MIPS: Enable L2 prefetching for CM >= 2.5

On systems with CM 2.5 & beyond there may be L2 prefetch units present
which are not enabled by default. Detect them, configuring & enabling
prefetching when available.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: linux-kernel@vger.kernel.org
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/11180/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/mips-cm.h

@@ -195,6 +195,8 @@ BUILD_CM_R_(gic_status,		MIPS_CM_GCB_OFS + 0xd0)
 BUILD_CM_R_(cpc_status,		MIPS_CM_GCB_OFS + 0xf0)
 BUILD_CM_RW(l2_config,		MIPS_CM_GCB_OFS + 0x130)
 BUILD_CM_RW(sys_config2,	MIPS_CM_GCB_OFS + 0x150)
+BUILD_CM_RW(l2_pft_control,	MIPS_CM_GCB_OFS + 0x300)
+BUILD_CM_RW(l2_pft_control_b,	MIPS_CM_GCB_OFS + 0x308)
 
 /* Core Local & Core Other register accessor functions */
 BUILD_CM_Cx_RW(reset_release,	0x00)
@@ -245,6 +247,7 @@ BUILD_CM_Cx_R_(tcid_8_priority,	0x80)
 		 ((minor) << CM_GCR_REV_MINOR_SHF))
 
 #define CM_REV_CM2				CM_ENCODE_REV(6, 0)
+#define CM_REV_CM2_5				CM_ENCODE_REV(7, 0)
 #define CM_REV_CM3				CM_ENCODE_REV(8, 0)
 
 /* GCR_ERROR_CAUSE register fields */
@@ -321,6 +324,20 @@ BUILD_CM_Cx_R_(tcid_8_priority,	0x80)
 #define CM_GCR_SYS_CONFIG2_MAXVPW_SHF		0
 #define CM_GCR_SYS_CONFIG2_MAXVPW_MSK		(_ULCAST_(0xf) << 0)
 
+/* GCR_L2_PFT_CONTROL register fields */
+#define CM_GCR_L2_PFT_CONTROL_PAGEMASK_SHF	12
+#define CM_GCR_L2_PFT_CONTROL_PAGEMASK_MSK	(_ULCAST_(0xfffff) << 12)
+#define CM_GCR_L2_PFT_CONTROL_PFTEN_SHF		8
+#define CM_GCR_L2_PFT_CONTROL_PFTEN_MSK		(_ULCAST_(0x1) << 8)
+#define CM_GCR_L2_PFT_CONTROL_NPFT_SHF		0
+#define CM_GCR_L2_PFT_CONTROL_NPFT_MSK		(_ULCAST_(0xff) << 0)
+
+/* GCR_L2_PFT_CONTROL_B register fields */
+#define CM_GCR_L2_PFT_CONTROL_B_CEN_SHF		8
+#define CM_GCR_L2_PFT_CONTROL_B_CEN_MSK		(_ULCAST_(0x1) << 8)
+#define CM_GCR_L2_PFT_CONTROL_B_PORTID_SHF	0
+#define CM_GCR_L2_PFT_CONTROL_B_PORTID_MSK	(_ULCAST_(0xff) << 0)
+
 /* GCR_Cx_COHERENCE register fields */
 #define CM_GCR_Cx_COHERENCE_COHDOMAINEN_SHF	0
 #define CM_GCR_Cx_COHERENCE_COHDOMAINEN_MSK	(_ULCAST_(0xff) << 0)

arch/mips/mm/sc-mips.c

@@ -51,11 +51,69 @@ static void mips_sc_disable(void)
 	/* L2 cache is permanently enabled */
 }
 
+static void mips_sc_prefetch_enable(void)
+{
+	unsigned long pftctl;
+
+	if (mips_cm_revision() < CM_REV_CM2_5)
+		return;
+
+	/*
+	 * If there is one or more L2 prefetch unit present then enable
+	 * prefetching for both code & data, for all ports.
+	 */
+	pftctl = read_gcr_l2_pft_control();
+	if (pftctl & CM_GCR_L2_PFT_CONTROL_NPFT_MSK) {
+		pftctl &= ~CM_GCR_L2_PFT_CONTROL_PAGEMASK_MSK;
+		pftctl |= PAGE_MASK & CM_GCR_L2_PFT_CONTROL_PAGEMASK_MSK;
+		pftctl |= CM_GCR_L2_PFT_CONTROL_PFTEN_MSK;
+		write_gcr_l2_pft_control(pftctl);
+
+		pftctl = read_gcr_l2_pft_control_b();
+		pftctl |= CM_GCR_L2_PFT_CONTROL_B_PORTID_MSK;
+		pftctl |= CM_GCR_L2_PFT_CONTROL_B_CEN_MSK;
+		write_gcr_l2_pft_control_b(pftctl);
+	}
+}
+
+static void mips_sc_prefetch_disable(void)
+{
+	unsigned long pftctl;
+
+	if (mips_cm_revision() < CM_REV_CM2_5)
+		return;
+
+	pftctl = read_gcr_l2_pft_control();
+	pftctl &= ~CM_GCR_L2_PFT_CONTROL_PFTEN_MSK;
+	write_gcr_l2_pft_control(pftctl);
+
+	pftctl = read_gcr_l2_pft_control_b();
+	pftctl &= ~CM_GCR_L2_PFT_CONTROL_B_PORTID_MSK;
+	pftctl &= ~CM_GCR_L2_PFT_CONTROL_B_CEN_MSK;
+	write_gcr_l2_pft_control_b(pftctl);
+}
+
+static bool mips_sc_prefetch_is_enabled(void)
+{
+	unsigned long pftctl;
+
+	if (mips_cm_revision() < CM_REV_CM2_5)
+		return false;
+
+	pftctl = read_gcr_l2_pft_control();
+	if (!(pftctl & CM_GCR_L2_PFT_CONTROL_NPFT_MSK))
+		return false;
+	return !!(pftctl & CM_GCR_L2_PFT_CONTROL_PFTEN_MSK);
+}
+
 static struct bcache_ops mips_sc_ops = {
 	.bc_enable = mips_sc_enable,
 	.bc_disable = mips_sc_disable,
 	.bc_wback_inv = mips_sc_wback_inv,
-	.bc_inv = mips_sc_inv
+	.bc_inv = mips_sc_inv,
+	.bc_prefetch_enable = mips_sc_prefetch_enable,
+	.bc_prefetch_disable = mips_sc_prefetch_disable,
+	.bc_prefetch_is_enabled = mips_sc_prefetch_is_enabled,
 };
 
 /*
@@ -186,6 +244,7 @@ int mips_sc_init(void)
 	int found = mips_sc_probe();
 	if (found) {
 		mips_sc_enable();
+		mips_sc_prefetch_enable();
 		bcops = &mips_sc_ops;
 	}
 	return found;