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doc: driver-model: Convert of-plat.txt to reST
Convert plain text documentation to reStructuredText format and add it to Sphinx TOC tree. No essential content change. Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
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Bin Meng
Tom Rini
parent
6c49c22846
commit
45dbb4dd23
2 changed files with 106 additions and 88 deletions
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@ -12,3 +12,4 @@ Driver Model
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i2c-howto
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livetree
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migration
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of-plat
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@ -1,5 +1,7 @@
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Driver Model Compiled-in Device Tree / Platform Data
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====================================================
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.. SPDX-License-Identifier: GPL-2.0+
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Compiled-in Device Tree / Platform Data
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=======================================
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Introduction
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@ -40,36 +42,36 @@ There are many problems with this features. It should only be used when
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strictly necessary. Notable problems include:
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- Device tree does not describe data types. But the C code must define a
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type for each property. These are guessed using heuristics which
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are wrong in several fairly common cases. For example an 8-byte value
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is considered to be a 2-item integer array, and is byte-swapped. A
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boolean value that is not present means 'false', but cannot be
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included in the structures since there is generally no mention of it
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in the device tree file.
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type for each property. These are guessed using heuristics which
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are wrong in several fairly common cases. For example an 8-byte value
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is considered to be a 2-item integer array, and is byte-swapped. A
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boolean value that is not present means 'false', but cannot be
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included in the structures since there is generally no mention of it
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in the device tree file.
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- Naming of nodes and properties is automatic. This means that they follow
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the naming in the device tree, which may result in C identifiers that
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look a bit strange.
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the naming in the device tree, which may result in C identifiers that
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look a bit strange.
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- It is not possible to find a value given a property name. Code must use
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the associated C member variable directly in the code. This makes
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the code less robust in the face of device-tree changes. It also
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makes it very unlikely that your driver code will be useful for more
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than one SoC. Even if the code is common, each SoC will end up with
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a different C struct name, and a likely a different format for the
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platform data.
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the associated C member variable directly in the code. This makes
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the code less robust in the face of device-tree changes. It also
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makes it very unlikely that your driver code will be useful for more
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than one SoC. Even if the code is common, each SoC will end up with
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a different C struct name, and a likely a different format for the
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platform data.
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- The platform data is provided to drivers as a C structure. The driver
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must use the same structure to access the data. Since a driver
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normally also supports device tree it must use #ifdef to separate
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out this code, since the structures are only available in SPL.
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must use the same structure to access the data. Since a driver
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normally also supports device tree it must use #ifdef to separate
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out this code, since the structures are only available in SPL.
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- Correct relations between nodes are not implemented. This means that
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parent/child relations (like bus device iteration) do not work yet.
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Some phandles (those that are recognised as such) are converted into
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a pointer to platform data. This pointer can potentially be used to
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access the referenced device (by searching for the pointer value).
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This feature is not yet implemented, however.
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parent/child relations (like bus device iteration) do not work yet.
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Some phandles (those that are recognised as such) are converted into
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a pointer to platform data. This pointer can potentially be used to
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access the referenced device (by searching for the pointer value).
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This feature is not yet implemented, however.
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How it works
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@ -78,30 +80,34 @@ How it works
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The feature is enabled by CONFIG OF_PLATDATA. This is only available in
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SPL/TPL and should be tested with:
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#if CONFIG_IS_ENABLED(OF_PLATDATA)
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.. code-block:: c
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#if CONFIG_IS_ENABLED(OF_PLATDATA)
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A new tool called 'dtoc' converts a device tree file either into a set of
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struct declarations, one for each compatible node, and a set of
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U_BOOT_DEVICE() declarations along with the actual platform data for each
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device. As an example, consider this MMC node:
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sdmmc: dwmmc@ff0c0000 {
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compatible = "rockchip,rk3288-dw-mshc";
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clock-freq-min-max = <400000 150000000>;
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clocks = <&cru HCLK_SDMMC>, <&cru SCLK_SDMMC>,
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<&cru SCLK_SDMMC_DRV>, <&cru SCLK_SDMMC_SAMPLE>;
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clock-names = "biu", "ciu", "ciu_drv", "ciu_sample";
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fifo-depth = <0x100>;
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interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>;
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reg = <0xff0c0000 0x4000>;
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bus-width = <4>;
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cap-mmc-highspeed;
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cap-sd-highspeed;
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card-detect-delay = <200>;
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disable-wp;
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num-slots = <1>;
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pinctrl-names = "default";
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pinctrl-0 = <&sdmmc_clk>, <&sdmmc_cmd>, <&sdmmc_cd>, <&sdmmc_bus4>;
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.. code-block:: none
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sdmmc: dwmmc@ff0c0000 {
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compatible = "rockchip,rk3288-dw-mshc";
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clock-freq-min-max = <400000 150000000>;
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clocks = <&cru HCLK_SDMMC>, <&cru SCLK_SDMMC>,
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<&cru SCLK_SDMMC_DRV>, <&cru SCLK_SDMMC_SAMPLE>;
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clock-names = "biu", "ciu", "ciu_drv", "ciu_sample";
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fifo-depth = <0x100>;
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interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>;
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reg = <0xff0c0000 0x4000>;
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bus-width = <4>;
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cap-mmc-highspeed;
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cap-sd-highspeed;
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card-detect-delay = <200>;
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disable-wp;
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num-slots = <1>;
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pinctrl-names = "default";
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pinctrl-0 = <&sdmmc_clk>, <&sdmmc_cmd>, <&sdmmc_cd>, <&sdmmc_bus4>;
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vmmc-supply = <&vcc_sd>;
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status = "okay";
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u-boot,dm-pre-reloc;
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@ -112,52 +118,59 @@ Some of these properties are dropped by U-Boot under control of the
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CONFIG_OF_SPL_REMOVE_PROPS option. The rest are processed. This will produce
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the following C struct declaration:
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struct dtd_rockchip_rk3288_dw_mshc {
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fdt32_t bus_width;
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bool cap_mmc_highspeed;
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bool cap_sd_highspeed;
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fdt32_t card_detect_delay;
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fdt32_t clock_freq_min_max[2];
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struct phandle_1_arg clocks[4];
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bool disable_wp;
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fdt32_t fifo_depth;
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fdt32_t interrupts[3];
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fdt32_t num_slots;
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fdt32_t reg[2];
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fdt32_t vmmc_supply;
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};
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.. code-block:: c
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struct dtd_rockchip_rk3288_dw_mshc {
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fdt32_t bus_width;
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bool cap_mmc_highspeed;
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bool cap_sd_highspeed;
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fdt32_t card_detect_delay;
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fdt32_t clock_freq_min_max[2];
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struct phandle_1_arg clocks[4];
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bool disable_wp;
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fdt32_t fifo_depth;
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fdt32_t interrupts[3];
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fdt32_t num_slots;
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fdt32_t reg[2];
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fdt32_t vmmc_supply;
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};
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and the following device declaration:
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static struct dtd_rockchip_rk3288_dw_mshc dtv_dwmmc_at_ff0c0000 = {
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.fifo_depth = 0x100,
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.cap_sd_highspeed = true,
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.interrupts = {0x0, 0x20, 0x4},
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.clock_freq_min_max = {0x61a80, 0x8f0d180},
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.vmmc_supply = 0xb,
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.num_slots = 0x1,
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.clocks = {{&dtv_clock_controller_at_ff760000, 456},
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{&dtv_clock_controller_at_ff760000, 68},
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{&dtv_clock_controller_at_ff760000, 114},
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{&dtv_clock_controller_at_ff760000, 118}},
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.cap_mmc_highspeed = true,
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.disable_wp = true,
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.bus_width = 0x4,
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.u_boot_dm_pre_reloc = true,
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.reg = {0xff0c0000, 0x4000},
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.card_detect_delay = 0xc8,
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};
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U_BOOT_DEVICE(dwmmc_at_ff0c0000) = {
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.name = "rockchip_rk3288_dw_mshc",
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.platdata = &dtv_dwmmc_at_ff0c0000,
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.platdata_size = sizeof(dtv_dwmmc_at_ff0c0000),
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};
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.. code-block:: c
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static struct dtd_rockchip_rk3288_dw_mshc dtv_dwmmc_at_ff0c0000 = {
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.fifo_depth = 0x100,
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.cap_sd_highspeed = true,
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.interrupts = {0x0, 0x20, 0x4},
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.clock_freq_min_max = {0x61a80, 0x8f0d180},
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.vmmc_supply = 0xb,
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.num_slots = 0x1,
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.clocks = {{&dtv_clock_controller_at_ff760000, 456},
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{&dtv_clock_controller_at_ff760000, 68},
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{&dtv_clock_controller_at_ff760000, 114},
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{&dtv_clock_controller_at_ff760000, 118}},
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.cap_mmc_highspeed = true,
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.disable_wp = true,
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.bus_width = 0x4,
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.u_boot_dm_pre_reloc = true,
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.reg = {0xff0c0000, 0x4000},
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.card_detect_delay = 0xc8,
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};
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U_BOOT_DEVICE(dwmmc_at_ff0c0000) = {
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.name = "rockchip_rk3288_dw_mshc",
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.platdata = &dtv_dwmmc_at_ff0c0000,
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.platdata_size = sizeof(dtv_dwmmc_at_ff0c0000),
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};
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The device is then instantiated at run-time and the platform data can be
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accessed using:
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struct udevice *dev;
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struct dtd_rockchip_rk3288_dw_mshc *plat = dev_get_platdata(dev);
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.. code-block:: c
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struct udevice *dev;
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struct dtd_rockchip_rk3288_dw_mshc *plat = dev_get_platdata(dev);
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This avoids the code overhead of converting the device tree data to
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platform data in the driver. The ofdata_to_platdata() method should
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@ -173,7 +186,9 @@ each 'compatible' string.
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Where a node has multiple compatible strings, a #define is used to make them
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equivalent, e.g.:
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#define dtd_rockchip_rk3299_dw_mshc dtd_rockchip_rk3288_dw_mshc
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.. code-block:: c
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#define dtd_rockchip_rk3299_dw_mshc dtd_rockchip_rk3288_dw_mshc
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Converting of-platdata to a useful form
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@ -204,6 +219,8 @@ ofdata_to_platdata() method and wrapped with #if.
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For example:
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.. code-block:: c
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#include <dt-structs.h>
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struct mmc_platdata {
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@ -313,12 +330,12 @@ This is an implementation of an idea by Tom Rini <trini@konsulko.com>.
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Future work
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-----------
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- Consider programmatically reading binding files instead of device tree
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contents
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contents
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- Complete the phandle feature
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- Move to using a full Python libfdt module
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--
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Simon Glass <sjg@chromium.org>
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Google, Inc
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6/6/16
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Updated Independence Day 2016
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.. Simon Glass <sjg@chromium.org>
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.. Google, Inc
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.. 6/6/16
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.. Updated Independence Day 2016
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