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

[Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>]

2015-03-09 1:29 GMT+01:00 Stefan Agner <stefan@xxxxxxxx>:
> 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@xxxxxxxxx>
>> ---
>>  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

I did something similar in my first version.

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

Yes, it is worth for these small devices.

>
> Acked-by: Stefan Agner <stefan@xxxxxxxx>
>

Thanks for the review,
Maxime
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