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