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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jS06B-0002do-DV; Fri, 24 Apr 2020 15:18:39 +0000 Received: from bhuna.collabora.co.uk ([46.235.227.227]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jS01z-0004Zd-Nx for linux-mtd@lists.infradead.org; Fri, 24 Apr 2020 15:14:22 +0000 Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: bbrezillon) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id 993952A2E0F; Fri, 24 Apr 2020 16:14:15 +0100 (BST) Date: Fri, 24 Apr 2020 17:14:12 +0200 From: Boris Brezillon To: Christophe Kerello Subject: Re: [PATCH v2 02/12] mfd: stm32-fmc2: add STM32 FMC2 controller driver Message-ID: <20200424171412.5f65ff05@collabora.com> In-Reply-To: <268ea231-eb4a-6144-c632-1bc8e9f21582@st.com> References: <1586966256-29548-1-git-send-email-christophe.kerello@st.com> <1586966256-29548-3-git-send-email-christophe.kerello@st.com> <20200424074517.GN3612@dell> <8b625f1c-9ded-c07a-a20e-8cd44c1ca46d@denx.de> <20200424105053.GC8414@dell> <268ea231-eb4a-6144-c632-1bc8e9f21582@st.com> Organization: Collabora X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200424_081420_102544_77C8D5C6 X-CRM114-Status: GOOD ( 32.31 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marek Vasut , mark.rutland@arm.com, vigneshr@ti.com, devicetree@vger.kernel.org, tony@atomide.com, richard@nod.at, linux-kernel@vger.kernel.org, robh+dt@kernel.org, linux-mtd@lists.infradead.org, miquel.raynal@bootlin.com, Geert Uytterhoeven , Lee Jones , linux-stm32@st-md-mailman.stormreply.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On Fri, 24 Apr 2020 13:47:34 +0200 Christophe Kerello wrote: > On 4/24/20 1:06 PM, Marek Vasut wrote: > > On 4/24/20 12:50 PM, Lee Jones wrote: > >> On Fri, 24 Apr 2020, Marek Vasut wrote: > >> > >>> On 4/24/20 9:45 AM, Lee Jones wrote: > >>>> On Wed, 15 Apr 2020, Christophe Kerello wrote: > >>>> > >>>>> The driver adds the support for the STMicroelectronics FMC2 controller > >>>>> found on STM32MP SOCs. > >>>>> > >>>>> The FMC2 functional block makes the interface with: synchronous and > >>>>> asynchronous static memories (such as PSNOR, PSRAM or other > >>>>> memory-mapped peripherals) and NAND flash memories. > >>>>> > >>>>> Signed-off-by: Christophe Kerello > >>>>> --- > >>>>> Changes in v2: > >>>>> - remove ops from stm32_fmc2 structure > >>>>> - add 2 APIs to manage FMC2 enable/disable > >>>>> - add 2 APIs to manage FMC2 NWAIT shared signal > >>>>> > >>>>> drivers/mfd/Kconfig | 12 +++ > >>>>> drivers/mfd/Makefile | 1 + > >>>>> drivers/mfd/stm32-fmc2.c | 136 +++++++++++++++++++++++++ > >>>>> include/linux/mfd/stm32-fmc2.h | 225 +++++++++++++++++++++++++++++++++++++++++ > >>>>> 4 files changed, 374 insertions(+) > >>>>> create mode 100644 drivers/mfd/stm32-fmc2.c > >>>>> create mode 100644 include/linux/mfd/stm32-fmc2.h > >>>>> > >>>>> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig > >>>>> index 2b20329..5260582 100644 > >>>>> --- a/drivers/mfd/Kconfig > >>>>> +++ b/drivers/mfd/Kconfig > >>>>> @@ -1922,6 +1922,18 @@ config MFD_ROHM_BD71828 > >>>>> Also included is a Coulomb counter, a real-time clock (RTC), and > >>>>> a 32.768 kHz clock gate. > >>>>> > >>>>> +config MFD_STM32_FMC2 > >>>>> + tristate "Support for FMC2 controllers on STM32MP SoCs" > >>>>> + depends on MACH_STM32MP157 || COMPILE_TEST > >>>>> + select MFD_CORE > >>>>> + select REGMAP > >>>>> + select REGMAP_MMIO > >>>>> + help > >>>>> + Select this option to enable STM32 FMC2 driver used for FMC2 External > >>>>> + Bus Interface controller and FMC2 NAND flash controller. This driver > >>>>> + provides core support for the STM32 FMC2 controllers, in order to use > >>>>> + the actual functionality of the device other drivers must be enabled. > >>>> > >>>> Not sure how many times I have to say this before people stop > >>>> attempting to pass these kinds of relationships off as MFDs: > >>>> > >>>> A memory device and its bus is not an MFD. In a similar vain to the > >>>> thousands of USB, I2C, SPI, PCI and the like devices that aren't MFDs > >>>> either. > >>>> > >>>> Please find another way to associate your device with its bus. > >>> > >>> This FMC2 is however an IP which can either operate external devices > >>> (like ethernet chip on this parallel bus) or external flashes (like NOR > >>> and NAND chips). > >> > >> I'm sure that it *can*. Although that's not its main purpose. > > > > I use it to operate KSZ8851-16MLL ethernet chip, which has async bus > > interface. Linux just didn't have support for that mode of operation > > thus far and the FMC was used to operate NANDs and NORs only. This > > series, or rather, the first three patches in this series, add support > > for operating other bus devices, like this ethernet controller. > > > >> The > >> clue is in the nomenclature ("Flexible *Memory* Controller"). Nor is > >> it how the device is being used in this submission: > >> > >> "The FMC2 functional block makes the interface with: synchronous and > >> asynchronous static memories (such as PSNOR, PSRAM or other > >> memory-mapped peripherals) and NAND flash memories." > >> > >> As I mentioned, this is just another memory device and its bus. > > > > I don't think it's _just_ a memory controller, it's more universal than > > that, see above. Note that SRAM interface basically boils down to > > anything which has external parallel bus, e.g. Davicom DM9000, that > > KSZ8851-16MLL etc. > > > >>> Can you provide a suggestion how this should be handled, if not as MFD? > >>> It seems to me, that this is a Multi-Function Device . > >> > >> Simply move it into the MTD or Memory subsystems and set up the > >> dependencies via Kconfig. > >> > >>> If this discussion is a recurring topic, is there some documentation > >>> which explains how such devices should be handled ? > >> > >> Not that I'm aware of. > > > > I see. > > > > Hi Lee, Marek, > > I will move this source code in the FMC2 bus driver. I think that I > should be able to manage the 2 controllers with 2 drivers (the FMC2 bus > driver and the FMC2 raw NAND driver). FWIW, that's what I did for the Atmel EBI (External Bus Interface) controller (see [1]). [1]https://elixir.bootlin.com/linux/v5.6/source/drivers/memory/atmel-ebi.c ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/