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@xxxxxx>
---
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). I will have to modify some part of
the proposed bindings, and some updates will have to be done in the FMC2
bus driver. All these modifications will be part of V3.
Regards,
Christophe Kerello.
