Re: [PATCH 2/5] genirq: Allocate IRQ descriptors at boot time for !SPARSEIRQ

[Shanker Donthineni]

On 1/31/23 03:16, Thomas Gleixner wrote:
> External email: Use caution opening links or attachments
>
>
> On Sun, Jan 29 2023 at 18:57, Shanker Donthineni wrote:
>
> > Remove the use of statically allocated arrays for IRQ descriptors.
> > Instead, allocate the necessary NR_IRQ descriptors during the boot
> > time in early_irq_init().
>
> That's not what I meant. I was pondering to remove !SPARSEIRQ
> completely.

It's touching many files to drop CONFIG_SPARSE_IRQ=n support. Worried
about removing !SPARSEIRQ without testing on legacy platforms.

Can work on this after moving it to maple tree?

 arch/arm/Kconfig           |  1 -
 arch/arm/include/asm/irq.h |  4 --
 arch/arm/kernel/irq.c      |  2 -
 arch/arm64/Kconfig         |  1 -
 arch/csky/Kconfig          |  1 -
 arch/loongarch/Kconfig     |  1 -
 arch/microblaze/Kconfig    |  1 -
 arch/nios2/Kconfig         |  1 -
 arch/openrisc/Kconfig      |  1 -
 arch/powerpc/Kconfig       |  1 -
 arch/riscv/Kconfig         |  1 -
 arch/s390/Kconfig          |  1 -
 arch/sh/Kconfig            |  1 -
 arch/sparc/Kconfig         |  1 -
 arch/x86/Kconfig           |  1 -
 drivers/irqchip/Kconfig    |  5 ---
 include/linux/irqdesc.h    |  8 ----
 kernel/irq/Kconfig         | 17 --------
 kernel/irq/chip.c          |  5 ---
 kernel/irq/internals.h     | 10 -----
 kernel/irq/irqdesc.c       | 88 --------------------------------------
 kernel/irq/irqdomain.c     | 14 +++---
 22 files changed, 6 insertions(+), 160 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 43c7773b89ae..d4fc6c549660 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -134,7 +134,6 @@ config ARM
        select PCI_SYSCALL if PCI
        select PERF_USE_VMALLOC
        select RTC_LIB
-       select SPARSE_IRQ if !(ARCH_FOOTBRIDGE || ARCH_RPC)
        select SYS_SUPPORTS_APM_EMULATION
        select THREAD_INFO_IN_TASK
        select TIMER_OF if OF
diff --git a/arch/arm/include/asm/irq.h b/arch/arm/include/asm/irq.h
index a7c2337b0c7d..6d4ff82c40cf 100644
--- a/arch/arm/include/asm/irq.h
+++ b/arch/arm/include/asm/irq.h
@@ -4,11 +4,7 @@

...

-#ifndef CONFIG_SPARSE_IRQ
-#include <mach/irqs.h>
-#else
 #define NR_IRQS NR_IRQS_LEGACY
-#endif

...
# Make sparse irq Kconfig switch below available
-config MAY_HAVE_SPARSE_IRQ
-       bool
-
 # Legacy support, required for itanic
 config GENERIC_IRQ_LEGACY
        bool
@@ -107,19 +103,6 @@ config GENERIC_IRQ_RESERVATION_MODE
 config IRQ_FORCED_THREADING
        bool


> That allocation does not buy us much.

Agree, not much value other than reducing kernel binary size. I will drop
this patch in v2.

Thanks,
Shanker