ARM IO访问的速度
Depending on the computer platform and bus being used, I/O memory may or may not be accessed through page tables. When access passes though page tables, the kernel must first arrange for the physical address to be visible from your driver, and this usually means that you must call ioremap before doing any I/O. If no page tables are needed, I/O memory locations look pretty much like I/O ports, and ...
by nhjidle - 内核/嵌入技术 - 2006-09-05 14:42:34 阅读（965） 回复（3）
Depending on the computer platform and bus being used, I/O memory may or may not be accessed through page tables. When access passes though page tables, the kernel must first arrange for the physical address to be visible from your driver, and this usually means that you must call ioremap before doing any I/O. If no page tables are needed, I/O memory locations look pretty much like I/O ports, and ...
time dd if=/dev/zero of=ab.dbf bs=8192 count=130000 130000 0 records in 130000 0 records out real 0m48.456s user 0m0.780s sys 0m22.010s 这个REAL，USER，SYS都表示什么意思，如果我算io速度的话，应该怎么算？
Access io before Kernel start 如果要在内核运行之前访问CPU的某些io端口，直接使用指针方式定义寄存器进行操作即可。例如，在解压内核的时候喂狗，通过操作io进行，可以这样操作：在arch/arm/boot/compressed/misc.c文件： 307 arch_decomp_setup(); 308 309 makecrc();[color="#0000FF"] 310 *((volatile unsigned long *)0x40E00054) &= (~(3[color="#0000FF"] 311 *((volatile unsigned long...
io端口 unsigned inb(unsigned port); void outb(unsigned char port, unsigned port); inw inl void insb(unsigned port, void *addr, unsigned long count); void outsb(unsigned port,void *addr,unsigned long count); insw insl io内存 void * ioremap(unsigned long offset, unsigned long size); 返回特殊的虚拟地址，该地址可用来存取特定的物理地址范围 void free(void * addr); unsigned int ioread8(void *addr); unsi...
我得速度如下，cpu是200MHz的arm920T，网卡是smc91c111 百兆 是不是有点低 C:\win32-i386 -t 192.168.68.221 NETio - Network Throughput Benchmark, Version 1.26 (C) 1997-2005 Kai Uwe Rommel TCP connection established. Packet size 1k bytes: 173 KByte/s Tx, 2911 KByte/s Rx. Packet size 2k bytes: 1788 KByte/s Tx, 2652 KByte/s Rx. Packet size 4k bytes: 1082 KByte/s Tx, 3841 KByte/s Rx. Packet size...
设计了一个arm的usb驱动．可是，能够运用．但是速度很慢，不知从何改写． 请问一下大侠，能不能提供一些解决方案． 如果需要源代码，请发email给我．谢谢.supervisorxuxiaodong@126.com
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今天在arm上面试验io操作，碰到的一个问题可以提出来备忘。一般而言，内核提供的io操作函数集有如：ioread,ioread16，ioread32,iowrite32这些函数等等一般是“提倡”使用的，而不提倡直接对ioremap返回的值进行操作。所以今天我在BE的arm上使用iowrite32和ioread32这两个函数来操作，得到的结果十分诡异，令我迷惑了很久。后来上内核源码中一看，居然看到了： #define ioread32 ( p ) ({ unsigned int __v = le32_to_cpu...
