Hi Simon,
On 2/7/20 18:10, Simon Glass wrote:
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.
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.
Thanks for your hard work on this topic.
I think that there is great value in this research and in this
conclusion. It is clear that there two different approaches, but I feel
that the improvement to the current DM implementation would have a
higher impact in the community.
Since the first version of this proposal I have been thinking in a
solution that takes some of the advantages of tiny-dm idea but that does
not require so much effort. This seems to be aligned with what you have
been explaining in this section.
I found interesting your proposal about simplification some data
structures. In this sense one of my ideas, a bit biased by some of the
improvements in dtoc, is to change the the definition of struct driver
based on if OF_PLATDATA is enabled, and in this case remove some
properties.
struct driver {
#if !CONFIG_IS_ENABLED(OF_PLATDATA)
char *name;
#endif
enum uclass_id id;
#if !CONFIG_IS_ENABLED(OF_PLATDATA)
const struct udevice_id *of_match;
#endif
int (*bind)(struct udevice *dev);
int (*probe)(struct udevice *dev);
int (*remove)(struct udevice *dev);
int (*unbind)(struct udevice *dev);
int (*ofdata_to_platdata)(struct udevice *dev);
int (*child_post_bind)(struct udevice *dev);
int (*child_pre_probe)(struct udevice *dev);
int (*child_post_remove)(struct udevice *dev);
int priv_auto_alloc_size;
int platdata_auto_alloc_size;
int per_child_auto_alloc_size;
int per_child_platdata_auto_alloc_size;
const void *ops; /* driver-specific operations */
uint32_t flags;
#if CONFIG_IS_ENABLED(ACPIGEN)
struct acpi_ops *acpi_ops;
#endif
};
By just removing those properties, we save some bytes as we get rid of
several strings. Also maybe it would be nice to add some macros to make
it cleaner in drivers to use or not those properties, instead of adding
lots of #if.
I feel, as you clearly expressed, that some additional refactotring can
be made to make the logic be more similar to the tiny-dm one. I also
found interesting that several of your proposals will have impact in
U-Boot, not only in TPL/SPL.
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
Regards,
Walter
