RK11: write protect action too slow

[wfjm]

Some simple RK11 drivers, especially in test codes, don't poll for completion of a write protect command. Due to the emulated I/O this can cause errors.

One example is the boot sequence of RK based XXDP, as seen for example for the dzzza disk. On simh the disk is immediately switched to write protect mode, on w11 it is not. The pertinent part of the code is

    000214  B003:  mov	#000017,@#rk.cs   ; #rk.fwl+rk.go;  func=write_lock
    000222         bic	#017777,r2      
    000226         clc	
    000230         rol	r2
    000232         rol	r2
    000234         rol	r2
    000236         rol	r2
    000240         mov	r2,D040
    000244         mov	#000001,@#rk.cs   ; #rk.go;         func=control reset

The monitor does two writes to the RK11 CSR without busy polling and just a few instructions in between. In the w11 implementation the first write will set func=write_lock and cause an attn request. But before the attn can be serviced the CSR is overwritten with func=creset. The write lock is lost, only the creset is executed.

Can be resolved by handling write lock locally. Normal OS always do a busy poll before starting a function, therefore this is considered a minor deficit. Might be fixed in an upcoming release.

originally filed as issue w11a_V0.50-2 and TCK-025 dated 2008-05-03.