MIPS: smp-cps: rework core/VPE initialisation

When hotplug and/or a powered down idle state are supported cases will
arise where a non-zero VPE must be brought online without VPE 0, and it
where multiple VPEs must be onlined simultaneously. This patch prepares
for that by:

  - Splitting struct boot_config into core & VPE boot config structures,
    allocated one per core or VPE respectively. This allows for multiple
    VPEs to be onlined simultaneously without clobbering each others
    configuration.

  - Indicating which VPEs should be online within a core at any given
    time using a bitmap. This allows multiple VPEs to be brought online
    simultaneously and also indicates to VPE 0 whether it should halt
    after starting any non-zero VPEs that should be online within the
    core. For example if all VPEs within a core are offlined via hotplug
    and the user onlines the second VPE within that core:

      1) The core will be powered up.

      2) VPE 0 will run from the BEV (ie. mips_cps_core_entry) to
         initialise the core.

      3) VPE 0 will start VPE 1 because its bit is set in the cores
         bitmap.

      4) VPE 0 will halt itself because its bit is clear in the cores
         bitmap.

  - Moving the core & VPE initialisation to assembly code which does not
    make any use of the stack. This is because if a non-zero VPE is to
    be brought online in a powered down core then when VPE 0 of that
    core runs it may not have a valid stack, and even if it did then
    it's messy to run through parts of generic kernel code on VPE 0
    before starting the correct VPE.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>

arch/mips/include/asm/smp-cps.h

@@ -13,17 +13,23 @@
 
 #ifndef __ASSEMBLY__
 
-struct boot_config {
-	unsigned int core;
-	unsigned int vpe;
+struct vpe_boot_config {
 	unsigned long pc;
 	unsigned long sp;
 	unsigned long gp;
 };
 
-extern struct boot_config mips_cps_bootcfg;
+struct core_boot_config {
+	atomic_t vpe_mask;
+	struct vpe_boot_config *vpe_config;
+};
+
+extern struct core_boot_config *mips_cps_core_bootcfg;
 
 extern void mips_cps_core_entry(void);
+extern void mips_cps_core_init(void);
+
+extern struct vpe_boot_config *mips_cps_boot_vpes(void);
 
 #else /* __ASSEMBLY__ */
 

arch/mips/kernel/asm-offsets.c

@@ -487,10 +487,14 @@ void output_kvm_defines(void)
 void output_cps_defines(void)
 {
 	COMMENT(" MIPS CPS offsets. ");
-	OFFSET(BOOTCFG_CORE, boot_config, core);
-	OFFSET(BOOTCFG_VPE, boot_config, vpe);
-	OFFSET(BOOTCFG_PC, boot_config, pc);
-	OFFSET(BOOTCFG_SP, boot_config, sp);
-	OFFSET(BOOTCFG_GP, boot_config, gp);
+
+	OFFSET(COREBOOTCFG_VPEMASK, core_boot_config, vpe_mask);
+	OFFSET(COREBOOTCFG_VPECONFIG, core_boot_config, vpe_config);
+	DEFINE(COREBOOTCFG_SIZE, sizeof(struct core_boot_config));
+
+	OFFSET(VPEBOOTCFG_PC, vpe_boot_config, pc);
+	OFFSET(VPEBOOTCFG_SP, vpe_boot_config, sp);
+	OFFSET(VPEBOOTCFG_GP, vpe_boot_config, gp);
+	DEFINE(VPEBOOTCFG_SIZE, sizeof(struct vpe_boot_config));
 }
 #endif

arch/mips/kernel/cps-vec.S

@@ -14,12 +14,33 @@
 #include <asm/asmmacro.h>
 #include <asm/cacheops.h>
 #include <asm/mipsregs.h>
+#include <asm/mipsmtregs.h>
 
-#define GCR_CL_COHERENCE_OFS 0x2008
+#define GCR_CL_COHERENCE_OFS	0x2008
+#define GCR_CL_ID_OFS		0x2028
+
+.extern mips_cm_base
+
+.set noreorder
+
+	/*
+	 * Set dest to non-zero if the core supports the MT ASE, else zero. If
+	 * MT is not supported then branch to nomt.
+	 */
+	.macro	has_mt	dest, nomt
+	mfc0	\dest, CP0_CONFIG
+	bgez	\dest, \nomt
+	 mfc0	\dest, CP0_CONFIG, 1
+	bgez	\dest, \nomt
+	 mfc0	\dest, CP0_CONFIG, 2
+	bgez	\dest, \nomt
+	 mfc0	\dest, CP0_CONFIG, 3
+	andi	\dest, \dest, MIPS_CONF3_MT
+	beqz	\dest, \nomt
+	.endm
 
 .section .text.cps-vec
 .balign 0x1000
-.set noreorder
 
 LEAF(mips_cps_core_entry)
 	/*
@@ -134,21 +155,24 @@ dcache_done:
 	jr	t0
 	 nop
 
-1:	/* We're up, cached & coherent */
+	/*
+	 * We're up, cached & coherent. Perform any further required core-level
+	 * initialisation.
+	 */
+1:	jal	mips_cps_core_init
+	 nop
 
 	/*
-	 * TODO: We should check the VPE number we intended to boot here, and
-	 *       if non-zero we should start that VPE and stop this one. For
-	 *       the moment this doesn't matter since CPUs are brought up
-	 *       sequentially and in order, but once hotplug is implemented
-	 *       this will need revisiting.
+	 * Boot any other VPEs within this core that should be online, and
+	 * deactivate this VPE if it should be offline.
 	 */
+	jal	mips_cps_boot_vpes
+	 nop
 
 	/* Off we go! */
-	la	t0, mips_cps_bootcfg
-	lw	t1, BOOTCFG_PC(t0)
-	lw	gp, BOOTCFG_GP(t0)
-	lw	sp, BOOTCFG_SP(t0)
+	lw	t1, VPEBOOTCFG_PC(v0)
+	lw	gp, VPEBOOTCFG_GP(v0)
+	lw	sp, VPEBOOTCFG_SP(v0)
 	jr	t1
 	 nop
 	END(mips_cps_core_entry)
@@ -189,3 +213,237 @@ LEAF(excep_ejtag)
 	jr	k0
 	 nop
 	END(excep_ejtag)
+
+LEAF(mips_cps_core_init)
+#ifdef CONFIG_MIPS_MT
+	/* Check that the core implements the MT ASE */
+	has_mt	t0, 3f
+	 nop
+
+	.set	push
+	.set	mt
+
+	/* Only allow 1 TC per VPE to execute... */
+	dmt
+
+	/* ...and for the moment only 1 VPE */
+	dvpe
+	la	t1, 1f
+	jr.hb	t1
+	 nop
+
+	/* Enter VPE configuration state */
+1:	mfc0	t0, CP0_MVPCONTROL
+	ori	t0, t0, MVPCONTROL_VPC
+	mtc0	t0, CP0_MVPCONTROL
+
+	/* Retrieve the number of VPEs within the core */
+	mfc0	t0, CP0_MVPCONF0
+	srl	t0, t0, MVPCONF0_PVPE_SHIFT
+	andi	t0, t0, (MVPCONF0_PVPE >> MVPCONF0_PVPE_SHIFT)
+	addi	t7, t0, 1
+
+	/* If there's only 1, we're done */
+	beqz	t0, 2f
+	 nop
+
+	/* Loop through each VPE within this core */
+	li	t5, 1
+
+1:	/* Operate on the appropriate TC */
+	mtc0	t5, CP0_VPECONTROL
+	ehb
+
+	/* Bind TC to VPE (1:1 TC:VPE mapping) */
+	mttc0	t5, CP0_TCBIND
+
+	/* Set exclusive TC, non-active, master */
+	li	t0, VPECONF0_MVP
+	sll	t1, t5, VPECONF0_XTC_SHIFT
+	or	t0, t0, t1
+	mttc0	t0, CP0_VPECONF0
+
+	/* Set TC non-active, non-allocatable */
+	mttc0	zero, CP0_TCSTATUS
+
+	/* Set TC halted */
+	li	t0, TCHALT_H
+	mttc0	t0, CP0_TCHALT
+
+	/* Next VPE */
+	addi	t5, t5, 1
+	slt	t0, t5, t7
+	bnez	t0, 1b
+	 nop
+
+	/* Leave VPE configuration state */
+2:	mfc0	t0, CP0_MVPCONTROL
+	xori	t0, t0, MVPCONTROL_VPC
+	mtc0	t0, CP0_MVPCONTROL
+
+3:	.set	pop
+#endif
+	jr	ra
+	 nop
+	END(mips_cps_core_init)
+
+LEAF(mips_cps_boot_vpes)
+	/* Retrieve CM base address */
+	la	t0, mips_cm_base
+	lw	t0, 0(t0)
+
+	/* Calculate a pointer to this cores struct core_boot_config */
+	lw	t0, GCR_CL_ID_OFS(t0)
+	li	t1, COREBOOTCFG_SIZE
+	mul	t0, t0, t1
+	la	t1, mips_cps_core_bootcfg
+	lw	t1, 0(t1)
+	addu	t0, t0, t1
+
+	/* Calculate this VPEs ID. If the core doesn't support MT use 0 */
+	has_mt	t6, 1f
+	 li	t9, 0
+
+	/* Find the number of VPEs present in the core */
+	mfc0	t1, CP0_MVPCONF0
+	srl	t1, t1, MVPCONF0_PVPE_SHIFT
+	andi	t1, t1, MVPCONF0_PVPE >> MVPCONF0_PVPE_SHIFT
+	addi	t1, t1, 1
+
+	/* Calculate a mask for the VPE ID from EBase.CPUNum */
+	clz	t1, t1
+	li	t2, 31
+	subu	t1, t2, t1
+	li	t2, 1
+	sll	t1, t2, t1
+	addiu	t1, t1, -1
+
+	/* Retrieve the VPE ID from EBase.CPUNum */
+	mfc0	t9, $15, 1
+	and	t9, t9, t1
+
+1:	/* Calculate a pointer to this VPEs struct vpe_boot_config */
+	li	t1, VPEBOOTCFG_SIZE
+	mul	v0, t9, t1
+	lw	t7, COREBOOTCFG_VPECONFIG(t0)
+	addu	v0, v0, t7
+
+#ifdef CONFIG_MIPS_MT
+
+	/* If the core doesn't support MT then return */
+	bnez	t6, 1f
+	 nop
+	jr	ra
+	 nop
+
+	.set	push
+	.set	mt
+
+1:	/* Enter VPE configuration state */
+	dvpe
+	la	t1, 1f
+	jr.hb	t1
+	 nop
+1:	mfc0	t1, CP0_MVPCONTROL
+	ori	t1, t1, MVPCONTROL_VPC
+	mtc0	t1, CP0_MVPCONTROL
+	ehb
+
+	/* Loop through each VPE */
+	lw	t6, COREBOOTCFG_VPEMASK(t0)
+	move	t8, t6
+	li	t5, 0
+
+	/* Check whether the VPE should be running. If not, skip it */
+1:	andi	t0, t6, 1
+	beqz	t0, 2f
+	 nop
+
+	/* Operate on the appropriate TC */
+	mfc0	t0, CP0_VPECONTROL
+	ori	t0, t0, VPECONTROL_TARGTC
+	xori	t0, t0, VPECONTROL_TARGTC
+	or	t0, t0, t5
+	mtc0	t0, CP0_VPECONTROL
+	ehb
+
+	/* Skip the VPE if its TC is not halted */
+	mftc0	t0, CP0_TCHALT
+	beqz	t0, 2f
+	 nop
+
+	/* Calculate a pointer to the VPEs struct vpe_boot_config */
+	li	t0, VPEBOOTCFG_SIZE
+	mul	t0, t0, t5
+	addu	t0, t0, t7
+
+	/* Set the TC restart PC */
+	lw	t1, VPEBOOTCFG_PC(t0)
+	mttc0	t1, CP0_TCRESTART
+
+	/* Set the TC stack pointer */
+	lw	t1, VPEBOOTCFG_SP(t0)
+	mttgpr	t1, sp
+
+	/* Set the TC global pointer */
+	lw	t1, VPEBOOTCFG_GP(t0)
+	mttgpr	t1, gp
+
+	/* Copy config from this VPE */
+	mfc0	t0, CP0_CONFIG
+	mttc0	t0, CP0_CONFIG
+
+	/* Ensure no software interrupts are pending */
+	mttc0	zero, CP0_CAUSE
+	mttc0	zero, CP0_STATUS
+
+	/* Set TC active, not interrupt exempt */
+	mftc0	t0, CP0_TCSTATUS
+	li	t1, ~TCSTATUS_IXMT
+	and	t0, t0, t1
+	ori	t0, t0, TCSTATUS_A
+	mttc0	t0, CP0_TCSTATUS
+
+	/* Clear the TC halt bit */
+	mttc0	zero, CP0_TCHALT
+
+	/* Set VPE active */
+	mftc0	t0, CP0_VPECONF0
+	ori	t0, t0, VPECONF0_VPA
+	mttc0	t0, CP0_VPECONF0
+
+	/* Next VPE */
+2:	srl	t6, t6, 1
+	addi	t5, t5, 1
+	bnez	t6, 1b
+	 nop
+
+	/* Leave VPE configuration state */
+	mfc0	t1, CP0_MVPCONTROL
+	xori	t1, t1, MVPCONTROL_VPC
+	mtc0	t1, CP0_MVPCONTROL
+	ehb
+	evpe
+
+	/* Check whether this VPE is meant to be running */
+	li	t0, 1
+	sll	t0, t0, t9
+	and	t0, t0, t8
+	bnez	t0, 2f
+	 nop
+
+	/* This VPE should be offline, halt the TC */
+	li	t0, TCHALT_H
+	mtc0	t0, CP0_TCHALT
+	la	t0, 1f
+1:	jr.hb	t0
+	 nop
+
+2:	.set	pop
+
+#endif /* CONFIG_MIPS_MT */
+
+	/* Return */
+	jr	ra
+	 nop
+	END(mips_cps_boot_vpes)

arch/mips/kernel/mips-cpc.c

@@ -9,6 +9,8 @@
  */
 
 #include <linux/errno.h>
+#include <linux/percpu.h>
+#include <linux/spinlock.h>
 
 #include <asm/mips-cm.h>
 #include <asm/mips-cpc.h>