ARCv2: SLC: Allow boot time disable

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/mm/cache.c

@@ -23,6 +23,7 @@
 
 static int l2_line_sz;
 int ioc_exists;
+volatile int slc_enable = 1;
 
 void (*_cache_line_loop_ic_fn)(unsigned long paddr, unsigned long vaddr,
 			       unsigned long sz, const int cacheop);
@@ -36,6 +37,7 @@ char *arc_cache_mumbojumbo(int c, char *buf, int len)
 	int n = 0;
 	struct cpuinfo_arc_cache *p;
 
+#define IS_USED_RUN(v)		((v) ? "" : "(disabled) ")
 #define PR_CACHE(p, cfg, str)						\
 	if (!(p)->ver)							\
 		n += scnprintf(buf + n, len - n, str"\t\t: N/A\n");	\
@@ -53,7 +55,8 @@ char *arc_cache_mumbojumbo(int c, char *buf, int len)
 	p = &cpuinfo_arc700[c].slc;
 	if (p->ver)
 		n += scnprintf(buf + n, len - n,
-			"SLC\t\t: %uK, %uB Line\n", p->sz_k, p->line_len);
+			       "SLC\t\t: %uK, %uB Line%s\n",
+			       p->sz_k, p->line_len, IS_USED_RUN(slc_enable));
 
 	if (ioc_exists)
 		n += scnprintf(buf + n, len - n, "IOC\t\t: exists\n");
@@ -908,6 +911,20 @@ void arc_cache_init(void)
 		}
 	}
 
+	if (is_isa_arcv2() && l2_line_sz && !slc_enable) {
+
+		/* IM set : flush before invalidate */
+		write_aux_reg(ARC_REG_SLC_CTRL,
+			read_aux_reg(ARC_REG_SLC_CTRL) | SLC_CTRL_IM);
+
+		write_aux_reg(ARC_REG_SLC_INVALIDATE, 1);
+
+		/* Important to wait for flush to complete */
+		while (read_aux_reg(ARC_REG_SLC_CTRL) & SLC_CTRL_BUSY);
+		write_aux_reg(ARC_REG_SLC_CTRL,
+			read_aux_reg(ARC_REG_SLC_CTRL) | SLC_CTRL_DISABLE);
+	}
+
 	if (is_isa_arcv2() && ioc_exists) {
 		/* IO coherency base - 0x8z */
 		write_aux_reg(ARC_REG_IO_COH_AP0_BASE, 0x80000);
@@ -921,7 +938,7 @@ void arc_cache_init(void)
 		__dma_cache_wback_inv = __dma_cache_wback_inv_ioc;
 		__dma_cache_inv = __dma_cache_inv_ioc;
 		__dma_cache_wback = __dma_cache_wback_ioc;
-	} else if (is_isa_arcv2() && l2_line_sz) {
+	} else if (is_isa_arcv2() && l2_line_sz && slc_enable) {
 		__dma_cache_wback_inv = __dma_cache_wback_inv_slc;
 		__dma_cache_inv = __dma_cache_inv_slc;
 		__dma_cache_wback = __dma_cache_wback_slc;