[PATCH] genirq: allow selection of number of sparse irqs

[Daniel Walker <danielwa@cisco.com>]

Currently the maximum number of interrupters is capped at 8260 (64 +
8196) in most of the architectures were CONFIG_SPARSE_IRQ is selected.
This upper limit is not sufficient for couple of existing SoC's from
Marvell.
For eg: Octeon TX2 series of processors support a maximum of 32K
interrupters.

Allow configuration of the upper limit of the number of interrupts.

Cc: George Cherian <george.cherian@marvell.com>
Cc: sgoutham@marvell.com
Cc: "BOBBY Liu (bobbliu)" <bobbliu@cisco.com>
Cc: xe-linux-external@cisco.com
Signed-off-by: Daniel Walker <danielwa@cisco.com>
---
 kernel/irq/Kconfig     | 23 +++++++++++++++++++++++
 kernel/irq/internals.h | 10 +++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
index db3d174c53d4..b356217abcfe 100644
--- a/kernel/irq/Kconfig
+++ b/kernel/irq/Kconfig
@@ -125,6 +125,29 @@ config SPARSE_IRQ
 
 	  If you don't know what to do here, say N.
 
+choice
+	prompt "Select number of sparse irqs"
+	depends on SPARSE_IRQ
+	default SPARSE_IRQ_EXTEND_8K
+	help
+          Allows choosing the number of sparse irq's available on the
+          system. For each 8k of additional irqs added there is approximatly
+          1kb of kernel size increase.
+
+config SPARSE_IRQ_EXTEND_8K
+	bool "8k"
+
+config SPARSE_IRQ_EXTEND_16K
+	bool "16K"
+
+config SPARSE_IRQ_EXTEND_32K
+	bool "32K"
+
+config SPARSE_IRQ_EXTEND_64K
+	bool "64K"
+
+endchoice
+
 config GENERIC_IRQ_DEBUGFS
 	bool "Expose irq internals in debugfs"
 	depends on DEBUG_FS
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index f09c60393e55..25fe5abf6c16 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -12,7 +12,15 @@
 #include <linux/sched/clock.h>
 
 #ifdef CONFIG_SPARSE_IRQ
-# define IRQ_BITMAP_BITS	(NR_IRQS + 8196)
+# if defined(CONFIG_SPARSE_IRQ_EXTEND_8K)
+# define IRQ_BITMAP_BITS	(NR_IRQS + 8192 + 4)
+# elif defined(CONFIG_SPARSE_IRQ_EXTEND_16K)
+# define IRQ_BITMAP_BITS	(NR_IRQS + 16384 + 4)
+# elif defined(CONFIG_SPARSE_IRQ_EXTEND_32K)
+# define IRQ_BITMAP_BITS	(NR_IRQS + 32768 + 4)
+# elif defined(CONFIG_SPARSE_IRQ_EXTEND_64K)
+# define IRQ_BITMAP_BITS	(NR_IRQS + 65536 + 4)
+# endif
 #else
 # define IRQ_BITMAP_BITS	NR_IRQS
 #endif
-- 
2.25.1