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m68k/mac: Make SCC reset work more reliably

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For SCC initialization we cannot assume that the control register is in
the correct state to accept a register pointer. So first read from the
control register in order to "sync" up.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
This commit is contained in:
Finn Thain 2014-01-13 00:56:38 +11:00 committed by Geert Uytterhoeven
parent a0b7b24226
commit 56931d7369
1 changed files with 3 additions and 1 deletions
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4
arch/m68k/kernel/head.S
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@ -2915,7 +2915,9 @@ func_start serial_init,%d0/%d1/%a0/%a1
#if defined(MAC_USE_SCC_A) || defined(MAC_USE_SCC_B)
movel %pc@(L(mac_sccbase)),%a0
/* Reset SCC device */
/* Reset SCC register pointer */
moveb %a0@(mac_scc_cha_a_ctrl_offset),%d0
/* Reset SCC device: write register pointer then register value */
moveb #9,%a0@(mac_scc_cha_a_ctrl_offset)
moveb #0xc0,%a0@(mac_scc_cha_a_ctrl_offset)
/* Wait for 5 PCLK cycles, which is about 68 CPU cycles */