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Date: Fri, 24 Apr 2020 18:42:59 +0200 From: Christophe Kerello <christophe.kerello@...com> To: Boris Brezillon <boris.brezillon@...labora.com> CC: Marek Vasut <marex@...x.de>, Lee Jones <lee.jones@...aro.org>, <mark.rutland@....com>, <devicetree@...r.kernel.org>, <vigneshr@...com>, <tony@...mide.com>, <richard@....at>, <linux-kernel@...r.kernel.org>, <robh+dt@...nel.org>, <linux-mtd@...ts.infradead.org>, <miquel.raynal@...tlin.com>, Geert Uytterhoeven <geert@...ux-m68k.org>, <linux-stm32@...md-mailman.stormreply.com> Subject: Re: [PATCH v2 02/12] mfd: stm32-fmc2: add STM32 FMC2 controller driver On 4/24/20 5:14 PM, Boris Brezillon wrote: > On Fri, 24 Apr 2020 13:47:34 +0200 > Christophe Kerello <christophe.kerello@...com> 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 <christophe.kerello@...com> >>>>>>> --- >>>>>>> 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 > Hi Boris, Thanks for your help. I was thinking about the bindings and I think that the bindings below are close to what has been done for Atmel EBI/Raw NAND bindings (in terms of structure of bindings if I have well understood). I think that these proposed bindings are very close to the first proposed version (V1/V2). fmc@...02000 { #address-cells = <2>; #size-cells = <1>; compatible = "st,stm32mp1-fmc2"; reg = <0x58002000 0x1000>; clocks = <&rcc FMC_K>; resets = <&rcc FMC_R>; ranges = <0 0 0x60000000 0x4000000>, /* EBI bank 1 */ <1 0 0x64000000 0x4000000>, /* EBI bank 2 */ <2 0 0x68000000 0x4000000>, /* EBI bank 3 */ <3 0 0x6c000000 0x4000000>, /* EBI bank 4 */ <4 0 0x80000000 0x4000000>, /* NAND common memory space */ <5 0 0x88000000 0x4000000>; /* NAND attribute memory space */ psram@0 { compatible = "mtd-ram"; reg = <0 0x00000000 0x100000>; bank-width = <2>; st,fmc2_ebi_cs_transaction_type = <1>; st,fmc2_ebi_cs_address_setup = <60>; st,fmc2_ebi_cs_data_setup = <30>; st,fmc2_ebi_cs_bus_turnaround = <5>; }; nand-controller@4 { #address-cells = <1>; #size-cells = <0>; compatible = "st,stm32mp15-fmc2"; reg = <4 0x00000000 0x1000>, <5 0x00010000 0x1000>, <5 0x00020000 0x1000>, <4 0x01000000 0x1000>, <5 0x01010000 0x1000>, <5 0x01020000 0x1000>; interrupts = <GIC_SPI 48 IRQ_TYPE_LEVEL_HIGH>; dmas = <&mdma1 20 0x2 0x12000a02 0x0 0x0>, <&mdma1 20 0x2 0x12000a08 0x0 0x0>, <&mdma1 21 0x2 0x12000a0a 0x0 0x0>; dma-names = "tx", "rx", "ecc"; nand@0 { reg = <0>; nand-on-flash-bbt; #address-cells = <1>; #size-cells = <1>; }; }; }; Regards, Christophe Kerello.
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