Revert "ARM: OMAP4: remove dead kconfig option OMAP4_ERRATA_I688"

This reverts commit 606da482.

We actually need this code for proper behaviour of OMAP4, and it needs
fixing a different way other than just removing the code.  Disabling
code which is necessary in the hopes of persuing multiplatform kernels
is a stupid approach.
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Richard Woodruff <r-woodruff2@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-omap2/Kconfig

@@ -240,6 +240,27 @@ config OMAP3_SDRC_AC_TIMING
 	  wish to say no.  Selecting yes without understanding what is
 	  going on could result in system crashes;
 
+config OMAP4_ERRATA_I688
+	bool "OMAP4 errata: Async Bridge Corruption"
+	depends on (ARCH_OMAP4 || SOC_OMAP5) && !ARCH_MULTIPLATFORM
+	select ARCH_HAS_BARRIERS
+	help
+	  If a data is stalled inside asynchronous bridge because of back
+	  pressure, it may be accepted multiple times, creating pointer
+	  misalignment that will corrupt next transfers on that data path
+	  until next reset of the system (No recovery procedure once the
+	  issue is hit, the path remains consistently broken). Async bridge
+	  can be found on path between MPU to EMIF and MPU to L3 interconnect.
+	  This situation can happen only when the idle is initiated by a
+	  Master Request Disconnection (which is trigged by software when
+	  executing WFI on CPU).
+	  The work-around for this errata needs all the initiators connected
+	  through async bridge must ensure that data path is properly drained
+	  before issuing WFI. This condition will be met if one Strongly ordered
+	  access is performed to the target right before executing the WFI.
+	  In MPU case, L3 T2ASYNC FIFO and DDR T2ASYNC FIFO needs to be drained.
+	  IO barrier ensure that there is no synchronisation loss on initiators
+	  operating on both interconnect port simultaneously.
 endmenu
 
 endif

arch/arm/mach-omap2/common.c

@@ -30,4 +30,5 @@ int __weak omap_secure_ram_reserve_memblock(void)
 void __init omap_reserve(void)
 {
 	omap_secure_ram_reserve_memblock();
+	omap_barrier_reserve_memblock();
 }

arch/arm/mach-omap2/common.h

@@ -200,6 +200,9 @@ void __init omap4_map_io(void);
 void __init omap5_map_io(void);
 void __init ti81xx_map_io(void);
 
+/* omap_barriers_init() is OMAP4 only */
+void omap_barriers_init(void);
+
 /**
  * omap_test_timeout - busy-loop, testing a condition
  * @cond: condition to test until it evaluates to true

arch/arm/mach-omap2/io.c

@@ -306,6 +306,7 @@ void __init am33xx_map_io(void)
 void __init omap4_map_io(void)
 {
 	iotable_init(omap44xx_io_desc, ARRAY_SIZE(omap44xx_io_desc));
+	omap_barriers_init();
 }
 #endif
 
@@ -313,6 +314,7 @@ void __init omap4_map_io(void)
 void __init omap5_map_io(void)
 {
 	iotable_init(omap54xx_io_desc, ARRAY_SIZE(omap54xx_io_desc));
+	omap_barriers_init();
 }
 #endif
 /*

arch/arm/mach-omap2/omap-secure.h

@@ -70,6 +70,13 @@ extern u32 rx51_secure_dispatcher(u32 idx, u32 process, u32 flag, u32 nargs,
 extern u32 rx51_secure_update_aux_cr(u32 set_bits, u32 clear_bits);
 extern u32 rx51_secure_rng_call(u32 ptr, u32 count, u32 flag);
 
+#ifdef CONFIG_OMAP4_ERRATA_I688
+extern int omap_barrier_reserve_memblock(void);
+#else
+static inline void omap_barrier_reserve_memblock(void)
+{ }
+#endif
+
 #ifdef CONFIG_SOC_HAS_REALTIME_COUNTER
 void set_cntfreq(void);
 #else

arch/arm/mach-omap2/omap4-common.c

@@ -51,6 +51,75 @@ static void __iomem *twd_base;
 
 #define IRQ_LOCALTIMER		29
 
+#ifdef CONFIG_OMAP4_ERRATA_I688
+/* Used to implement memory barrier on DRAM path */
+#define OMAP4_DRAM_BARRIER_VA			0xfe600000
+
+void __iomem *dram_sync, *sram_sync;
+
+static phys_addr_t paddr;
+static u32 size;
+
+void omap_bus_sync(void)
+{
+	if (dram_sync && sram_sync) {
+		writel_relaxed(readl_relaxed(dram_sync), dram_sync);
+		writel_relaxed(readl_relaxed(sram_sync), sram_sync);
+		isb();
+	}
+}
+EXPORT_SYMBOL(omap_bus_sync);
+
+static int __init omap4_sram_init(void)
+{
+	struct device_node *np;
+	struct gen_pool *sram_pool;
+
+	np = of_find_compatible_node(NULL, NULL, "ti,omap4-mpu");
+	if (!np)
+		pr_warn("%s:Unable to allocate sram needed to handle errata I688\n",
+			__func__);
+	sram_pool = of_get_named_gen_pool(np, "sram", 0);
+	if (!sram_pool)
+		pr_warn("%s:Unable to get sram pool needed to handle errata I688\n",
+			__func__);
+	else
+		sram_sync = (void *)gen_pool_alloc(sram_pool, PAGE_SIZE);
+
+	return 0;
+}
+omap_arch_initcall(omap4_sram_init);
+
+/* Steal one page physical memory for barrier implementation */
+int __init omap_barrier_reserve_memblock(void)
+{
+
+	size = ALIGN(PAGE_SIZE, SZ_1M);
+	paddr = arm_memblock_steal(size, SZ_1M);
+
+	return 0;
+}
+
+void __init omap_barriers_init(void)
+{
+	struct map_desc dram_io_desc[1];
+
+	dram_io_desc[0].virtual = OMAP4_DRAM_BARRIER_VA;
+	dram_io_desc[0].pfn = __phys_to_pfn(paddr);
+	dram_io_desc[0].length = size;
+	dram_io_desc[0].type = MT_MEMORY_RW_SO;
+	iotable_init(dram_io_desc, ARRAY_SIZE(dram_io_desc));
+	dram_sync = (void __iomem *) dram_io_desc[0].virtual;
+
+	pr_info("OMAP4: Map 0x%08llx to 0x%08lx for dram barrier\n",
+		(long long) paddr, dram_io_desc[0].virtual);
+
+}
+#else
+void __init omap_barriers_init(void)
+{}
+#endif
+
 void gic_dist_disable(void)
 {
 	if (gic_dist_base_addr)

arch/arm/mach-omap2/sleep44xx.S

@@ -333,9 +333,11 @@ ENDPROC(omap4_cpu_resume)
 
 #endif	/* defined(CONFIG_SMP) && defined(CONFIG_PM) */
 
+#ifndef CONFIG_OMAP4_ERRATA_I688
 ENTRY(omap_bus_sync)
 	ret	lr
 ENDPROC(omap_bus_sync)
+#endif
 
 ENTRY(omap_do_wfi)
 	stmfd	sp!, {lr}