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How to write Platform Devices and Drivers with FPGA via GPMC

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How to write Platform Devices and Drivers with FPGA via GPMC

How to write Platform Devices and Drivers with FPGA via GPMC

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  • 1. How to write Platform Devices and Drivers with FPGA via GPMC Bo-Yi Wu 2011.06.15 http://blog.wu-boy.com
  • 2. What’s GPMC
    • 全名 General-Purpose Memory Controller
    • the device unified memory controller (UMC) dedicated to interfacing external memory devices.
      • NAND Flash
      • NOR Flash
      • FPGA (*)
    • 如果要更深入研究,請參考 TI 線上 Documentation
  • 3. 寫 GPMC Drive 跟 FPGA 溝通前
  • 4. 必須先瞭解什麼是 Platform Devices 和 Platform Drivers
  • 5. 撰寫 Driver Model 事先預備 Porting Drivers to New Driver Model
    • Driver Binding
    • Bus Types
    • Device Classes
    • Basic Device Structure
    • Managed Device Resource
    • Device Drivers
    • Device Interfaces
    • Platform Devices and Drivers
  • 6. Platform 架構
    • 參考 <linux/platform_device.h> 來瞭解 driver model 如何跟 platform bus 溝通
    • 用在 system-on-chip processors 或者是一些 &quot;legacy&quot; PC interconnects
  • 7. Platform devices
    • 請指定一個名稱用來 Driver Binding ,以及定義該 Devices 需要用到的 addresses 和 IRQs.
    struct platform_device { const char *name; u32 id; struct device dev; u32 num_resources; struct resource *resource; };
  • 8. Platform drivers
    • Platform drivers 走 Driver Model 標準規範,提供 probe 及 remove method ,它們提供 power 管理及關閉提醒等標準
  • 9. struct platform_driver { int (*probe)(struct platform_device *); int (*remove)(struct platform_device *); void (*shutdown)(struct platform_device *); int (*suspend)(struct platform_device *, pm_message_t state); int (*suspend_late)(struct platform_device *, pm_message_t state); int (*resume_early)(struct platform_device *); int (*resume)(struct platform_device *); struct device_driver driver; };
  • 10.
    • Probe 用來偵測特定 Hardware 是否存在,及使用該裝置資源 (clocks 和 device platform_data)
    • 透過底下函式來註冊 Driver
      • int platform_driver_register(struct platform_driver *drv);
    • 過去 Legacy Driver 並不會完全遵守標準 driver model ,這些 driver 會去註冊自己的 platform device ,而不是讓系統來完成註冊
  • 11. 裝置初始化
    • 在大多數的 Platform 設備都必須先註冊 Platform Device
      • 定義 platform_data, resource, 共有多少個 resource 等等
      • platform_device_register
      • platform_add_devices
  • 12. Device Naming 和 Driver Binding
    • platform_device.dev.bus_id 是一個 device id 分為兩個 component:
      • platform_device.name 用來跟 Driver match
      • platform_device.id 裝置編號順序 ( 例如假設有支援多個 NAND 或 NOR Flash) ,如果設定為 -1 表示為獨一無二的裝置
  • 13. Driver binding
    • 在 Driver Core 裡面透過 probe 自動匹對
      • 利用 Device Name and ID 去 match
        • name/id: gpmc_bus.1 或 gpmc_bus
  • 14. board-omap3evm GPMC Device Init Match Driver name GPMC Driver Init GPMC Address IRQ GPMC Clock and Chip Select Define
  • 15. GPMC support functions
    • gpmc_cs_read_reg
    • gpmc_cs_write_reg
    • Please referrer arch/arm/mach-omap2/gpmc.c
  • 16. GPMC Address Mapping
  • 17.
    • Supported Devices
      • .GPMC_CONFIG1_i[11:10]
    • Access Size Adaptation and Device Width
      • .GPMC_CONFIG1_i[13:12]
  • 18. Timing Setting
  • 19. 上面兩張設定如果設定正確,就可以正確看到波形,如果設定錯誤,請準備接收 Kernel Panic
  • 20. 結論
    • Platform Device 和 Platform Driver 區別?
    • GPMC Config_[1-7] 設定方式及規範
    • 實際參考 NAND Driver 程式

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