[PATCH v2 00/10] spi: spi-mem: Add driver for Aspeed SMC controllers

Cédric Le Goater
2022-03-02T17:34:53Z

Hi,

This series adds a new SPI driver using the spi-mem interface for the
Aspeed static memory controllers of the AST2600, AST2500 and AST2400
SoCs.

* AST2600 Firmware SPI Memory Controller (FMC)
* AST2600 SPI Flash Controller (SPI1 and SPI2)
* AST2500 Firmware SPI Memory Controller (FMC)
* AST2500 SPI Flash Controller (SPI1 and SPI2)
* AST2400 New Static Memory Controller (also referred as FMC)
* AST2400 SPI Flash Controller (SPI)

It is based on the current OpenBMC kernel driver [1], using directly
the MTD SPI-NOR interface and on a patchset [2] previously proposed
adding support for the AST2600 only. This driver takes a slightly
different approach to cover all 6 controllers.

It does not make use of the controller register disabling Address and
Data byte lanes because is not available on the AST2400 SoC. We could
introduce a specific handler for new features available on recent SoCs
if needed. As there is not much difference on performance, the driver
chooses the common denominator: "User mode" which has been heavily
tested in [1]. "User mode" is also used as a fall back method when
flash device mapping window is too small.

Problems to address with spi-mem were the configuration of the mapping
windows and the calibration of the read timings. The driver handles
them in the direct mapping handler when some knowledge on the size of
the flash device is know. It is not perfect but not incorrect either.
The algorithm is one from [1] because it doesn't require the DMA
registers which are not available on all controllers.

Direct mapping for writes is not supported (yet). I have seen some
corruption with writes and I preferred to use the safer and proven
method of the initial driver [1]. We can improve that later.

The driver supports Quad SPI RX transfers on the AST2600 SoC but it
didn't have the expected results. Therefore it is not activated yet.
There are some issues on the pinctrl to investigate first.

The series does not remove the current Aspeed SMC driver but prepares
ground for its removal by changing its CONFIG option. This last step
can be addressed as a followup when the new driver using the spi-mem
interface has been sufficiently exposed.

Tested on:

* OpenPOWER Palmetto (AST2400)
* Facebook Wedge 100 BMC (AST2400) by Tao Ren <rentao.bupt@gmail.com>
* Evaluation board (AST2500)
* Inspur FP5280G2 BMC (AST2500) by John Wang <wangzq.jn@gmail.com>
* Facebook Backpack CMM BMC (AST2500) by Tao Ren <rentao.bupt@gmail.com>
* OpenPOWER Witherspoon (AST2500)
* Evaluation board (AST2600 A0 and A3)
* Rainier board (AST2600)

[1] https://github.com/openbmc/linux/blob/dev-5.15/drivers/mtd/spi-nor/controllers/aspeed-smc.c
[2] https://patchwork.ozlabs.org/project/linux-aspeed/list/?series=212394

Thanks,

C.

Changes in v2:

- Fixed dt_binding_check warnings (Rob)
- New entry in MAINTAINERS
- Addressed Lukas comments regarding the SPI controller registration
and device removal. Checked with driver bind/unbind
- Introduced setup and cleanup handlers and removed routine looping
on the DT children properties (Pratyush)
- Clarified in commit log requirements for training.
- Removed defconfig changes of patch 1 since they were reverted in
the last patch (Joel)

Cédric Le Goater (10):
mtd: spi-nor: aspeed: Rename Kconfig option
ARM: dts: aspeed: Adjust "reg" property of FMC/SPI controllers
dt-bindings: spi: Add Aspeed SMC controllers device tree binding
spi: spi-mem: Add driver for Aspeed SMC controllers
spi: aspeed: Add support for direct mapping
spi: aspeed: Adjust direct mapping to device size
spi: aspeed: Workaround AST2500 limitations
spi: aspeed: Add support for the AST2400 SPI controller
spi: aspeed: Calibrate read timings
ARM: dts: aspeed: Enable Dual SPI RX transfers

drivers/spi/spi-aspeed-smc.c | 1186 +++++++++++++++++
.../bindings/spi/aspeed,ast2600-fmc.yaml | 90 ++
MAINTAINERS | 10 +
arch/arm/boot/dts/aspeed-g4.dtsi | 12 +-
arch/arm/boot/dts/aspeed-g5.dtsi | 16 +-
arch/arm/boot/dts/aspeed-g6.dtsi | 17 +-
drivers/mtd/spi-nor/controllers/Kconfig | 4 +-
drivers/mtd/spi-nor/controllers/Makefile | 2 +-
drivers/spi/Kconfig | 11 +
drivers/spi/Makefile | 1 +
10 files changed, 1330 insertions(+), 19 deletions(-)
create mode 100644 drivers/spi/spi-aspeed-smc.c
create mode 100644 Documentation/devicetree/bindings/spi/aspeed,ast2600-fmc.yaml

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2.34.1