Linux-4.9.2内核在mini2440上的移植(八)——RTC驱动移植
本篇目标：移植RTC驱动，使时钟正常运行。
8.1 添加RTC支持
上篇说到，RTC的驱动有问题，这个问题在启动日志中的体现是hctosys: unable to open rtc device (rtc0)，可见RTC驱动没有加载上。
我们先将RTC驱动添加到mach-mini2440.c文件中。
root@ubuntu:~/linux-4.9.2#vim arch/arm/mach-s3c24xx/mach-mini2440.c
到251行附近：
static structplatform_device *mini2440_devices[] __initdata = {
&s3c_device_ohci,
&s3c_device_lcd,
&s3c_device_wdt,
&s3c_device_i2c0,
&s3c_device_iis,
&s3c_device_nand,
&s3c_device_rtc,
&mini2440_device_eth,
};
添加即可
8.2在内核中配置RTC
接下来重新配置内核，以加入RTC的驱动支持，依次选择如下菜单项：
DeviceDrivers --->
< *> Real Time Clock --->
<*> Samsung S3C series SoC RTC //这里才是内核中真正的2440之RTC 驱动配置项。
确认完毕后，退出。
8.3 编译测试
root@ubuntu:~/linux-4.9.2#make -j8
root@ubuntu:~/linux-4.9.2#./mkuImage.sh
重启开发板
问题依旧
8.4 原因分析
经过网上大量查阅资料，网上给出的答案都无法完美解决此问题，笔者怀疑是驱动不匹配。
经过笔者大量linux内核版本测试，发现RTC有效的最后的版本是linux-3.17.8版本，升级到linux3.18.2版本的时候RTC驱动就无效了。这可能是版本升级的时候的bug，也许是新的驱动不会用？
8.5具体操作如下
（1）下载linux-3.17.8源码
root@ubuntu:~/linux-4.9.2#cd /root/
root@ubuntu:~#wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.17.8.tar.gz
（2）解压
root@ubuntu:~#tar -zxvf linux-3.17.8.tar.gz
（3）备份
root@ubuntu:~#cp linux-4.9.2/drivers/rtc/rtc-s3c.c linux-4.9.2/drivers/rtc/rtc-s3c_backup.c
（4）替换驱动
cplinux-3.17.8/drivers/rtc/rtc-s3c.c linux-4.9.2/drivers/rtc/
（5）编译
root@ubuntu:~#cd linux-4.9.2/
root@ubuntu:~/linux-4.9.2#make -j8
root@ubuntu:~/linux-4.9.2#./mkuImage.sh
（6）重启开发板
Starting kernel...
Booting Linux onphysical CPU 0x0
Linux version4.9.2 (root@ubuntu) (gcc version 6.3.0 20170406 (Ubuntu/Linaro 6.3.0-12ubuntu2)) #12 Wed Sep 27 22:39:58 PDT 2017
CPU: ARM920T[41129200] revision 0 (ARMv4T), cr=c000717f
CPU: VIVT datacache, VIVT instruction cache
Machine:Mini2440 development board
Memory policy:Data cache writeback
CPU S3C2440A (id0x32440001)
Built 1zonelists in Zone order, mobility grouping on. Total pages: 16256
Kernel commandline: console=ttySAC0,115200 root=/dev/nfsnfsroot=192.168.2.104:/root/NFS/rootfsip=192.168.2.188:192.168.2.104:192.168.2.1:255.255.255.0:SMDK2440A.arm9.net:eth0:offinit=/linuxrc
PID hash tableentries: 256 (order: -2, 1024 bytes)
Dentry cachehash table entries: 8192 (order: 3, 32768 bytes)
Inode-cache hashtable entries: 4096 (order: 2, 16384 bytes)
Memory:58756K/65536K available (4379K kernel code, 177K rwdata, 996K rodata, 176Kinit, 259K bss, 6780K reserved, 0K cma-reserved)
Virtual kernelmemory layout:
vector : 0xffff0000 - 0xffff1000 ( 4 kB)
fixmap : 0xffc00000 - 0xfff00000 (3072kB)
vmalloc : 0xc4800000 - 0xff800000 ( 944 MB)
lowmem : 0xc0000000 - 0xc4000000 ( 64 MB)
modules : 0xbf000000 - 0xc0000000 ( 16MB)
.text : 0xc0008000 - 0xc044efd0 (4380 kB)
.init : 0xc0568000 - 0xc0594000 ( 176 kB)
.data : 0xc0594000 - 0xc05c07c0 ( 178 kB)
.bss : 0xc05c07c0 - 0xc0601400 ( 260 kB)
SLUB:HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
NR_IRQS:103
S3C2440: IRQSupport
irq: clearingpending status 00000002
sched_clock: 16bits at 1012kHz, resolution 987ns, wraps every 32362962ns
clocksource:samsung_clocksource_timer: mask: 0xffff max_cycles: 0xffff, max_idle_ns:28803037 ns
Console: colourdummy device 80x30
Calibratingdelay loop... 201.52 BogoMIPS (lpj=503808)
pid_max:default: 32768 minimum: 301
Mount-cache hashtable entries: 1024 (order: 0, 4096 bytes)
Mountpoint-cachehash table entries: 1024 (order: 0, 4096 bytes)
CPU: Testingwrite buffer coherency: ok
Setting upstatic identity map for 0x300081e0 - 0x30008238
clocksource:jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 9556302231375000ns
NET: Registeredprotocol family 16
DMA:preallocated 256 KiB pool for atomic coherent allocations
cpuidle: usinggovernor ladder
S3C2440:Initialising architecture
usbcore:registered new interface driver usbfs
usbcore:registered new interface driver hub
usbcore:registered new device driver usb
s3c-i2cs3c2440-i2c.0: slave address 0x10
s3c-i2cs3c2440-i2c.0: bus frequency set to 98 KHz
s3c-i2cs3c2440-i2c.0: i2c-0: S3C I2C adapter
Advanced LinuxSound Architecture Driver Initialized.
clocksource:Switched to clocksource samsung_clocksource_timer
NET: Registeredprotocol family 2
TCP establishedhash table entries: 1024 (order: 0, 4096 bytes)
TCP bind hashtable entries: 1024 (order: 0, 4096 bytes)
TCP: Hash tablesconfigured (established 1024 bind 1024)
UDP hash tableentries: 256 (order: 0, 4096 bytes)
UDP-Lite hashtable entries: 256 (order: 0, 4096 bytes)
NET: Registeredprotocol family 1
RPC: Registerednamed UNIX socket transport module.
RPC: Registeredudp transport module.
RPC: Registeredtcp transport module.
RPC: Registeredtcp NFSv4.1 backchannel transport module.
futex hash tableentries: 256 (order: -1, 3072 bytes)
workingset:timestamp_bits=30 max_order=14 bucket_order=0
NFS: Registeringthe id_resolver key type
Key typeid_resolver registered
Key typeid_legacy registered
jffs2: version2.2. (NAND) © 2001-2006 Red Hat, Inc.
romfs: ROMFS MTD(C) 2007 Red Hat, Inc.
io schedulernoop registered
io schedulerdeadline registered
io scheduler cfqregistered (default)
Console:switching to colour frame buffer device 60x53
s3c2410-lcds3c2410-lcd: fb0: s3c2410fb frame buffer device
s3c2440-uart.0:ttySAC0 at MMIO 0x50000000 (irq = 74, base_baud = 0) is a S3C2440
console[ttySAC0] enabled
s3c2440-uart.1:ttySAC1 at MMIO 0x50004000 (irq = 77, base_baud = 0) is a S3C2440
s3c2440-uart.2:ttySAC2 at MMIO 0x50008000 (irq = 80, base_baud = 0) is a S3C2440
brd: moduleloaded
s3c24xx-nands3c2440-nand: Tacls=3, 29ns Twrph0=7 69ns, Twrph1=3 29ns
s3c24xx-nands3c2440-nand: NAND soft ECC
nand: devicefound, Manufacturer ID: 0xec, Chip ID: 0xda
nand: SamsungNAND 256MiB 3,3V 8-bit
nand: 256 MiB,SLC, erase size: 128 KiB, page size: 2048, OOB size: 64
Scanning devicefor bad blocks
Bad eraseblock1620 at 0x00000ca80000
Bad eraseblock1935 at 0x00000f1e0000
Creating 5 MTDpartitions on "NAND":
0x000000000000-0x000000040000: "boot"
0x000000040000-0x000000060000: "param"
0x000000060000-0x000000560000: "kernel"
0x000000560000-0x000006960000: "rootfs"
0x000000000000-0x000010000000: "nand"
eth0: dm9000e atc4a5b300,c4a5d304 IRQ 55 MAC: 08:00:3e:26:0a:5b (chip)
ohci_hcd: USB1.1 'Open' Host Controller (OHCI) Driver
ohci-s3c2410:OHCI S3C2410 driver
s3c2410-ohcis3c2410-ohci: OHCI Host Controller
s3c2410-ohcis3c2410-ohci: new USB bus registered, assigned bus number 1
s3c2410-ohcis3c2410-ohci: irq 42, io mem 0x49000000
random: fastinit done
hub 1-0:1.0: USBhub found
hub 1-0:1.0: 2ports detected
mousedev: PS/2mouse device common for all mice
s3c-rtcs3c2410-rtc: rtc disabled, re-enabling
s3c-rtcs3c2410-rtc: rtc core: registered s3c as rtc0
i2c /dev entriesdriver
s3c2410-wdts3c2410-wdt: watchdog inactive, reset disabled, irq disabled
sdhci: SecureDigital Host Controller Interface driver
sdhci:Copyright(c) Pierre Ossman
hidraw: raw HIDevents driver (C) Jiri Kosina
usbcore:registered new interface driver usbhid
usbhid: USB HIDcore driver
NET: Registeredprotocol family 17
Key typedns_resolver registered
s3c-rtc s3c2410-rtc: setting system clock to 2017-09-2813:55:16 UTC (1506606916)
dm9000 dm9000eth0: link down
dm9000 dm9000eth0: link up, 100Mbps, full-duplex, lpa 0x45E1
IP-Config:Complete:
device=eth0, hwaddr=08:00:3e:26:0a:5b,ipaddr=192.168.2.188, mask=255.255.255.0, gw=192.168.2.1
host=SMDK2440A, domain=, nis-domain=arm9.net
bootserver=192.168.2.104,rootserver=192.168.2.104, rootpath=
ALSA devicelist:
No soundcards found.
VFS: Mountedroot (nfs filesystem) on device 0:12.
Freeing unusedkernel memory: 176K (c0568000 - c0594000)
Thisarchitecture does not have kernel memory protection.
mount: mountingnone on /proc/bus/usb failed: No such file or directory
/etc/init.d/rcS:line 39: /etc/rc.d/init.d/netd: Input/output error
/etc/init.d/rcS:line 43: /etc/rc.d/init.d/httpd: Input/output error
/etc/init.d/rcS:line 47: /etc/rc.d/init.d/leds: Input/output error
Please pressEnter to activate this console. /bin/qtopia: line 22: can't create/etc/pointercal: Permission denied
random: crnginit done
可以看到RTC已经正常运行了
在secureCRT按回车，输入hwclock
[root@FriendlyARM/]# hwclock
Thu Sep 2813:58:13 2017 0.000000 seconds
没问题。
新版的RTC驱动应该是需要修改才能用，可以对比一下drivers/rtc/rtc-s3c.c在linux4.9.2与linux3.17.8这两个版本有什么不同，应该就是需要修改的关键了。