[PATCH v3 6/8] powerpc/xive: introduce H_INT_ESB hcall

["Cédric Le Goater" <clg@kaod.org>]

The H_INT_ESB hcall() is used to issue a load or store to the ESB page
instead of using the MMIO pages. This can be used as a workaround on
some HW issues. The OS knows that this hcall should be used on an
interrupt source when the ESB hcall flag is set to 1 in the hcall
H_INT_GET_SOURCE_INFO.

To maintain the frontier between the xive frontend and backend, we
introduce a new xive operation 'esb_rw' to be used in the routines
doing memory accesses on the ESBs.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
---
 arch/powerpc/include/asm/xive.h          |  1 +
 arch/powerpc/sysdev/xive/common.c        | 10 ++++++--
 arch/powerpc/sysdev/xive/spapr.c         | 44 +++++++++++++++++++++++++++++++-
 arch/powerpc/sysdev/xive/xive-internal.h |  1 +
 4 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/xive.h b/arch/powerpc/include/asm/xive.h
index 64ec9bbcf03e..371fbebf1ec9 100644
--- a/arch/powerpc/include/asm/xive.h
+++ b/arch/powerpc/include/asm/xive.h
@@ -56,6 +56,7 @@ struct xive_irq_data {
 #define XIVE_IRQ_FLAG_SHIFT_BUG	0x04
 #define XIVE_IRQ_FLAG_MASK_FW	0x08
 #define XIVE_IRQ_FLAG_EOI_FW	0x10
+#define XIVE_IRQ_FLAG_H_INT_ESB	0x20
 
 #define XIVE_INVALID_CHIP_ID	-1
 
diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c
index ac5f18a66742..8fd58773c241 100644
--- a/arch/powerpc/sysdev/xive/common.c
+++ b/arch/powerpc/sysdev/xive/common.c
@@ -198,7 +198,10 @@ static u8 xive_esb_read(struct xive_irq_data *xd, u32 offset)
 	if (xd->flags & XIVE_IRQ_FLAG_SHIFT_BUG)
 		offset |= offset << 4;
 
-	val = in_be64(xd->eoi_mmio + offset);
+	if ((xd->flags & XIVE_IRQ_FLAG_H_INT_ESB) && xive_ops->esb_rw)
+		val = xive_ops->esb_rw(xd->hw_irq, offset, 0, 0);
+	else
+		val = in_be64(xd->eoi_mmio + offset);
 
 	return (u8)val;
 }
@@ -209,7 +212,10 @@ static void xive_esb_write(struct xive_irq_data *xd, u32 offset, u64 data)
 	if (xd->flags & XIVE_IRQ_FLAG_SHIFT_BUG)
 		offset |= offset << 4;
 
-	out_be64(xd->eoi_mmio + offset, data);
+	if ((xd->flags & XIVE_IRQ_FLAG_H_INT_ESB) && xive_ops->esb_rw)
+		xive_ops->esb_rw(xd->hw_irq, offset, data, 1);
+	else
+		out_be64(xd->eoi_mmio + offset, data);
 }
 
 #ifdef CONFIG_XMON
diff --git a/arch/powerpc/sysdev/xive/spapr.c b/arch/powerpc/sysdev/xive/spapr.c
index 0fcae7504353..43e9eeb0d39f 100644
--- a/arch/powerpc/sysdev/xive/spapr.c
+++ b/arch/powerpc/sysdev/xive/spapr.c
@@ -224,7 +224,46 @@ static long plpar_int_sync(unsigned long flags, unsigned long lisn)
 	return 0;
 }
 
-#define XIVE_SRC_H_INT_ESB     (1ull << (63 - 60)) /* TODO */
+#define XIVE_ESB_FLAG_STORE (1ull << (63 - 63))
+
+static long plpar_int_esb(unsigned long flags,
+			  unsigned long lisn,
+			  unsigned long offset,
+			  unsigned long in_data,
+			  unsigned long *out_data)
+{
+	unsigned long retbuf[PLPAR_HCALL_BUFSIZE];
+	long rc;
+
+	pr_devel("H_INT_ESB flags=%lx lisn=%lx offset=%lx in=%lx\n",
+		flags,  lisn, offset, in_data);
+
+	rc = plpar_hcall(H_INT_ESB, retbuf, flags, lisn, offset, in_data);
+	if (rc) {
+		pr_err("H_INT_ESB lisn=%ld offset=%ld returned %ld\n",
+		       lisn, offset, rc);
+		return  rc;
+	}
+
+	*out_data = retbuf[0];
+
+	return 0;
+}
+
+static u64 xive_spapr_esb_rw(u32 lisn, u32 offset, u64 data, bool write)
+{
+	unsigned long read_data;
+	long rc;
+
+	rc = plpar_int_esb(write ? XIVE_ESB_FLAG_STORE : 0,
+			   lisn, offset, data, &read_data);
+	if (rc)
+		return -1;
+
+	return write ? 0 : read_data;
+}
+
+#define XIVE_SRC_H_INT_ESB     (1ull << (63 - 60))
 #define XIVE_SRC_LSI           (1ull << (63 - 61))
 #define XIVE_SRC_TRIGGER       (1ull << (63 - 62))
 #define XIVE_SRC_STORE_EOI     (1ull << (63 - 63))
@@ -244,6 +283,8 @@ static int xive_spapr_populate_irq_data(u32 hw_irq, struct xive_irq_data *data)
 	if (rc)
 		return  -EINVAL;
 
+	if (flags & XIVE_SRC_H_INT_ESB)
+		data->flags  |= XIVE_IRQ_FLAG_H_INT_ESB;
 	if (flags & XIVE_SRC_STORE_EOI)
 		data->flags  |= XIVE_IRQ_FLAG_STORE_EOI;
 	if (flags & XIVE_SRC_LSI)
@@ -487,6 +528,7 @@ static const struct xive_ops xive_spapr_ops = {
 	.setup_cpu		= xive_spapr_setup_cpu,
 	.teardown_cpu		= xive_spapr_teardown_cpu,
 	.sync_source		= xive_spapr_sync_source,
+	.esb_rw			= xive_spapr_esb_rw,
 #ifdef CONFIG_SMP
 	.get_ipi		= xive_spapr_get_ipi,
 	.put_ipi		= xive_spapr_put_ipi,
diff --git a/arch/powerpc/sysdev/xive/xive-internal.h b/arch/powerpc/sysdev/xive/xive-internal.h
index dd1e2022cce4..f34abed0c05f 100644
--- a/arch/powerpc/sysdev/xive/xive-internal.h
+++ b/arch/powerpc/sysdev/xive/xive-internal.h
@@ -47,6 +47,7 @@ struct xive_ops {
 	void	(*update_pending)(struct xive_cpu *xc);
 	void	(*eoi)(u32 hw_irq);
 	void	(*sync_source)(u32 hw_irq);
+	u64	(*esb_rw)(u32 hw_irq, u32 offset, u64 data, bool write);
 #ifdef CONFIG_SMP
 	int	(*get_ipi)(unsigned int cpu, struct xive_cpu *xc);
 	void	(*put_ipi)(unsigned int cpu, struct xive_cpu *xc);
-- 
2.13.5