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ALSA: emu10k1: simplify snd_emu10k1_audigy_dsp_convert_32_to_2x16()

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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@gmx.de>
Link: https://lore.kernel.org/r/20230510173917.3073107-5-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Oswald Buddenhagen
2023-05-10 19:39:07 +02:00
committed by Takashi Iwai
parent 4102ac2975
commit 4c7bfbcf75
1 changed files with 13 additions and 13 deletions
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26
sound/pci/emu10k1/emufx.c
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@@ -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)