linux-kernel - [PATCH AUTOSEL 6.6 20/43] ALSA: emu10k1: make E-MU FPGA writes potentially more reliable

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Message-ID: <20240507231033.393285-20-sashal@kernel.org>
Date: Tue,  7 May 2024 19:09:41 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Oswald Buddenhagen <oswald.buddenhagen@....de>,
	Takashi Iwai <tiwai@...e.de>,
	Sasha Levin <sashal@...nel.org>,
	perex@...ex.cz,
	tiwai@...e.com,
	linux-sound@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 20/43] ALSA: emu10k1: make E-MU FPGA writes potentially more reliable

From: Oswald Buddenhagen <oswald.buddenhagen@....de>

[ Upstream commit 15c7e87aa88f0ab2d51c2e2123b127a6d693ca21 ]

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 <oswald.buddenhagen@....de>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Message-ID: <20240428093716.3198666-7-oswald.buddenhagen@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/pci/emu10k1/io.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sound/pci/emu10k1/io.c b/sound/pci/emu10k1/io.c
index 74df2330015f6..5cb8acf5b158c 100644
--- 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)
-- 
2.43.0