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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Takashi Iwai <tiwai@suse.de>
Subject: [PATCH 4.9 138/175] ALSA: usb-audio: Disable sample read check if firmware doesnt give back
Date:   Mon, 28 Dec 2020 13:49:51 +0100
Message-Id: <20201228124859.934142007@linuxfoundation.org>
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References: <20201228124853.216621466@linuxfoundation.org>
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From: Takashi Iwai <tiwai@suse.de>

commit 9df28edce7c6ab38050235f6f8b43dd7ccd01b6d upstream.

Some buggy firmware don't give the current sample rate but leaves
zero.  Handle this case more gracefully without warning but just skip
the current rate verification from the next time.

Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201218145858.2357-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/usb/clock.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/sound/usb/clock.c
+++ b/sound/usb/clock.c
@@ -327,6 +327,12 @@ static int set_sample_rate_v1(struct snd
 	}
 
 	crate = data[0] | (data[1] << 8) | (data[2] << 16);
+	if (!crate) {
+		dev_info(&dev->dev, "failed to read current rate; disabling the check\n");
+		chip->sample_rate_read_error = 3; /* three strikes, see above */
+		return 0;
+	}
+
 	if (crate != rate) {
 		dev_warn(&dev->dev, "current rate %d is different from the runtime rate %d\n", crate, rate);
 		// runtime->rate = crate;