Implemention of RTEMS-libbsd FDT support for BBB

The previous blog article describes how to implement FDT on RTEMS. This article will show you how to implement FDT support on RTEMS-libbsd.

The implementation of the rtems-libbsd management bus is in the nexus-devices.h file, that is, rtemsbsd/include/bsp/nexus-devices.h

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33.   
34. #if !defined(BSP_NEXUS_DEVICES_h)  
35. #define BSP_NEXUS_DEVICES_h  
36.   
37. #include <bsp.h>  
38.   
39. #include <rtems/bsd/bsd.h>  
40. #include <machine/rtems-bsd-nexus-bus.h>  
41.   
42.   
43. #if defined(LIBBSP_ARM_REALVIEW_PBX_A9_BSP_H)  
44.   
45. #include <bsp/irq.h>  
46.   
47. RTEMS_BSD_DRIVER_SMC0(0x4e000000,  RVPBXA9_IRQ_ETHERNET);  
48.   
49. #elif defined(LIBBSP_ARM_LPC32XX_BSP_H)  
50.   
51. #include <bsp/irq.h>  
52.   
53. RTEMS_BSD_DRIVER_LPC32XX_PWR;  
54. RTEMS_BSD_DRIVER_LPC32XX_LPE;  
55. RTEMS_BSD_DRIVER_ICSPHY;  
56. RTEMS_BSD_DRIVER_LPC32XX_OHCI;  
57. SYSINIT_DRIVER_REFERENCE(usbus, ohci);  
58. RTEMS_BSD_DRIVER_USB;  
59. RTEMS_BSD_DRIVER_USB_MASS;  
60.   
61. #elif defined(LIBBSP_M68K_GENMCF548X_BSP_H)  
62.   
63. RTEMS_BSD_DRIVER_FEC;  
64.   
65. #elif defined(LIBBSP_ARM_XILINX_ZYNQ_BSP_H)  
66.   
67. #include <bsp/irq.h>  
68.   
69. RTEMS_BSD_DRIVER_XILINX_ZYNQ_SLCR;  
70. RTEMS_BSD_DRIVER_XILINX_ZYNQ_CGEM0(ZYNQ_IRQ_ETHERNET_0);  
71. RTEMS_BSD_DRIVER_E1000PHY;  
72.   
73. #elif defined(LIBBSP_ARM_ATSAM_BSP_H)  
74.   
75. RTEMS_BSD_DRIVER_USB;  
76. RTEMS_BSD_DRIVER_USB_MASS;  
77.   
78. #elif defined(LIBBSP_ARM_ALTERA_CYCLONE_V_BSP_H)  
79.   
80. #include <bsp/socal/hps.h>  
81. #include <bsp/irq.h>  
82.   
83. RTEMS_BSD_DRIVER_DWC0((unsigned long) ALT_EMAC1_ADDR,  
84.               ALT_INT_INTERRUPT_EMAC1_IRQ);  
85. RTEMS_BSD_DRIVER_MIPHY;  
86. RTEMS_BSD_DRIVER_DWCOTG0((unsigned long) ALT_USB1_ADDR,  
87.              ALT_INT_INTERRUPT_USB1_IRQ);  
88. RTEMS_BSD_DRIVER_DWC_MMC;  
89. RTEMS_BSD_DRIVER_MMC;  
90. RTEMS_BSD_DRIVER_USB;  
91. RTEMS_BSD_DRIVER_USB_MASS;  
92.   
93. #elif defined(LIBBSP_ARM_LPC24XX_BSP_H)  
94.   
95. RTEMS_BSD_DEFINE_NEXUS_DEVICE(ohci, 0, 0, NULL);  
96. SYSINIT_DRIVER_REFERENCE(usbus, ohci);  
97. RTEMS_BSD_DRIVER_USB;  
98. RTEMS_BSD_DRIVER_USB_MASS;  
99.   
100. #elif defined(LIBBSP_I386_PC386_BSP_H)  
101.   
102. RTEMS_BSD_DRIVER_PC_LEGACY;  
103. RTEMS_BSD_DRIVER_PCI_LEM;  
104. RTEMS_BSD_DRIVER_PCI_IGB;  
105. RTEMS_BSD_DRIVER_PCI_EM;  
106. RTEMS_BSD_DRIVER_PCI_RE;  
107. RTEMS_BSD_DRIVER_REPHY;  
108.   
109. #elif defined(LIBBSP_POWERPC_QORIQ_BSP_H)  
110.   
111. #if !QORIQ_CHIP_IS_T_VARIANT(QORIQ_CHIP_VARIANT)  
112.   
113. #include <bsp/irq.h>  
114.   
115. RTEMS_BSD_DEFINE_NEXUS_DEVICE(ofwbus, 0, 0, NULL);  
116. SYSINIT_DRIVER_REFERENCE(simplebus, ofwbus);  
117. SYSINIT_DRIVER_REFERENCE(tsec, simplebus);  
118. SYSINIT_DRIVER_REFERENCE(ukphy, miibus);  
119.   
120. #endif /* !QORIQ_CHIP_IS_T_VARIANT(QORIQ_CHIP_VARIANT) */  
121.   
122. #endif  
123.   
124. #endif  

As you can see, there is no support for BBB, so you need to add the following fields:

1. #elif defined(LIBBSP_ARM_BEAGLE_BSP_H)  

Then, to add bus support, FreeBSD's device tree is root_bus, the bus, then nexus mounts on root_bus, then ofwbus mounts on nexus, and then simplebus hangs on ofwbus. Then other uhub or other devices are mounted on the simplebus.

Therefore, the following code needs to be added:

1. RTEMS_BSD_DEFINE_NEXUS_DEVICE(ofwbus, 0, 0, NULL);  
2. SYSINIT_DRIVER_REFERENCE(simplebus, ofwbus);  
3. SYSINIT_DRIVER_REFERENCE(ti_scm, simplebus);  
4. SYSINIT_DRIVER_REFERENCE(am335x_prcm, simplebus);  
5. SYSINIT_DRIVER_REFERENCE(usbss, simplebus);  
6. SYSINIT_DRIVER_REFERENCE(musbotg, usbss);  

The first line indicates that the ofwbus is mounted on the nexus, and the other lines are other mount relationships. This enables FDT support to be implemented at the BSP layer.

In addition, looking at the opt_platform.h file shows that if you need to enable FDT, you should also define the macro BSP_FDT_IS_SUPPORTED.

Therefore, we need to add in the bsp.h of the RTEMS source code:

1. #define BSP_FDT_IS_SUPPORTED  

That's the way RTEMS-libbsd adds FDT support.