ALSA: emu10k1: make E-MU FPGA writes potentially more reliable

ossilator · tiwai · commit 15c7e87aa88f · 2024-04-28T11:58:12.000+02:00
We did not delay after the second strobe signal, so another immediately
following access could potentially corrupt the written value.

This is a purely speculative fix with no supporting evidence, but after
taking out the spinlocks around the writes, it seems plausible that a
modern processor could be actually too fast. Also, it's just cleaner to
be consistent.

Signed-off-by: Oswald Buddenhagen &lt;oswald.buddenhagen@gmx.de&gt;
Signed-off-by: Takashi Iwai &lt;tiwai@suse.de&gt;
Message-ID: &lt;20240428093716.3198666-7-oswald.buddenhagen@gmx.de&gt;
diff --git a/sound/pci/emu10k1/io.c b/sound/pci/emu10k1/io.c
@@ -285,6 +285,7 @@ static void snd_emu1010_fpga_write_locked(struct snd_emu10k1 *emu, u32 reg, u32
 	outw(value, emu->port + A_GPIO);
 	udelay(10);
 	outw(value | 0x80 , emu->port + A_GPIO);  /* High bit clocks the value into the fpga. */
+	udelay(10);
 }
 
 void snd_emu1010_fpga_write(struct snd_emu10k1 *emu, u32 reg, u32 value)

Original file line number	Diff line number	Diff line change
`@@ -285,6 +285,7 @@ static void snd_emu1010_fpga_write_locked(struct snd_emu10k1 *emu, u32 reg, u32`
`285`	`285`	`outw(value, emu->port + A_GPIO);`
`286`	`286`	`udelay(10);`
`287`	`287`	`outw(value \| 0x80 , emu->port + A_GPIO); /* High bit clocks the value into the fpga. */`
	`288`	`+ udelay(10);`
`288`	`289`	`}`
`289`	`290`
`290`	`291`	`void snd_emu1010_fpga_write(struct snd_emu10k1 *emu, u32 reg, u32 value)`