ARM: Delete ARM11MPCore (ARM11 ARMv6K SMP) support

This ARM11 SMP configuration was one of the first SMP configurations
the ARM kernel supported, but it has the downside of odd DMA handling,
odd cache tagging, and often (as of recent) completely broken cache
handling on the ARM RealView PB11MPCore test chips. To boot the
platform it was necessary to completely disable the cache.
When it comes to the EB 11MPCore it is unclear if this ever worked.

These reference designs are now the only ARMv6K SMP platforms.

As only reference designs of purely academic interest remain, and
since the special-cased DMA and PMU code is hard to maintain and
doesn't really work, it is not really worth our time.

Delete the ARM11MPCore support along with:

- The special DMA quirk CONFIG_DMA_CACHE_RWFO that is only used
  on ARMv6K SMP, and we are the last ARMV6K system leaving the
  building and the cache handling is awkward, so good-bye.

- The special PMU handling that was only used by ARM11MPCore.

The following is left behind:

- TIMER_OF_DECLARE(arm_twd_11mp, "arm,arm11mp-twd-timer", ...)
  in arch/arm/kernel/smp_twd.c, this is still in use by Marvell MMP3
  arch/arm/boot/dts/marvell/mmp3.dtsi

- IRQCHIP_DECLARE(arm11mp_gic, "arm,arm11mp-gic", ...)
  in drivers/irqchip/irq-gic.c, this is still in use by Marvell MMP3
  arch/arm/boot/dts/marvell/mmp3.dtsi

- A compatible for the arm11mpcore SCU, since this was mistakedly
  used for the Cortex-A9 version of RealView EB.

These are unfortunate but will need to be kept around for
compatibility. New Marvell-specific compatibles should however probably
be added.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://lore.kernel.org/r/20231207-drop-11mpcore-v2-1-560b396f3bf5@linaro.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Author: Linus Walleij

arch/arm/kernel/perf_event_v6.c

@@ -525,40 +525,7 @@ static int armv6_1176_pmu_init(struct arm_pmu *cpu_pmu)
 	return 0;
 }
 
-/*
- * ARMv6mpcore is almost identical to single core ARMv6 with the exception
- * that some of the events have different enumerations and that there is no
- * *hack* to stop the programmable counters. To stop the counters we simply
- * disable the interrupt reporting and update the event. When unthrottling we
- * reset the period and enable the interrupt reporting.
- */
-
-static int armv6mpcore_map_event(struct perf_event *event)
-{
-	return armpmu_map_event(event, &armv6mpcore_perf_map,
-				&armv6mpcore_perf_cache_map, 0xFF);
-}
-
-static int armv6mpcore_pmu_init(struct arm_pmu *cpu_pmu)
-{
-	cpu_pmu->name		= "armv6_11mpcore";
-	cpu_pmu->handle_irq	= armv6pmu_handle_irq;
-	cpu_pmu->enable		= armv6pmu_enable_event;
-	cpu_pmu->disable	= armv6mpcore_pmu_disable_event;
-	cpu_pmu->read_counter	= armv6pmu_read_counter;
-	cpu_pmu->write_counter	= armv6pmu_write_counter;
-	cpu_pmu->get_event_idx	= armv6pmu_get_event_idx;
-	cpu_pmu->clear_event_idx = armv6pmu_clear_event_idx;
-	cpu_pmu->start		= armv6pmu_start;
-	cpu_pmu->stop		= armv6pmu_stop;
-	cpu_pmu->map_event	= armv6mpcore_map_event;
-	cpu_pmu->num_events	= 3;
-
-	return 0;
-}
-
 static const struct of_device_id armv6_pmu_of_device_ids[] = {
-	{.compatible = "arm,arm11mpcore-pmu",	.data = armv6mpcore_pmu_init},
 	{.compatible = "arm,arm1176-pmu",	.data = armv6_1176_pmu_init},
 	{.compatible = "arm,arm1136-pmu",	.data = armv6_1136_pmu_init},
 	{ /* sentinel value */ }
@@ -568,7 +535,6 @@ static const struct pmu_probe_info armv6_pmu_probe_table[] = {
 	ARM_PMU_PROBE(ARM_CPU_PART_ARM1136, armv6_1136_pmu_init),
 	ARM_PMU_PROBE(ARM_CPU_PART_ARM1156, armv6_1156_pmu_init),
 	ARM_PMU_PROBE(ARM_CPU_PART_ARM1176, armv6_1176_pmu_init),
-	ARM_PMU_PROBE(ARM_CPU_PART_ARM11MPCORE, armv6mpcore_pmu_init),
 	{ /* sentinel value */ }
 };
 

arch/arm/mach-versatile/Kconfig

@@ -201,23 +201,6 @@ config REALVIEW_EB_A9MP
 	  Enable support for the Cortex-A9MPCore tile fitted to the
 	  Realview(R) Emulation Baseboard platform.
 
-config REALVIEW_EB_ARM11MP
-	bool "Support ARM11MPCore Tile"
-	depends on MACH_REALVIEW_EB && ARCH_MULTI_V6
-	select HAVE_SMP
-	help
-	  Enable support for the ARM11MPCore tile fitted to the Realview(R)
-	  Emulation Baseboard platform.
-
-config MACH_REALVIEW_PB11MP
-	bool "Support RealView(R) Platform Baseboard for ARM11MPCore"
-	depends on ARCH_MULTI_V6
-	select HAVE_SMP
-	help
-	  Include support for the ARM(R) RealView(R) Platform Baseboard for
-	  the ARM11MPCore.  This platform has an on-board ARM11MPCore and has
-	  support for PCI-E and Compact Flash.
-
 # ARMv6 CPU without K extensions, but does have the new exclusive ops
 config MACH_REALVIEW_PB1176
 	bool "Support RealView(R) Platform Baseboard for ARM1176JZF-S"

arch/arm/mach-versatile/platsmp-realview.c

@@ -18,6 +18,11 @@
 #define REALVIEW_SYS_FLAGSSET_OFFSET	0x30
 
 static const struct of_device_id realview_scu_match[] = {
+	/*
+	 * The ARM11MP SCU compatible is only provided as fallback for
+	 * old RealView EB Cortex-A9 device trees that were using this
+	 * compatible by mistake.
+	 */
 	{ .compatible = "arm,arm11mp-scu", },
 	{ .compatible = "arm,cortex-a9-scu", },
 	{ .compatible = "arm,cortex-a5-scu", },
@@ -27,7 +32,6 @@ static const struct of_device_id realview_scu_match[] = {
 static const struct of_device_id realview_syscon_match[] = {
         { .compatible = "arm,core-module-integrator", },
         { .compatible = "arm,realview-eb-syscon", },
-        { .compatible = "arm,realview-pb11mp-syscon", },
         { .compatible = "arm,realview-pbx-syscon", },
         { },
 };

arch/arm/mach-versatile/realview.c

@@ -9,7 +9,6 @@
 static const char *const realview_dt_platform_compat[] __initconst = {
 	"arm,realview-eb",
 	"arm,realview-pb1176",
-	"arm,realview-pb11mp",
 	"arm,realview-pba8",
 	"arm,realview-pbx",
 	NULL,

arch/arm/mm/Kconfig

@@ -937,24 +937,6 @@ config VDSO
 	  You must have glibc 2.22 or later for programs to seamlessly
 	  take advantage of this.
 
-config DMA_CACHE_RWFO
-	bool "Enable read/write for ownership DMA cache maintenance"
-	depends on CPU_V6K && SMP
-	default y
-	help
-	  The Snoop Control Unit on ARM11MPCore does not detect the
-	  cache maintenance operations and the dma_{map,unmap}_area()
-	  functions may leave stale cache entries on other CPUs. By
-	  enabling this option, Read or Write For Ownership in the ARMv6
-	  DMA cache maintenance functions is performed. These LDR/STR
-	  instructions change the cache line state to shared or modified
-	  so that the cache operation has the desired effect.
-
-	  Note that the workaround is only valid on processors that do
-	  not perform speculative loads into the D-cache. For such
-	  processors, if cache maintenance operations are not broadcast
-	  in hardware, other workarounds are needed (e.g. cache
-	  maintenance broadcasting in software via FIQ).
 
 config OUTER_CACHE
 	bool

arch/arm/mm/cache-v6.S

@@ -201,10 +201,6 @@ ENTRY(v6_flush_kern_dcache_area)
  *	- end     - virtual end address of region
  */
 v6_dma_inv_range:
-#ifdef CONFIG_DMA_CACHE_RWFO
-	ldrb	r2, [r0]			@ read for ownership
-	strb	r2, [r0]			@ write for ownership
-#endif
 	tst	r0, #D_CACHE_LINE_SIZE - 1
 	bic	r0, r0, #D_CACHE_LINE_SIZE - 1
 #ifdef HARVARD_CACHE
@@ -213,10 +209,6 @@ v6_dma_inv_range:
 	mcrne	p15, 0, r0, c7, c11, 1		@ clean unified line
 #endif
 	tst	r1, #D_CACHE_LINE_SIZE - 1
-#ifdef CONFIG_DMA_CACHE_RWFO
-	ldrbne	r2, [r1, #-1]			@ read for ownership
-	strbne	r2, [r1, #-1]			@ write for ownership
-#endif
 	bic	r1, r1, #D_CACHE_LINE_SIZE - 1
 #ifdef HARVARD_CACHE
 	mcrne	p15, 0, r1, c7, c14, 1		@ clean & invalidate D line
@@ -231,10 +223,6 @@ v6_dma_inv_range:
 #endif
 	add	r0, r0, #D_CACHE_LINE_SIZE
 	cmp	r0, r1
-#ifdef CONFIG_DMA_CACHE_RWFO
-	ldrlo	r2, [r0]			@ read for ownership
-	strlo	r2, [r0]			@ write for ownership
-#endif
 	blo	1b
 	mov	r0, #0
 	mcr	p15, 0, r0, c7, c10, 4		@ drain write buffer
@@ -248,9 +236,6 @@ v6_dma_inv_range:
 v6_dma_clean_range:
 	bic	r0, r0, #D_CACHE_LINE_SIZE - 1
 1:
-#ifdef CONFIG_DMA_CACHE_RWFO
-	ldr	r2, [r0]			@ read for ownership
-#endif
 #ifdef HARVARD_CACHE
 	mcr	p15, 0, r0, c7, c10, 1		@ clean D line
 #else
@@ -269,10 +254,6 @@ v6_dma_clean_range:
  *	- end     - virtual end address of region
  */
 ENTRY(v6_dma_flush_range)
-#ifdef CONFIG_DMA_CACHE_RWFO
-	ldrb	r2, [r0]		@ read for ownership
-	strb	r2, [r0]		@ write for ownership
-#endif
 	bic	r0, r0, #D_CACHE_LINE_SIZE - 1
 1:
 #ifdef HARVARD_CACHE
@@ -282,10 +263,6 @@ ENTRY(v6_dma_flush_range)
 #endif
 	add	r0, r0, #D_CACHE_LINE_SIZE
 	cmp	r0, r1
-#ifdef CONFIG_DMA_CACHE_RWFO
-	ldrblo	r2, [r0]			@ read for ownership
-	strblo	r2, [r0]			@ write for ownership
-#endif
 	blo	1b
 	mov	r0, #0
 	mcr	p15, 0, r0, c7, c10, 4		@ drain write buffer
@@ -301,13 +278,7 @@ ENTRY(v6_dma_map_area)
 	add	r1, r1, r0
 	teq	r2, #DMA_FROM_DEVICE
 	beq	v6_dma_inv_range
-#ifndef CONFIG_DMA_CACHE_RWFO
 	b	v6_dma_clean_range
-#else
-	teq	r2, #DMA_TO_DEVICE
-	beq	v6_dma_clean_range
-	b	v6_dma_flush_range
-#endif
 ENDPROC(v6_dma_map_area)
 
 /*
@@ -317,11 +288,9 @@ ENDPROC(v6_dma_map_area)
  *	- dir	- DMA direction
  */
 ENTRY(v6_dma_unmap_area)
-#ifndef CONFIG_DMA_CACHE_RWFO
 	add	r1, r1, r0
 	teq	r2, #DMA_TO_DEVICE
 	bne	v6_dma_inv_range
-#endif
 	ret	lr
 ENDPROC(v6_dma_unmap_area)