From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ludovic BARRE Subject: Re: [PATCH 1/6] ARM: stm32: prepare stm32 family to welcome armv7 architecture Date: Mon, 11 Dec 2017 15:22:00 +0100 Message-ID: <9ef92e81-fdd2-fa71-1e87-f797a191d215@st.com> References: <1512742277-28205-1-git-send-email-ludovic.Barre@st.com> <1512742277-28205-2-git-send-email-ludovic.Barre@st.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Arnd Bergmann , Linus Walleij Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Alexandre Torgue , "linux-kernel@vger.kernel.org" , Russell King , Rob Herring , Maxime Coquelin , Linux ARM List-Id: devicetree@vger.kernel.org On 12/11/2017 02:40 PM, Arnd Bergmann wrote: > On Mon, Dec 11, 2017 at 11:25 AM, Linus Walleij > wrote: >> On Fri, Dec 8, 2017 at 3:11 PM, Ludovic Barre wrote: >> >>> From: Ludovic Barre >>> >>> This patch prepares the STM32 machine for the integration of Cortex-A >>> based microprocessor (MPU), on top of the existing Cortex-M >>> microcontroller family (MCU). Since both MCUs and MPUs are sharing >>> common hardware blocks we can keep using ARCH_STM32 flag for most of >>> them. If a hardware block is specific to one family we can use either >>> ARCH_STM32_MCU or ARCH_STM32_MPU flag. >>> >>> Signed-off-by: Ludovic Barre > > To what degree do we need to treat them as separate families > at all then? I wonder if the MCU/MPU distinction is always that > clear along the Cortex-M/Cortex-A separation, especially if > we ever get to a chip that has both types of cores. What > exactly would we miss if we do away with the ARCH_STM32_MCU > symbol here? This patch series extends the existing STM32 microcontrollers (MCUs) family to microprocessors (MPUs). Now, ARCH_STM32 groups STM32 chips with Cortex-M or Cortex-A cores. But each core has different infrastructure mpu vs mmu; nvic vs gic; systick vs arch_timer ... So, ARCH_STM32_MCU/ARCH_STM32_MPU allow to define these specific blocks. br Ludo > >> So yesterdays application processors are todays MCU processors. >> >> I said this on a lecture for control systems a while back and >> stated it as a reason I think RTOSes are not really seeing a bright >> future compared to Linux. >> >> It happened quicker than I thought though, interesting. > > I think there is still lots of room for smaller RTOS in the long run, > but it's likely that the 'MPU + external DRAM' design point will > shift further to Linux, as there isn't really a benefit in squeezing > in anything smaller when the minimum is 32MB or 128MB of > RAM, depending on the interface. > > For on-chip eDRAM or SRAM based MPUs, that doesn't hold > true, the memory size is what drives the cost here. > > Arnd >