linux-kernel - [PATCH 2/2] sound: ad1889: Replace mdelay with usleep_range in snd_ad1889_ac97

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Date:   Mon,  9 Apr 2018 21:03:38 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     T-Bone@...isc-linux.org, perex@...ex.cz, tiwai@...e.com
Cc:     linux-parisc@...r.kernel.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH 2/2] sound: ad1889: Replace mdelay with usleep_range in snd_ad1889_ac97_ready

snd_ad1889_ac97_ready() is never called in atomic context.

The call chain ending up at snd_ad1889_ac97_ready() is:
[1] snd_ad1889_ac97_ready() <- snd_ad1889_ac97_xinit() <- 
	snd_ad1889_ac97_init() <- snd_ad1889_probe()

snd_ad1889_probe() is only set as ".probe" in struct pci_driver.
This function is not called in atomic context.

Despite never getting called from atomic context, snd_ad1889_ac97_ready()
calls mdelay for busy wait.
This is not necessary and can be replaced with usleep_range to
avoid busy waiting.

This is found by a static analysis tool named DCNS written by myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 sound/pci/ad1889.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/pci/ad1889.c b/sound/pci/ad1889.c
index 0bf2c04..a2a8e1d 100644
--- a/sound/pci/ad1889.c
+++ b/sound/pci/ad1889.c
@@ -258,7 +258,7 @@ struct snd_ad1889 {
 	
 	while (!(ad1889_readw(chip, AD_AC97_ACIC) & AD_AC97_ACIC_ACRDY) 
 			&& --retry)
-		mdelay(1);
+		usleep_range(1000, 2000);
 	if (!retry) {
 		dev_err(chip->card->dev, "[%s] Link is not ready.\n",
 			__func__);
-- 
1.9.1