Instead of spending lots of instructions on masking and transplanting
the sign bit, sidestep the issue by replacing the last bit shift with
a wrapping addition to self.
Solution stolen from kX-project, after I pondered other ideas first.
Also, the function really doesn't need to return a constant int value.
Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@xxxxxx>
---
sound/pci/emu10k1/emufx.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/sound/pci/emu10k1/emufx.c b/sound/pci/emu10k1/emufx.c
index 795b2573fef4..8ba294138dfe 100644
--- a/sound/pci/emu10k1/emufx.c
+++ b/sound/pci/emu10k1/emufx.c
@@ -1184,20 +1184,22 @@ snd_emu10k1_init_stereo_onoff_control(struct snd_emu10k1_fx8010_control_gpr *ctl
* to 2 x 16-bit registers in Audigy - their values are read via DMA.
* Conversion is performed by Audigy DSP instructions of FX8010.
*/
-static int snd_emu10k1_audigy_dsp_convert_32_to_2x16(
+static void snd_emu10k1_audigy_dsp_convert_32_to_2x16(
struct snd_emu10k1_fx8010_code *icode,
u32 *ptr, int tmp, int bit_shifter16,
int reg_in, int reg_out)
{
- A_OP(icode, ptr, iACC3, A_GPR(tmp + 1), reg_in, A_C_00000000, A_C_00000000);
- A_OP(icode, ptr, iANDXOR, A_GPR(tmp), A_GPR(tmp + 1), A_GPR(bit_shifter16 - 1), A_C_00000000);
- A_OP(icode, ptr, iTSTNEG, A_GPR(tmp + 2), A_GPR(tmp), A_C_80000000, A_GPR(bit_shifter16 - 2));
- A_OP(icode, ptr, iANDXOR, A_GPR(tmp + 2), A_GPR(tmp + 2), A_C_80000000, A_C_00000000);
- A_OP(icode, ptr, iANDXOR, A_GPR(tmp), A_GPR(tmp), A_GPR(bit_shifter16 - 3), A_C_00000000);
- A_OP(icode, ptr, iMACINT0, A_GPR(tmp), A_C_00000000, A_GPR(tmp), A_C_00010000);
- A_OP(icode, ptr, iANDXOR, reg_out, A_GPR(tmp), A_C_ffffffff, A_GPR(tmp + 2));
- A_OP(icode, ptr, iACC3, reg_out + 1, A_GPR(tmp + 1), A_C_00000000, A_C_00000000);
- return 1;
+ // This leaves the low word in place, which is fine,
+ // as the low bits are completely ignored subsequently.
+ // reg_out[1] = reg_in
+ A_OP(icode, ptr, iACC3, reg_out + 1, reg_in, A_C_00000000, A_C_00000000);
+ // It is fine to read reg_in multiple times.
+ // tmp = reg_in << 15
+ A_OP(icode, ptr, iMACINT1, A_GPR(tmp), A_C_00000000, reg_in, A_GPR(bit_shifter16));
+ // Left-shift once more. This is a separate step, as the
+ // signed multiplication would clobber the MSB.
+ // reg_out[0] = tmp + ((tmp << 31) >> 31)
+ A_OP(icode, ptr, iMAC3, reg_out, A_GPR(tmp), A_GPR(tmp), A_C_80000000);
}
/*
@@ -1247,10 +1249,8 @@ static int _snd_emu10k1_audigy_init_efx(struct snd_emu10k1 *emu)
ptr = 0;
nctl = 0;
gpr = stereo_mix + 10;
- gpr_map[gpr++] = 0x00007fff;
- gpr_map[gpr++] = 0x00008000;
- gpr_map[gpr++] = 0x0000ffff;
bit_shifter16 = gpr;
+ gpr_map[gpr++] = 0x00008000;
#if 1
/* PCM front Playback Volume (independent from stereo mix)
--
2.40.0.152.g15d061e6df
