Hi Heinrich,
On Thu, 2 Jul 2020 at 20:24, Heinrich Schuchardt xypron.glpk@gmx.de wrote:
Am 2. Juli 2020 23:10:01 MESZ schrieb Simon Glass sjg@chromium.org:
This series provides a proposed enhancement to driver model to reduce overhead in SPL.
These patches should not be reviewed other than to comment on the approach. The code is all lumped together in a few patches and so cannot be applied as is.
For now, the source tree is available at:
https://gitlab.denx.de/u-boot/custodians/u-boot-dm/-/tree/dtoc-working
Comments welcome!
Benefits (good news)
As an example of the impact of tiny-dm, chromebook_jerry is converted to use it. This shows approximately a 30% reduction in code and data size and a 85% reduction in malloc() space over of-platdata:
text data bss dec hex filename 25248 1836 12 27096 69d8 spl/u-boot-spl (original with DT) 19727 3436 12 23175 5a87 spl/u-boot-spl (OF_PLATDATA) 78% 187% 100% 86% as %age of original
13784 1408 12 15204 3b64 spl/u-boot-spl (SPL_TINY) 70% 41% 100% 66% as %age of platdata 55% 77% 100% 56% as %age of original
SPL malloc() usage drops from 944 bytes (OF_PLATDATA) to 116 (SPL_TINY).
Overall the 'overhead' of tiny-dm is much less than the full driver model. Code size is currently about 600 bytes for these functions on Thumb2:
00000054 T tiny_dev_probe 00000034 T tiny_dev_get_by_drvdata 00000024 T tiny_dev_find 0000001a T tiny_dev_get 0000003c T tinydev_alloc_data 0000002a t tinydev_lookup_data 00000022 T tinydev_ensure_data 00000014 T tinydev_get_data 00000004 T tinydev_get_parent
Effort (bad news)
Unfortunately it is quite a bit of work to convert drivers over to tiny-dm. First, the of-platdata conversion must be done. But on top of that, tiny-dm needs entirely separate code for dealing with devices. This means that instead of 'struct udevice' and 'struct uclass' there is just 'struct tinydev'. Each driver and uclass must be modified to support both, pulling common code into internal static functions.
The code size reductions sound quite impressive.
Somehow I have missed the start of your investigation. Could you, please, summarize what the main differences between tiny DM and the current DM are and explain why tiny DM cannot be used in main U-Boot.
See patch 2 (doc/driver-model/tiny-dm.rst). I probably didn't send out v1 widely enough, but it was only a starting point then.
It is quite limited and it would be fiddly to use in U-Boot proper. Things like automatic power domains, uclass features like setting up a bus and full devicetree access are not available with tiny DM.
Regards, Simon
Best regards
Heinrich
Another option
Note: It is assumed that any board that is space-contrained should use of-platdata in SPL (see doc/driver-model/of-plat.rst). This is shown to reduce device-tree overhead by approximately 4KB.
Designing tiny-dm has suggested a number of things that could be changed in the current driver model to make it more space-efficient for TPL and SPL. The ones with least impact on driver code are (CS=reduces code size, DS=reduces data size):
CS - drop driver_bind() and create devices (struct udevice) at build-time CS - allocate all device- and uclass-private data at build-time CS - remove all but the basic operations for each uclass (e.g. SPI flash only supports reading) DS - use 8-bit indexes instead of 32/64-bit pointers for device pointers possible since these are created at build-time) DS - use singly-linked lists DS - use 16-bit offsets to private data, instead of 32/64-bit pointers (possible since it is all in SRAM relative to malloc() base, presumably word-aligned and < 256KB) DS - move private pointers into a separate data structure so that NULLs are not stored CS / DS - Combine req_seq and seq and calculate the new value at build-time
More difficult are:
DS - drop some of the lesser-used driver and uclass methods DS - drop all uclass methods except init() DS - drop all driver methods except probe() CS / DS - drop uclasses and require drivers to manually call uclass functions
Even with all of this we would not reach tiny-dm and it would muddy up the driver-model datas structures. But we might come close to tiny-dm on size and there are some advantages:
- much of the benefit would apply to all boards that use of-platdata
(i.e. with very little effort on behalf of board maintainers)
- the impact on the code base is much less (we keep a single, unified
driver mode in SPL and U-Boot proper)
Overall I think it is worth looking at this option. While it doesn't have the 'nuclear' impact of tiny-dm, neither does it mess with the U-Boot driver code as much and it is easier to learn.
Changes in v2:
- Various updates, and ported to chromebook_jerry (rockchip)
Simon Glass (3): dm: Driver and uclass changes for tiny-dm dm: Arch-specific changes for tiny-dm dm: Core changes for tiny-dm
arch/arm/dts/rk3288-u-boot.dtsi | 17 +- arch/arm/dts/rk3288-veyron.dtsi | 26 +- arch/arm/dts/rk3288.dtsi | 3 + arch/arm/include/asm/arch-rockchip/clock.h | 9 + .../include/asm/arch-rockchip/sdram_rk3288.h | 21 ++ arch/arm/include/asm/arch-rockchip/spi.h | 1 + arch/arm/include/asm/io.h | 18 + arch/arm/mach-rockchip/rk3288/clk_rk3288.c | 46 +++ arch/arm/mach-rockchip/rk3288/rk3288.c | 2 + arch/arm/mach-rockchip/rk3288/syscon_rk3288.c | 45 +-- arch/arm/mach-rockchip/sdram.c | 33 +- arch/sandbox/cpu/u-boot-spl.lds | 12 + arch/sandbox/dts/sandbox.dts | 3 +- arch/sandbox/dts/sandbox.dtsi | 2 +- arch/x86/cpu/apollolake/cpu_spl.c | 5 +- arch/x86/cpu/apollolake/uart.c | 56 ++++ arch/x86/dts/chromebook_coral.dts | 1 + arch/x86/lib/tpl.c | 4 +- board/Synology/ds109/ds109.c | 3 +- common/console.c | 2 +- common/log.c | 36 +- common/malloc_simple.c | 31 ++ common/spl/spl.c | 17 +- common/spl/spl_spi.c | 91 +++-- configs/chromebook_coral_defconfig | 1 + configs/chromebook_jerry_defconfig | 11 + configs/rock2_defconfig | 3 + doc/develop/debugging.rst | 35 ++ doc/driver-model/tiny-dm.rst | 315 +++++++++++++++++ drivers/clk/Kconfig | 54 +++ drivers/clk/Makefile | 4 +- drivers/clk/clk-uclass.c | 53 ++- drivers/clk/rockchip/clk_rk3288.c | 106 ++++-- drivers/core/Kconfig | 106 ++++++ drivers/core/Makefile | 3 + drivers/core/of_extra.c | 49 ++- drivers/core/regmap.c | 3 +- drivers/core/syscon-uclass.c | 68 +++- drivers/core/tiny.c | 249 ++++++++++++++ drivers/mtd/spi/Kconfig | 18 + drivers/mtd/spi/sf-uclass.c | 76 +++++ drivers/mtd/spi/sf_probe.c | 4 + drivers/mtd/spi/spi-nor-tiny.c | 166 ++++++++- drivers/ram/Kconfig | 18 + drivers/ram/ram-uclass.c | 12 + drivers/ram/rockchip/sdram_rk3188.c | 2 +- drivers/ram/rockchip/sdram_rk322x.c | 2 +- drivers/ram/rockchip/sdram_rk3288.c | 231 ++++++++----- drivers/ram/rockchip/sdram_rk3328.c | 2 +- drivers/ram/rockchip/sdram_rk3399.c | 2 +- drivers/reset/reset-rockchip.c | 4 +- drivers/serial/Kconfig | 38 +++ drivers/serial/ns16550.c | 195 +++++++++-- drivers/serial/sandbox.c | 59 +++- drivers/serial/serial-uclass.c | 77 +++++ drivers/serial/serial_omap.c | 2 +- drivers/serial/serial_rockchip.c | 59 ++++ drivers/spi/Kconfig | 18 + drivers/spi/Makefile | 2 + drivers/spi/rk_spi.c | 301 ++++++++++++----- drivers/spi/spi-uclass.c | 77 +++++ drivers/sysreset/Kconfig | 18 + drivers/sysreset/sysreset-uclass.c | 124 ++++--- drivers/sysreset/sysreset_rockchip.c | 61 +++- include/asm-generic/global_data.h | 7 +- include/clk-uclass.h | 11 + include/clk.h | 32 +- include/dm/device.h | 121 +++++++ include/dm/of_extra.h | 6 + include/dm/platdata.h | 20 +- include/dm/tiny_struct.h | 42 +++ include/linker_lists.h | 6 + include/linux/mtd/mtd.h | 23 +- include/linux/mtd/spi-nor.h | 22 ++ include/log.h | 6 + include/malloc.h | 3 + include/ns16550.h | 7 +- include/ram.h | 25 ++ include/regmap.h | 4 +- include/serial.h | 45 ++- include/spi.h | 31 ++ include/spi_flash.h | 7 + include/spl.h | 8 +- include/syscon.h | 2 + include/sysreset.h | 9 + scripts/Makefile.spl | 6 +- tools/dtoc/dtb_platdata.py | 316 +++++++++++++++--- tools/dtoc/dtoc_test_simple.dts | 12 +- tools/dtoc/fdt.py | 7 +- tools/dtoc/main.py | 9 +- tools/dtoc/test_dtoc.py | 91 ++++- tools/patman/tools.py | 4 +- 92 files changed, 3454 insertions(+), 540 deletions(-) create mode 100644 doc/develop/debugging.rst create mode 100644 doc/driver-model/tiny-dm.rst create mode 100644 drivers/core/tiny.c create mode 100644 include/dm/tiny_struct.h
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