Hi Rob, 2015-02-15 23:42 GMT+01:00 Rob Herring <robherring2@xxxxxxxxx>: > On Fri, Feb 13, 2015 at 2:42 AM, Maxime Coquelin > <mcoquelin.stm32@xxxxxxxxx> wrote: >> Hi Geert, >> >> 2015-02-12 21:34 GMT+01:00 Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>: >>> On Thu, Feb 12, 2015 at 6:45 PM, Maxime Coquelin >>> <mcoquelin.stm32@xxxxxxxxx> wrote: >>>> From Cortex-M4 and M7 reference manuals, the nvic supports up to 240 >>>> interrupts. So the number of entries in vectors table is 256. >>>> >>>> This patch adds the missing entries, and change the alignement, so that >>>> vector_table remains naturally aligned. >>> >>> Shouldn't this depend on ARCH_STM32, or some other M4 or M7 specific >>> Kconfig option, to avoid wasting the space on other CPUs? >> >> Actually, the STM32F429 has 90 interrupts, so it would need 106 >> entries in the vector table. >> The maximum of supported interrupts is not only for Cortex-M4 and M7, >> this is also true for Cortex-M3. >> >> I see two possibilities: >> 1 - We declare the vector table for the maximum supported number of >> IRQs, as this patch does. >> - Pro: it will be functionnal with all Cortex-M MCUs >> - Con: Waste of less than 1KB for memory > > The waste depends on the alignment size as well and could be up to > almost 2KB worst case. It varies depending on the padding. We should > try to place it so it always aligned and the wasted space is > minimized. Sorry, I just notice I didn't replied to all. That was my question: Do you mean by forcing its location in the arch/arm/kernel/vmlinux.lds.S file? Regards, Maxime > > Rob > >> 2 - We introduce a config flag that provides the number of interrupts >> - Pro: No more memory waste >> - Con: Need to declare a per MCU model config flag. >> >> Then, regarding the natural alignment, is there a way to ensure it >> depending on the value of a config flag? >> Or we should keep it at the maximum value possible? >> >> Any feedback will be appreciated, especially from Uwe who maintains >> the efm32 machine. >> >> Kind regards, >> Maxime -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
