linux-kernel - Re: [PATCH v2 02/18] ARM: ARMv7M: Enlarge vector table to 256 entries

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Date:	Mon, 09 Mar 2015 01:29:28 +0100
From:	Stefan Agner <stefan@...er.ch>
To:	Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc:	u.kleine-koenig@...gutronix.de, afaerber@...e.de,
	geert@...ux-m68k.org, Rob Herring <robh+dt@...nel.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Jonathan Corbet <corbet@....net>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
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	Nikolay Borisov <Nikolay.Borisov@....com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Kees Cook <keescook@...omium.org>,
	Michal Marek <mmarek@...e.cz>, linux-doc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-gpio@...r.kernel.org,
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	linux-api@...r.kernel.org
Subject: Re: [PATCH v2 02/18] ARM: ARMv7M: Enlarge vector table to 256 entries

On 2015-02-20 19:01, Maxime Coquelin wrote:
> From Cortex-M reference manuals, the nvic supports up to 240 interrupts.
> So the number of entries in vectors table is up to 256.
> 
> This patch adds a new config flag to specify the number of external interrupts.
> Some ifdeferies are added in order to respect the natural alignment without
> wasting too much space on smaller systems.
> 
> Signed-off-by: Maxime Coquelin <mcoquelin.stm32@...il.com>
> ---
>  arch/arm/kernel/entry-v7m.S | 13 +++++++++----
>  arch/arm/mm/Kconfig         | 15 +++++++++++++++
>  2 files changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/kernel/entry-v7m.S b/arch/arm/kernel/entry-v7m.S
> index 8944f49..68cde36 100644
> --- a/arch/arm/kernel/entry-v7m.S
> +++ b/arch/arm/kernel/entry-v7m.S
> @@ -117,9 +117,14 @@ ENTRY(__switch_to)
>  ENDPROC(__switch_to)
>  
>  	.data
> -	.align	8
> +#if CONFIG_CPUV7M_NUM_IRQ <= 112
> +	.align	9
> +#else
> +	.align	10
> +#endif
> +
>  /*
> - * Vector table (64 words => 256 bytes natural alignment)
> + * Vector table (Natural alignment need to be ensured)
>   */
>  ENTRY(vector_table)
>  	.long	0			@ 0 - Reset stack pointer
> @@ -138,6 +143,6 @@ ENTRY(vector_table)
>  	.long	__invalid_entry		@ 13 - Reserved
>  	.long	__pendsv_entry		@ 14 - PendSV
>  	.long	__invalid_entry		@ 15 - SysTick
> -	.rept	64 - 16
> -	.long	__irq_entry		@ 16..64 - External Interrupts
> +	.rept	CONFIG_CPUV7M_NUM_IRQ
> +	.long	__irq_entry		@ External Interrupts
>  	.endr
> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> index c43c714..27eb835 100644
> --- a/arch/arm/mm/Kconfig
> +++ b/arch/arm/mm/Kconfig
> @@ -604,6 +604,21 @@ config CPU_USE_DOMAINS
>  	  This option enables or disables the use of domain switching
>  	  via the set_fs() function.
>  
> +config CPUV7M_NUM_IRQ
> +	int "Number of external interrupts connected to the NVIC"
> +	depends on CPU_V7M
> +	default 90 if ARCH_STM32
> +	default 38 if ARCH_EFM32
> +	default 240
> +	help
> +	  This option indicates the number of interrupts connected to the NVIC.
> +	  The value can be larger than the real number of interrupts supported
> +	  by the system, but must not be lower.
> +	  The default value is 240, corresponding to the maximum number of
> +	  interrupts supported by the NVIC on Cortex-M family.
> +
> +	  If unsure, keep default value.
> +
>  #
>  # CPU supports 36-bit I/O
>  #

I sent a patch which extended that vector table some weeks ago:
https://lkml.org/lkml/2014/12/29/296

But your solution is definitely more flexible, and given that we deal
with small devices here, it's worth saving memory.

Acked-by: Stefan Agner <stefan@...er.ch>

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