Re: [PATCH] Retain the write-only OD from being clobbered

[Sergei Shtylyov <sshtylyov@dev.rtsoft.ru>]

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Hello.

     Retain the write-only OD bit from being clobbered by coherency_setup().

WBR, Sergei

PS: Looks like this patch is stuck uncommitted since December, while it's a
serious issue causing the kernel lockups.

Signed-off-by: Konstantin Baidarov <kbaidarov@ru.mvista.com>
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>



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diff --git a/arch/mips/au1000/common/setup.c b/arch/mips/au1000/common/setup.c
index 08c8c85..e36289b 100644
--- a/arch/mips/au1000/common/setup.c
+++ b/arch/mips/au1000/common/setup.c
@@ -143,6 +143,17 @@ void __init plat_setup(void)
 	au_writel(0, SYS_TOYTRIM);
 }
 
+/*
+ * Fix up write-only Config[OD] bit after a write to that register. Since the
+ * bit always reads as 0 on those SOC revs that require it to be set to fight
+ * the various errata, we need to set it back to 1...
+ */
+void au1x00_fixup_config_od(void)
+{
+	if (cur_cpu_spec[0]->cpu_od)
+		set_c0_config(1<<19);
+}
+
 #if defined(CONFIG_64BIT_PHYS_ADDR)
 /* This routine should be valid for all Au1x based boards */
 phys_t __fixup_bigphys_addr(phys_t phys_addr, phys_t size)
diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
index 422b55f..8447699 100644
--- a/arch/mips/mm/c-r4k.c
+++ b/arch/mips/mm/c-r4k.c
@@ -1201,8 +1201,20 @@ static void __init setup_scache(void)
 
 static inline void coherency_setup(void)
 {
+	extern void au1x00_fixup_config_od(void);
+
 	change_c0_config(CONF_CM_CMASK, CONF_CM_DEFAULT);
 
+#ifdef CONFIG_SOC_AU1X00
+	/*
+	 * c0_config.od (bit 19) is write only (and reads as 0) on many early
+	 * revs of AMD Au1x00 SOCs. It disables the bus transaction overlapping
+	 * and needs to be set to correct the various errata. So if it has been
+	 * set by the board setup code we must leave it set...
+	 */
+	au1x00_fixup_config_od();
+#endif
+
 	/*
 	 * c0_status.cu=0 specifies that updates by the sc instruction use
 	 * the coherency mode specified by the TLB; 1 means cachable