Hi Finn,
On Mon, Mar 3, 2014 at 12:56 PM, Finn Thain <[email protected]> wrote: > Fix SCC initialization for Atari as was previously fixed for Mac. It's > probably not practical to share more code but some attempt is made to > align the Mac and Atari variants. > > --- > One problem with this patch is that it fixes a problem that doesn't affect > anyone (as long as Atari SCC debugging remains disabled). > > The line rate is changed to 38400 baud to match the Mac code (which > follows the pmac_zilog serial console default). It would be nice to > standardize but I don't know whether this is realistic. > > The 7.9872 MHz PCLK used in this patch was inferred from the existing code > as I don't have any hardware data. The difference in clock source settings is the main reason we can't use the exact same code IIRC. > This patch is untested on Atari. I can do that - good excuse to reenable the SCC debugging anyway. Cheers, Michael > > --- > arch/m68k/kernel/head.S | 34 ++++++++++++++++++++++------------ > 1 file changed, 22 insertions(+), 12 deletions(-) > > Index: linux-m68k/arch/m68k/kernel/head.S > =================================================================== > --- linux-m68k.orig/arch/m68k/kernel/head.S 2014-03-03 10:30:01.000000000 > +1100 > +++ linux-m68k/arch/m68k/kernel/head.S 2014-03-03 10:30:32.000000000 +1100 > @@ -2722,6 +2722,7 @@ func_return get_new_page > #define MAC_USE_SCC_B /* Printer port */ > > #if defined(MAC_USE_SCC_A) || defined(MAC_USE_SCC_B) > +/* Initialisation table for SCC with 3.6864 MHz PCLK */ > L(scc_initable_mac): > .byte 4,0x44 /* x16, 1 stopbit, no parity */ > .byte 3,0xc0 /* receiver: 8 bpc */ > @@ -2744,17 +2745,14 @@ L(scc_initable_mac): > #define USE_MFP > > #if defined(USE_SCC_A) || defined(USE_SCC_B) > -#define USE_SCC > -/* Initialisation table for SCC */ > -L(scc_initable): > - .byte 9,12 /* Reset */ > - .byte 4,0x44 /* x16, 1 stopbit, no parity */ > +/* Initialisation table for SCC with 7.9872 MHz PCLK */ > +L(scc_initable_atari): > + .byte 4,0x04 /* x1, 1 stopbit, no parity */ > .byte 3,0xc0 /* receiver: 8 bpc */ > .byte 5,0xe2 /* transmitter: 8 bpc, assert dtr/rts */ > - .byte 9,0 /* no interrupts */ > .byte 10,0 /* NRZ */ > .byte 11,0x50 /* use baud rate generator */ > - .byte 12,24,13,0 /* 9600 baud */ > + .byte 12,102,13,0 /* 38400 baud */ > .byte 14,2,14,3 /* use master clock for BRG, enable */ > .byte 3,0xc1 /* enable receiver */ > .byte 5,0xea /* enable transmitter */ > @@ -2800,7 +2798,7 @@ LMFP_UDR = 0xfffa2f > */ > > /* > - * Initialize serial port hardware for 9600/8/1 > + * Initialize serial port hardware > */ > func_start serial_init,%d0/%d1/%a0/%a1 > /* > @@ -2810,7 +2808,7 @@ func_start serial_init,%d0/%d1/%a0/%a1 > * d0 = boot info offset > * CONFIG_ATARI > * a0 = address of SCC > - * a1 = Liobase address/address of scc_initable > + * a1 = Liobase address/address of scc_initable_atari > * d0 = init data for serial port > * CONFIG_MAC > * a0 = address of SCC > @@ -2846,9 +2844,21 @@ func_start serial_init,%d0/%d1/%a0/%a1 > moveb %a1@(LPSG_READ),%d0 > bset #5,%d0 > moveb %d0,%a1@(LPSG_WRITE) > -#elif defined(USE_SCC) > +#elif defined(USE_SCC_A) || defined(USE_SCC_B) > lea %a1@(LSCC_CTRL),%a0 > - lea %pc@(L(scc_initable)),%a1 > + /* Reset SCC register pointer */ > + moveb %a0@,%d0 > + /* Reset SCC device: write register pointer then register value */ > + moveb #9,%a0@ > + moveb #0xc0,%a0@ > + /* Wait for 5 PCLK cycles, which is about 63 CPU cycles */ > + /* 5 / 7.9872 MHz = approx. 0.63 us = 63 / 100 MHz */ > + movel #32,%d0 > +2: > + subq #1,%d0 > + jne 2b > + /* Initialize channel */ > + lea %pc@(L(scc_initable_atari)),%a1 > 2: moveb %a1@+,%d0 > jmi 3f > moveb %d0,%a0@ > @@ -3017,7 +3027,7 @@ func_start serial_putc,%d0/%d1/%a0/%a1 > nop > bset #5,%d0 > moveb %d0,%a1@(LPSG_WRITE) > -#elif defined(USE_SCC) > +#elif defined(USE_SCC_A) || defined(USE_SCC_B) > 3: btst #2,%a1@(LSCC_CTRL) > jeq 3b > moveb %d0,%a1@(LSCC_DATA) > -- > To unsubscribe from this list: send the line "unsubscribe linux-m68k" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-m68k" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
