ASoC: Intel: bytcr_rt5640: fallback mechanism if MCLK is not enabled

Commit df1a2776a795 ("ASoC: Intel: bytcr_rt5640: add MCLK support")
was merged but the corresponding clock framework patches have not,
after being bumped from audio to clock to x86 domains. The missing
clock-related patches result in a regression starting with 4.9 with
the audio card not being created.

Rather than reverting this commit and all following updates already
queued up for 4.10, handle run-time dependency on MCLK and fall back
to the previous bit-clock mode. This provides the same functionality
as in 4.8 for Baytrail devices. On Baytrail-CR most devices remain
silent with this fallback but additional patches are needed anyway.
As suggested by Mark Brown, the fallback is only allowed with -ENOENT,
all other run-time errors, including -EPROBE_DEFER, will stop the probe
with no sound card registered.

This patch should be applied to -stable as well as ASoC 4.10 fixes

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/sound/soc/intel/boards/bytcr_rt5640.c b/sound/soc/intel/boards/bytcr_rt5640.c
index 507a86a5eafe5646bb9731f865b85571eb6ffdfc..e33e4777a65c3fce2505f75b8fd756a3450e96b5 100644 (file)
--- a/sound/soc/intel/boards/bytcr_rt5640.c
+++ b/sound/soc/intel/boards/bytcr_rt5640.c
@@ -825,10 +825,20 @@ static int snd_byt_rt5640_mc_probe(struct platform_device *pdev)
        if ((byt_rt5640_quirk & BYT_RT5640_MCLK_EN) && (is_valleyview())) {
                priv->mclk = devm_clk_get(&pdev->dev, "pmc_plt_clk_3");
                if (IS_ERR(priv->mclk)) {
+                       ret_val = PTR_ERR(priv->mclk);
+
                        dev_err(&pdev->dev,
-                               "Failed to get MCLK from pmc_plt_clk_3: %ld\n",
-                               PTR_ERR(priv->mclk));
-                       return PTR_ERR(priv->mclk);
+                               "Failed to get MCLK from pmc_plt_clk_3: %d\n",
+                               ret_val);
+
+                       /*
+                        * Fall back to bit clock usage for -ENOENT (clock not
+                        * available likely due to missing dependencies), bail
+                        * for all other errors, including -EPROBE_DEFER
+                        */
+                       if (ret_val != -ENOENT)
+                               return ret_val;
+                       byt_rt5640_quirk &= ~BYT_RT5640_MCLK_EN;
                }
        }