ASoC: tegra: ahub: Reset hardware properly

Assert hardware resets before clocks are enabled and then de-assert them
after clocks are enabled. This brings hardware into a predictable state.

Tested-by: Peter Geis <pgwipeout@gmail.com> # Ouya T30 audio works
Tested-by: Matt Merhar <mattmerhar@protonmail.com> # Ouya T30 boot-tested
Tested-by: Dmitry Osipenko <digetx@gmail.com> # Nexus7 T30 audio works
Tested-by: Nicolas Chauvet <kwizart@gmail.com> # TK1 boot-tested
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20210120003154.26749-7-digetx@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/tegra/tegra30_ahub.c

@@ -65,14 +65,39 @@ static int tegra30_ahub_runtime_resume(struct device *dev)
 {
 	int ret;
 
+	ret = reset_control_assert(ahub->reset);
+	if (ret)
+		return ret;
+
 	ret = clk_bulk_prepare_enable(ahub->nclocks, ahub->clocks);
 	if (ret)
 		return ret;
 
+	usleep_range(10, 100);
+
+	ret = reset_control_deassert(ahub->reset);
+	if (ret)
+		goto disable_clocks;
+
 	regcache_cache_only(ahub->regmap_apbif, false);
 	regcache_cache_only(ahub->regmap_ahub, false);
+	regcache_mark_dirty(ahub->regmap_apbif);
+	regcache_mark_dirty(ahub->regmap_ahub);
+
+	ret = regcache_sync(ahub->regmap_apbif);
+	if (ret)
+		goto disable_clocks;
+
+	ret = regcache_sync(ahub->regmap_ahub);
+	if (ret)
+		goto disable_clocks;
 
 	return 0;
+
+disable_clocks:
+	clk_bulk_disable_unprepare(ahub->nclocks, ahub->clocks);
+
+	return ret;
 }
 
 int tegra30_ahub_allocate_rx_fifo(enum tegra30_ahub_rxcif *rxcif,
@@ -519,7 +544,6 @@ static int tegra30_ahub_probe(struct platform_device *pdev)
 	/*
 	 * The AHUB hosts a register bus: the "configlink". For this to
 	 * operate correctly, all devices on this bus must be out of reset.
-	 * Ensure that here.
 	 */
 	for (i = 0; i < ARRAY_SIZE(configlink_mods); i++) {
 		if (!(configlink_mods[i].mod_list_mask &
@@ -535,10 +559,8 @@ static int tegra30_ahub_probe(struct platform_device *pdev)
 			return ret;
 		}
 
-		ret = reset_control_deassert(rst);
+		/* just check presence of the reset control in DT */
 		reset_control_put(rst);
-		if (ret)
-			return ret;
 	}
 
 	ahub = devm_kzalloc(&pdev->dev, sizeof(struct tegra30_ahub),
@@ -557,6 +579,12 @@ static int tegra30_ahub_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	ahub->reset = devm_reset_control_array_get_exclusive(&pdev->dev);
+	if (IS_ERR(ahub->reset)) {
+		dev_err(&pdev->dev, "Can't get resets: %pe\n", ahub->reset);
+		return PTR_ERR(ahub->reset);
+	}
+
 	res0 = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	regs_apbif = devm_ioremap_resource(&pdev->dev, res0);
 	if (IS_ERR(regs_apbif))

sound/soc/tegra/tegra30_ahub.h

@@ -511,6 +511,7 @@ struct tegra30_ahub_soc_data {
 struct tegra30_ahub {
 	const struct tegra30_ahub_soc_data *soc_data;
 	struct device *dev;
+	struct reset_control *reset;
 	struct clk_bulk_data clocks[2];
 	unsigned int nclocks;
 	resource_size_t apbif_addr;