linux-kernel - [PATCH 1/2] sound: ad1889: Replace mdelay with usleep_range in snd_ad1889

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Date:   Mon,  9 Apr 2018 21:03:20 +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 1/2] sound: ad1889: Replace mdelay with usleep_range in snd_ad1889_init

snd_ad1889_init() is never called in atomic context.

The call chain ending up at snd_ad1889_init() is:
[1] snd_ad1889_init() <- snd_ad1889_create() <- 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_init()
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..d4965eb 100644
--- a/sound/pci/ad1889.c
+++ b/sound/pci/ad1889.c
@@ -872,7 +872,7 @@ struct snd_ad1889 {
 	ad1889_writew(chip, AD_DS_CCS, AD_DS_CCS_CLKEN); /* turn on clock */
 	ad1889_readw(chip, AD_DS_CCS);	/* flush posted write */
 
-	mdelay(10);
+	usleep_range(10000, 11000);
 
 	/* enable Master and Target abort interrupts */
 	ad1889_writel(chip, AD_DMA_DISR, AD_DMA_DISR_PMAE | AD_DMA_DISR_PTAE);
-- 
1.9.1