Re: [PATCH] ASoC: pxa: remove incorrect do_div() call

From: zhangfei
Date: Mon Nov 23 2015 - 03:11:04 EST

On 11/20/2015 05:32 PM, Arnd Bergmann wrote:
The new optimized do_div implementation (now in asm-generic/next) exposes a
glitch in the brownstone audio driver by producing a compile-time warning:

sound/soc/pxa/brownstone.c: In function 'brownstone_wm8994_hw_params':
sound/soc/pxa/brownstone.c:67:85: warning: comparison of distinct pointer types lacks a cast
sound/soc/pxa/brownstone.c:67:10125: warning: right shift count >= width of type [-Wshift-count-overflow]
sound/soc/pxa/brownstone.c:67:10254: warning: passing argument 1 of '__div64_32' from incompatible pointer type [-Wincompatible-pointer-types]

The driver just divides two plain integer values, so it should not
use do_div to start with, but has apparently done so ever since the
code was first merged. This replaces do_div with a simple division

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
I think this one is harmless, so we only need it in 4.5 to avoid the warning,
but not backported to earlier kernels.

Found today on ARM allmodconfig

diff --git a/sound/soc/pxa/brownstone.c b/sound/soc/pxa/brownstone.c
index 6147e86e9b0f..416ea646c3b1 100644
--- a/sound/soc/pxa/brownstone.c
+++ b/sound/soc/pxa/brownstone.c
@@ -63,8 +63,7 @@ static int brownstone_wm8994_hw_params(struct snd_pcm_substream *substream,
sysclk = params_rate(params) * 512;
sspa_mclk = params_rate(params) * 64;
- sspa_div = freq_out;
- do_div(sspa_div, sspa_mclk);
+ sspa_div = freq_out / sspa_mclk;

snd_soc_dai_set_sysclk(cpu_dai, MMP_SSPA_CLK_AUDIO, freq_out, 0);
snd_soc_dai_set_pll(cpu_dai, MMP_SYSCLK, 0, freq_out, sysclk);

Thanks Arnd.

Looks sspa_div is not used at all.
So we can remove sspa_div as well as do_div.

What do you think.


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