10 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> >> index 9f1f09a..636cb3f 100644
> >> --- a/arch/arm/Kconfig
> >> +++ b/arch/arm/Kconfig
> >> @@ -230,7 +230,7 @@ config VECTORS_BASE
> >>  	  in size.
> >>
> >>  config ARM_PATCH_PHYS_VIRT
> >> -	bool "Patch physical to virtual translations at runtime" if EMBEDDED
> >> +	bool "Patch physical to virtual translations at runtime" if EMBEDDED || (ARCH_MULTIPLATFORM && MMU)
> >>  	default y
> > 
> > This makes no sense.  Multiplatform MMU _requires_ this feature, so why
> > offer it to the user when multiplatform is enabled _and_ MMU is enabled?
> 
> I see, this is plain wrong. Will replace that with a select ... if MMU
> in multiplatform.

I think what I'd like to see is, in the top level choice:

config ARM_SINGLE_ARMV7M
	bool "ARM architecture v7M compliant (Cortex-M0/M3/M4) SoC"
	depends on !MMU
	select ARM_NVIC
	... etc ...

which then allows a /multiplatform/ v7M kernel to be built, allowing the
selection of EFM32, SOC_VF610, and any other v7M compliant SoC.

So, it's very similar to multiplatform in the sense that several SoCs
can be built together, but we preserve the need not to build
incompatible stuff together.

Thoughts?

-- 
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according to speedtest.net.

Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Stefan Agner]

On 2015-04-05 18:10, Russell King - ARM Linux wrote:
> On Sat, Apr 04, 2015 at 01:56:20AM +0200, Stefan Agner wrote:
>> On 2015-04-03 22:09, Russell King - ARM Linux wrote:
>> > On Fri, Apr 03, 2015 at 09:44:48PM +0200, Stefan Agner wrote:
>> >> In order to support SoC with heterogenous CPU architectures (such
>> >> as Freescale Vybrid/i.MXSX) it is preferable to use the same
>> >> architecture (ARCH_MXC in this case) for the MMU enabled and !MMU
>> >> CPU. Hence allow to select MULTIPLATFORM even without MMU.
>> >>
>> >> Signed-off-by: Stefan Agner <stefan@agner.ch>
>> >> ---
>> >>  arch/arm/Kconfig | 21 ++++++++++-----------
>> >>  1 file changed, 10 insertions(+), 11 deletions(-)
>> >>
>> >> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> >> index 9f1f09a..636cb3f 100644
>> >> --- a/arch/arm/Kconfig
>> >> +++ b/arch/arm/Kconfig
>> >> @@ -230,7 +230,7 @@ config VECTORS_BASE
>> >>  	  in size.
>> >>
>> >>  config ARM_PATCH_PHYS_VIRT
>> >> -	bool "Patch physical to virtual translations at runtime" if EMBEDDED
>> >> +	bool "Patch physical to virtual translations at runtime" if EMBEDDED || (ARCH_MULTIPLATFORM && MMU)
>> >>  	default y
>> >
>> > This makes no sense.  Multiplatform MMU _requires_ this feature, so why
>> > offer it to the user when multiplatform is enabled _and_ MMU is enabled?
>>
>> I see, this is plain wrong. Will replace that with a select ... if MMU
>> in multiplatform.
> 
> I think what I'd like to see is, in the top level choice:
> 
> config ARM_SINGLE_ARMV7M
> 	bool "ARM architecture v7M compliant (Cortex-M0/M3/M4) SoC"
> 	depends on !MMU
> 	select ARM_NVIC
> 	... etc ...

I guess that would be ARCH_SINGLE_ARMV7M?

> 
> which then allows a /multiplatform/ v7M kernel to be built, allowing the
> selection of EFM32, SOC_VF610, and any other v7M compliant SoC.

In my view, that wouldn't end up being much different than what that
patchset is doing:
With the introduction of ARCH_MULTI_V7M, we add something like a top
level v7M compliant selection. Due to the !MMU dependencies of all other
CPU families the family selection is minimal (when selecting !MMU):

    *** CPU Core family selection *** 
[*] ARMv7-M based platforms (Cortex-M)

And since ARCH_MULTI_V7M is not part of ARCH_MULTI_V6_V7 or anything,
the whole SoC selection contains only sensible SoC's without further
changes (also within the i.MX family, currently only "Vybrid Family
VF610 support" is selectable):

[ ] MMU-based Paged Memory Management Support                       
    ARM system type (Allow multiple platforms to be selected)  ---> 
    Multiple platform selection  --->                               
[*] Energy Micro efm32                                              
[*] Freescale i.MX family  --->    
    *** Processor Type ***
...

> So, it's very similar to multiplatform in the sense that several SoCs
> can be built together, but we preserve the need not to build
> incompatible stuff together.

As far as I can tell, this is already the case with that patchset.

The differences boil down to on which level we split the v7M CPU
selection apart: On ARCH_* level or ARCH_MULTI_* level. Given that we
allow a multiplatform _v7M kernel, the latter sounds more natural to
me...

Are there arguments to split v7M CPU selection apart on ARCH_* level
which I don't see?

--
Stefan

Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Russell King - ARM Linux]

On Mon, Apr 06, 2015 at 12:19:43AM +0200, Stefan Agner wrote:
> On 2015-04-05 18:10, Russell King - ARM Linux wrote:
> > config ARM_SINGLE_ARMV7M
> > 	bool "ARM architecture v7M compliant (Cortex-M0/M3/M4) SoC"
> > 	depends on !MMU
> > 	select ARM_NVIC
> > 	... etc ...
> 
> I guess that would be ARCH_SINGLE_ARMV7M?

No, I meant ARM_SINGLE_xxx

> > which then allows a /multiplatform/ v7M kernel to be built, allowing the
> > selection of EFM32, SOC_VF610, and any other v7M compliant SoC.
> 
> In my view, that wouldn't end up being much different than what that
> patchset is doing:

It's different.  It's different because we are _not_ enabling multiplatform.
Multiplatform brings with it all the MMU-full stuff that we don't want on
!MMU.

You're thinking far too specifically about V7M here.  We have other !MMU
CPUs, such as ARM946 and ARM940 which are older generation mmuless CPUs.

The problem with the ARCH_MULTI_V7M approach is that they're V4T and V5
CPUs, and we _really_ don't want to enable ARCH_MULTI_V4T and
ARCH_MULTI_V5.  If we did that, we'll allow _every_ V4T and V5
multiplatform to be selected, whether they're compatible with nommu
or not - and whether they're compatible with each other or not.

So, that kind of solution _doesn't_ scale to what we _once_ already
allowed.

> As far as I can tell, this is already the case with that patchset.

What I'm trying to do here is to fix the cockup that the multiplatform
conversion has created with previous generation noMMU and restore it
back to where it should be without excluding the newer stuff from it.

What you're interested in is just the newer stuff.  You're approaching
the problem from a different angle and thinking that your solution is
the best.  I'm saying it has deficiencies.

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Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Stefan Agner]

On 2015-04-06 00:44, Russell King - ARM Linux wrote:
> On Mon, Apr 06, 2015 at 12:19:43AM +0200, Stefan Agner wrote:
>> On 2015-04-05 18:10, Russell King - ARM Linux wrote:
>> > config ARM_SINGLE_ARMV7M
>> > 	bool "ARM architecture v7M compliant (Cortex-M0/M3/M4) SoC"
>> > 	depends on !MMU
>> > 	select ARM_NVIC
>> > 	... etc ...
>>
>> I guess that would be ARCH_SINGLE_ARMV7M?
> 
> No, I meant ARM_SINGLE_xxx
> 
>> > which then allows a /multiplatform/ v7M kernel to be built, allowing the
>> > selection of EFM32, SOC_VF610, and any other v7M compliant SoC.
>>
>> In my view, that wouldn't end up being much different than what that
>> patchset is doing:
> 
> It's different.  It's different because we are _not_ enabling multiplatform.
> Multiplatform brings with it all the MMU-full stuff that we don't want on
> !MMU.

You mean config symbols? There are 2-3 config symbols we don't want with
ARCH_MULTI_V7M and we have to exclude. But there would be also a
duplication of some already given by multiplatform when creating a new
top level config symbol...
 
> You're thinking far too specifically about V7M here.  We have other !MMU
> CPUs, such as ARM946 and ARM940 which are older generation mmuless CPUs.
> 
> The problem with the ARCH_MULTI_V7M approach is that they're V4T and V5
> CPUs, and we _really_ don't want to enable ARCH_MULTI_V4T and
> ARCH_MULTI_V5.  If we did that, we'll allow _every_ V4T and V5
> multiplatform to be selected, whether they're compatible with nommu
> or not - and whether they're compatible with each other or not.

Just from a selection view, ARM946 and ARM940 would still _not_ be
selectable because this change makes ARCH_MULTI_V4T/V5 being dependent
on MMU.

> 
> So, that kind of solution _doesn't_ scale to what we _once_ already
> allowed.
> 
>> As far as I can tell, this is already the case with that patchset.
> 
> What I'm trying to do here is to fix the cockup that the multiplatform
> conversion has created with previous generation noMMU and restore it
> back to where it should be without excluding the newer stuff from it.

Would be a partial revert (remove ARCH_MULTI_* from CPU_ARM940T and
CPU_ARM946E) of dc680b989d51 ("ARM: fix multiplatform allmodcompile") be
the right thing to do then? Given that ARCH_MULTI_V4T/V5 is MMU
dependent, those CPU's will not be selected even when building the
integrator multiplatform image... However, due to the selection
limitations outlined above, this would only be cosmetic anyway.
 
> What you're interested in is just the newer stuff.  You're approaching
> the problem from a different angle and thinking that your solution is
> the best.  I'm saying it has deficiencies.

When keeping the old CPU's out of multiplatform game properly, what
would speak against ARCH_MULTI_V7M? I still think if we allow a
multiplatform v7M image, it is cleaner to align that to the MMU
multiplatform stuff.

Maybe I don't really get the grasp of ARM_SINGLE_ARMV7M. In my
understanding it would be a new top level config symbol which kind of
merges ARCH_MULTIPLATFORM and ARCH_MULTI_V7M.

It is not my goal to enable !MMU on MULTIARCH per se. It's just that
when enabling V7M with ARCH_MULTIPLATFORM, it makes it easier to enable
the Cortex-M4 for the HMP platforms on those multiplatform only SoC's.
When creating a new config symbol on a high level, this advantage is
gone... I then could also create a top level ARCH_MXCV7M, which selects
multiplatform only ARCH_MXC.

--
Stefan

Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Russell King - ARM Linux]

On Mon, Apr 06, 2015 at 01:50:17AM +0200, Stefan Agner wrote:
> On 2015-04-06 00:44, Russell King - ARM Linux wrote:
> > On Mon, Apr 06, 2015 at 12:19:43AM +0200, Stefan Agner wrote:
> >> On 2015-04-05 18:10, Russell King - ARM Linux wrote:
> >> > config ARM_SINGLE_ARMV7M
> >> > 	bool "ARM architecture v7M compliant (Cortex-M0/M3/M4) SoC"
> >> > 	depends on !MMU
> >> > 	select ARM_NVIC
> >> > 	... etc ...
> >>
> >> I guess that would be ARCH_SINGLE_ARMV7M?
> > 
> > No, I meant ARM_SINGLE_xxx
> > 
> >> > which then allows a /multiplatform/ v7M kernel to be built, allowing the
> >> > selection of EFM32, SOC_VF610, and any other v7M compliant SoC.
> >>
> >> In my view, that wouldn't end up being much different than what that
> >> patchset is doing:
> > 
> > It's different.  It's different because we are _not_ enabling multiplatform.
> > Multiplatform brings with it all the MMU-full stuff that we don't want on
> > !MMU.
> 
> You mean config symbols? There are 2-3 config symbols we don't want with
> ARCH_MULTI_V7M and we have to exclude. But there would be also a
> duplication of some already given by multiplatform when creating a new
> top level config symbol...

Let me repeat: enabling multiplatform with !MMU is wrong.  It allows
you to build totally incompatible machines together that will never
boot.  It will cause users headaches when they try to build for something
only to find that they've got a bunch if incompatible other platforms
or other symbols enabled too.  Then they've got to work out how to
disable those, and that's not easy with the abuse that "select" gets.

> > You're thinking far too specifically about V7M here.  We have other !MMU
> > CPUs, such as ARM946 and ARM940 which are older generation mmuless CPUs.
> > 
> > The problem with the ARCH_MULTI_V7M approach is that they're V4T and V5
> > CPUs, and we _really_ don't want to enable ARCH_MULTI_V4T and
> > ARCH_MULTI_V5.  If we did that, we'll allow _every_ V4T and V5
> > multiplatform to be selected, whether they're compatible with nommu
> > or not - and whether they're compatible with each other or not.
> 
> Just from a selection view, ARM946 and ARM940 would still _not_ be
> selectable because this change makes ARCH_MULTI_V4T/V5 being dependent
> on MMU.

Thanks for telling me something I already know, and already have a patch
to fix.

> > So, that kind of solution _doesn't_ scale to what we _once_ already
> > allowed.
> > 
> >> As far as I can tell, this is already the case with that patchset.
> > 
> > What I'm trying to do here is to fix the cockup that the multiplatform
> > conversion has created with previous generation noMMU and restore it
> > back to where it should be without excluding the newer stuff from it.
> 
> Would be a partial revert (remove ARCH_MULTI_* from CPU_ARM940T and
> CPU_ARM946E) of dc680b989d51 ("ARM: fix multiplatform allmodcompile") be
> the right thing to do then? Given that ARCH_MULTI_V4T/V5 is MMU
> dependent, those CPU's will not be selected even when building the
> integrator multiplatform image... However, due to the selection
> limitations outlined above, this would only be cosmetic anyway.

You've identified the problem that I ran into... I already have this
fixed, thanks.

> > What you're interested in is just the newer stuff.  You're approaching
> > the problem from a different angle and thinking that your solution is
> > the best.  I'm saying it has deficiencies.
> 
> When keeping the old CPU's out of multiplatform game properly, what
> would speak against ARCH_MULTI_V7M? I still think if we allow a
> multiplatform v7M image, it is cleaner to align that to the MMU
> multiplatform stuff.
> 
> Maybe I don't really get the grasp of ARM_SINGLE_ARMV7M. In my
> understanding it would be a new top level config symbol which kind of
> merges ARCH_MULTIPLATFORM and ARCH_MULTI_V7M.

Exactly, but without the ability to select the other ARCH_MULTI_* symbols
along with ARCH_MULTI_V7M.

> It is not my goal to enable !MMU on MULTIARCH per se. It's just that
> when enabling V7M with ARCH_MULTIPLATFORM, it makes it easier to enable
> the Cortex-M4 for the HMP platforms on those multiplatform only SoC's.
> When creating a new config symbol on a high level, this advantage is
> gone... I then could also create a top level ARCH_MXCV7M, which selects
> multiplatform only ARCH_MXC.

No, you'd have a top level ARCH_SINGLE_ARMV7M.  You would then be
able to select the MXC V7M platforms along side any other V7M platform
because the V7M platforms share the same basic memory layout.

What you couldn't do is include _both_ support for Cortex-A9 and
Cortex-M4 in one image - the two are incompatible because they have
different physical address space layouts.

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Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Stefan Agner]

On 2015-04-06 10:15, Russell King - ARM Linux wrote:
> On Mon, Apr 06, 2015 at 01:50:17AM +0200, Stefan Agner wrote:
>> On 2015-04-06 00:44, Russell King - ARM Linux wrote:
>> > On Mon, Apr 06, 2015 at 12:19:43AM +0200, Stefan Agner wrote:
>> >> On 2015-04-05 18:10, Russell King - ARM Linux wrote:
>> >> > config ARM_SINGLE_ARMV7M
>> >> > 	bool "ARM architecture v7M compliant (Cortex-M0/M3/M4) SoC"
>> >> > 	depends on !MMU
>> >> > 	select ARM_NVIC
>> >> > 	... etc ...
>> >>
>> >> I guess that would be ARCH_SINGLE_ARMV7M?
>> >
>> > No, I meant ARM_SINGLE_xxx
>> >
>> >> > which then allows a /multiplatform/ v7M kernel to be built, allowing the
>> >> > selection of EFM32, SOC_VF610, and any other v7M compliant SoC.
>> >>
>> >> In my view, that wouldn't end up being much different than what that
>> >> patchset is doing:
>> >
>> > It's different.  It's different because we are _not_ enabling multiplatform.
>> > Multiplatform brings with it all the MMU-full stuff that we don't want on
>> > !MMU.
>>
>> You mean config symbols? There are 2-3 config symbols we don't want with
>> ARCH_MULTI_V7M and we have to exclude. But there would be also a
>> duplication of some already given by multiplatform when creating a new
>> top level config symbol...
> 
> Let me repeat: enabling multiplatform with !MMU is wrong.  It allows
> you to build totally incompatible machines together that will never
> boot.  It will cause users headaches when they try to build for something
> only to find that they've got a bunch if incompatible other platforms
> or other symbols enabled too.  Then they've got to work out how to
> disable those, and that's not easy with the abuse that "select" gets.
> 
>> > You're thinking far too specifically about V7M here.  We have other !MMU
>> > CPUs, such as ARM946 and ARM940 which are older generation mmuless CPUs.
>> >
>> > The problem with the ARCH_MULTI_V7M approach is that they're V4T and V5
>> > CPUs, and we _really_ don't want to enable ARCH_MULTI_V4T and
>> > ARCH_MULTI_V5.  If we did that, we'll allow _every_ V4T and V5
>> > multiplatform to be selected, whether they're compatible with nommu
>> > or not - and whether they're compatible with each other or not.
>>
>> Just from a selection view, ARM946 and ARM940 would still _not_ be
>> selectable because this change makes ARCH_MULTI_V4T/V5 being dependent
>> on MMU.
> 
> Thanks for telling me something I already know, and already have a patch
> to fix.
> 
>> > So, that kind of solution _doesn't_ scale to what we _once_ already
>> > allowed.
>> >
>> >> As far as I can tell, this is already the case with that patchset.
>> >
>> > What I'm trying to do here is to fix the cockup that the multiplatform
>> > conversion has created with previous generation noMMU and restore it
>> > back to where it should be without excluding the newer stuff from it.
>>
>> Would be a partial revert (remove ARCH_MULTI_* from CPU_ARM940T and
>> CPU_ARM946E) of dc680b989d51 ("ARM: fix multiplatform allmodcompile") be
>> the right thing to do then? Given that ARCH_MULTI_V4T/V5 is MMU
>> dependent, those CPU's will not be selected even when building the
>> integrator multiplatform image... However, due to the selection
>> limitations outlined above, this would only be cosmetic anyway.
> 
> You've identified the problem that I ran into... I already have this
> fixed, thanks.
> 
>> > What you're interested in is just the newer stuff.  You're approaching
>> > the problem from a different angle and thinking that your solution is
>> > the best.  I'm saying it has deficiencies.
>>
>> When keeping the old CPU's out of multiplatform game properly, what
>> would speak against ARCH_MULTI_V7M? I still think if we allow a
>> multiplatform v7M image, it is cleaner to align that to the MMU
>> multiplatform stuff.
>>
>> Maybe I don't really get the grasp of ARM_SINGLE_ARMV7M. In my
>> understanding it would be a new top level config symbol which kind of
>> merges ARCH_MULTIPLATFORM and ARCH_MULTI_V7M.
> 
> Exactly, but without the ability to select the other ARCH_MULTI_* symbols
> along with ARCH_MULTI_V7M.
> 
>> It is not my goal to enable !MMU on MULTIARCH per se. It's just that
>> when enabling V7M with ARCH_MULTIPLATFORM, it makes it easier to enable
>> the Cortex-M4 for the HMP platforms on those multiplatform only SoC's.
>> When creating a new config symbol on a high level, this advantage is
>> gone... I then could also create a top level ARCH_MXCV7M, which selects
>> multiplatform only ARCH_MXC.
> 
> No, you'd have a top level ARCH_SINGLE_ARMV7M.  You would then be
> able to select the MXC V7M platforms along side any other V7M platform
> because the V7M platforms share the same basic memory layout.
>
> What you couldn't do is include _both_ support for Cortex-A9 and
> Cortex-M4 in one image - the two are incompatible because they have
> different physical address space layouts.

We already prevent a kernel image which mixes V4/V4T/V5 and V6/V7. And
so we would do with V7M too. Just because it's in multiplatform doesn't
mean we need to mix things up.

--
Stefan

Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Russell King - ARM Linux]

On Mon, Apr 06, 2015 at 10:38:10AM +0200, Stefan Agner wrote:
> We already prevent a kernel image which mixes V4/V4T/V5 and V6/V7. And
> so we would do with V7M too. Just because it's in multiplatform doesn't
> mean we need to mix things up.

I don't think you're getting what I'm saying at all... :(

Please read the first bit of my replies again, where I say that we do
_not_ want to remove the !MMU dependency from multiplatform.  This is
something I feel _very_ strongly about, and something which I've written
about many times on this list.

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Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Stefan Agner]

On 2015-04-06 10:54, Russell King - ARM Linux wrote:
> On Mon, Apr 06, 2015 at 10:38:10AM +0200, Stefan Agner wrote:
>> We already prevent a kernel image which mixes V4/V4T/V5 and V6/V7. And
>> so we would do with V7M too. Just because it's in multiplatform doesn't
>> mean we need to mix things up.
> 
> I don't think you're getting what I'm saying at all... :(

It's not that I don't get it. I'm just arguing against it.

IMHO, it's wrong to create a parallel universe for v7M multiplatform...

Multiplatform as I understand it is mainly about selecting multiple SoC
_platforms_ but not necessarily multiple CPU platforms. It happens to
work well for V6/V7, but does not for others, and preventing
multiselection for incompatible CPU platforms is the way to prevent
creating such images.

> Please read the first bit of my replies again, where I say that we do
> _not_ want to remove the !MMU dependency from multiplatform.  This is
> something I feel _very_ strongly about, and something which I've written
> about many times on this list.

Ok, I don't have such a strong feel for multiplatform, it just feels a
bit better to me. I need a top level ARCH which is able to live with
!MMU. Will try the ARCH_SINGLE_ARMV7M approach then.

--
Stefan

Re: [PATCH v4 07/11] ARM: allow MULTIPLATFORM with !MMU

[Russell King - ARM Linux]

On Mon, Apr 06, 2015 at 11:33:53AM +0200, Stefan Agner wrote:
> On 2015-04-06 10:54, Russell King - ARM Linux wrote:
> > On Mon, Apr 06, 2015 at 10:38:10AM +0200, Stefan Agner wrote:
> >> We already prevent a kernel image which mixes V4/V4T/V5 and V6/V7. And
> >> so we would do with V7M too. Just because it's in multiplatform doesn't
> >> mean we need to mix things up.
> > 
> > I don't think you're getting what I'm saying at all... :(
> 
> It's not that I don't get it. I'm just arguing against it.
> 
> IMHO, it's wrong to create a parallel universe for v7M multiplatform...
> 
> Multiplatform as I understand it is mainly about selecting multiple SoC
> _platforms_ but not necessarily multiple CPU platforms. It happens to
> work well for V6/V7, but does not for others, and preventing
> multiselection for incompatible CPU platforms is the way to prevent
> creating such images.

Let's be clear: I'm _not_ arguing against being able to select multiple
SoC platforms at all.  I'm merely arguing about how it should be done.

What I'm saying, is that MULTIPLATFORM itself does _not_ work for all
noMMU platforms.  Yes, it _may_ work for V7M, but it doesn't work for
previous generation stuff - and that's confusing.

Let's look at what needs to happen to make V7M work the way you're
suggesting:
* Add "depends on !MMU" to all the existing ARCH_MULTI_* symbols.
* Append "if MMU" to the selection of ARM_PATCH_PHYS_VIRT and
  AUTO_ZRELADDR in multiplatform.

We then have the problem for the older generation noMMU stuff.  Should
we stuff into the multiplatform architecture options for selecting the
older generation noMMU _platforms_ into the "CPU Core family selection"
menu?  That's clearly wrong because they're not "CPU Cores".

So, we have to find somewhere else to put the older generation stuff,
and by doing so, that causes confusion, because we now have to select
multiplatform for one group of noMMU implementations, and _not_
select it for another group of noMMU implementations.

Imagine yourself writing up a document describing how to configure the
kernel for all noMMU platforms which will be read by many people with
varying degrees of English comprehension across the world, and how you
would describe to them, such that they clearly understood, how to
choose the right options.

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