ALSA: emu10k1: fix+optimize E-MU stereo capture DSP code

Presumably, JDC added the seemingly superfluous indirection over the
temporary register because without it he'd get only zero readings.
However, switching the X and Y operands (or using EMU32 as the A
operand in the temporary load) works just fine. Presumably a DSP bug?

The original code was also actually buggy, though: both channels used
the left volume control.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230510173917.3073107-4-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/pci/emu10k1/emufx.c b/sound/pci/emu10k1/emufx.c
index eb40159..795b257 100644 (file)
--- a/sound/pci/emu10k1/emufx.c
+++ b/sound/pci/emu10k1/emufx.c
@@ -1324,11 +1324,9 @@ A_OP(icode, &ptr, iMAC0, A_GPR(var), A_GPR(var), A_GPR(vol), A_EXTIN(input))
                /* EMU1010 DSP 0 and DSP 1 Capture */
                // The 24 MSB hold the actual value. We implicitly discard the 16 LSB.
                if (emu->card_capabilities->ca0108_chip) {
-                       /* Note:JCD:No longer bit shift lower 16bits to upper 16bits of 32bit value. */
-                       A_OP(icode, &ptr, iMACINT0, A_GPR(tmp), A_C_00000000, A3_EMU32IN(0x0), A_C_00000001);
-                       A_OP(icode, &ptr, iMAC0, A_GPR(capture+0), A_GPR(capture+0), A_GPR(gpr), A_GPR(tmp));
-                       A_OP(icode, &ptr, iMACINT0, A_GPR(tmp), A_C_00000000, A3_EMU32IN(0x1), A_C_00000001);
-                       A_OP(icode, &ptr, iMAC0, A_GPR(capture+1), A_GPR(capture+1), A_GPR(gpr), A_GPR(tmp));
+                       // For unclear reasons, the EMU32IN cannot be the Y operand!
+                       A_OP(icode, &ptr, iMAC0, A_GPR(capture+0), A_GPR(capture+0), A3_EMU32IN(0x0), A_GPR(gpr));
+                       A_OP(icode, &ptr, iMAC0, A_GPR(capture+1), A_GPR(capture+1), A3_EMU32IN(0x1), A_GPR(gpr+1));
                } else {
                        A_OP(icode, &ptr, iMAC0, A_GPR(capture+0), A_GPR(capture+0), A_GPR(gpr), A_P16VIN(0x0));
                        A_OP(icode, &ptr, iMAC0, A_GPR(capture+1), A_GPR(capture+1), A_GPR(gpr+1), A_P16VIN(0x1));