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From:   Olivier Moysan <olivier.moysan@st.com>
To:     <lgirdwood@gmail.com>, <broonie@kernel.org>, <perex@perex.cz>,
        <tiwai@suse.com>, <mcoquelin.stm32@gmail.com>,
        <alexandre.torgue@st.com>, <alsa-devel@alsa-project.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        <linux-kernel@vger.kernel.org>, <olivier.moysan@st.com>
Subject: [PATCH] ASoC: stm32: sai: fix possible circular locking
Date:   Thu, 9 Jan 2020 09:32:54 +0100
Message-ID: <20200109083254.478-1-olivier.moysan@st.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In current driver, locks can be taken as follows:
- Register access: take a lock on regmap config and then on clock.
- Master clock provider: take a lock on clock and then on regmap config.
This can lead to the circular locking summarized below.

Remove peripheral clock management through regmap framework, and manage
peripheral clock in driver instead. On register access, lock on clock
is taken first, which allows to avoid possible locking issue.

[ 6696.561513] ======================================================
[ 6696.567670] WARNING: possible circular locking dependency detected
[ 6696.573842] 4.19.49 #866 Not tainted
[ 6696.577397] ------------------------------------------------------
[ 6696.583566] pulseaudio/6439 is trying to acquire lock:
[ 6696.588697] 87b0a25b (enable_lock){..-.}, at: clk_enable_lock+0x64/0x128
[ 6696.595377]
[ 6696.595377] but task is already holding lock:
[ 6696.601197] d858f825 (stm32_sai_sub:1342:(sai->regmap_config)->lock){....}
...
[ 6696.812513]  Possible unsafe locking scenario:
[ 6696.812513]
[ 6696.818418]        CPU0                    CPU1
[ 6696.822935]        ----                    ----
[ 6696.827451]   lock(stm32_sai_sub:1342:(sai->regmap_config)->lock);
[ 6696.833618]                                lock(enable_lock);
[ 6696.839350]                                lock(stm32_sai_sub:1342:
                                              (sai->regmap_config)->lock);
[ 6696.848035]   lock(enable_lock);

Fixes: 03e78a242a15 ("ASoC: stm32: sai: add h7 support")

Signed-off-by: Olivier Moysan <olivier.moysan@st.com>
---
 sound/soc/stm/stm32_sai_sub.c | 194 ++++++++++++++++++++++++----------
 1 file changed, 140 insertions(+), 54 deletions(-)

diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c
index 48e629ac2d88..30bcd5d3a32a 100644
--- a/sound/soc/stm/stm32_sai_sub.c
+++ b/sound/soc/stm/stm32_sai_sub.c
@@ -184,6 +184,56 @@ static bool stm32_sai_sub_writeable_reg(struct device *dev, unsigned int reg)
 	}
 }
 
+static int stm32_sai_sub_reg_up(struct stm32_sai_sub_data *sai,
+				unsigned int reg, unsigned int mask,
+				unsigned int val)
+{
+	int ret;
+
+	ret = clk_enable(sai->pdata->pclk);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_update_bits(sai->regmap, reg, mask, val);
+
+	clk_disable(sai->pdata->pclk);
+
+	return ret;
+}
+
+static int stm32_sai_sub_reg_wr(struct stm32_sai_sub_data *sai,
+				unsigned int reg, unsigned int mask,
+				unsigned int val)
+{
+	int ret;
+
+	ret = clk_enable(sai->pdata->pclk);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_write_bits(sai->regmap, reg, mask, val);
+
+	clk_disable(sai->pdata->pclk);
+
+	return ret;
+}
+
+static int stm32_sai_sub_reg_rd(struct stm32_sai_sub_data *sai,
+				unsigned int reg, unsigned int *val)
+{
+	int ret;
+
+	ret = clk_enable(sai->pdata->pclk);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_read(sai->regmap, reg, val);
+
+	clk_disable(sai->pdata->pclk);
+
+	return ret;
+}
+
 static const struct regmap_config stm32_sai_sub_regmap_config_f4 = {
 	.reg_bits = 32,
 	.reg_stride = 4,
@@ -295,7 +345,7 @@ static int stm32_sai_set_clk_div(struct stm32_sai_sub_data *sai,
 
 	mask = SAI_XCR1_MCKDIV_MASK(SAI_XCR1_MCKDIV_WIDTH(version));
 	cr1 = SAI_XCR1_MCKDIV_SET(div);
-	ret = regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX, mask, cr1);
+	ret = stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX, mask, cr1);
 	if (ret < 0)
 		dev_err(&sai->pdev->dev, "Failed to update CR1 register\n");
 
@@ -372,8 +422,8 @@ static int stm32_sai_mclk_enable(struct clk_hw *hw)
 
 	dev_dbg(&sai->pdev->dev, "Enable master clock\n");
 
-	return regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX,
-				  SAI_XCR1_MCKEN, SAI_XCR1_MCKEN);
+	return stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX,
+				    SAI_XCR1_MCKEN, SAI_XCR1_MCKEN);
 }
 
 static void stm32_sai_mclk_disable(struct clk_hw *hw)
@@ -383,7 +433,7 @@ static void stm32_sai_mclk_disable(struct clk_hw *hw)
 
 	dev_dbg(&sai->pdev->dev, "Disable master clock\n");
 
-	regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX, SAI_XCR1_MCKEN, 0);
+	stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX, SAI_XCR1_MCKEN, 0);
 }
 
 static const struct clk_ops mclk_ops = {
@@ -446,15 +496,15 @@ static irqreturn_t stm32_sai_isr(int irq, void *devid)
 	unsigned int sr, imr, flags;
 	snd_pcm_state_t status = SNDRV_PCM_STATE_RUNNING;
 
-	regmap_read(sai->regmap, STM_SAI_IMR_REGX, &imr);
-	regmap_read(sai->regmap, STM_SAI_SR_REGX, &sr);
+	stm32_sai_sub_reg_rd(sai, STM_SAI_IMR_REGX, &imr);
+	stm32_sai_sub_reg_rd(sai, STM_SAI_SR_REGX, &sr);
 
 	flags = sr & imr;
 	if (!flags)
 		return IRQ_NONE;
 
-	regmap_write_bits(sai->regmap, STM_SAI_CLRFR_REGX, SAI_XCLRFR_MASK,
-			  SAI_XCLRFR_MASK);
+	stm32_sai_sub_reg_wr(sai, STM_SAI_CLRFR_REGX, SAI_XCLRFR_MASK,
+			     SAI_XCLRFR_MASK);
 
 	if (!sai->substream) {
 		dev_err(&pdev->dev, "Device stopped. Spurious IRQ 0x%x\n", sr);
@@ -503,8 +553,8 @@ static int stm32_sai_set_sysclk(struct snd_soc_dai *cpu_dai,
 	int ret;
 
 	if (dir == SND_SOC_CLOCK_OUT && sai->sai_mclk) {
-		ret = regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX,
-					 SAI_XCR1_NODIV,
+		ret = stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX,
+					   SAI_XCR1_NODIV,
 					 freq ? 0 : SAI_XCR1_NODIV);
 		if (ret < 0)
 			return ret;
@@ -583,7 +633,7 @@ static int stm32_sai_set_dai_tdm_slot(struct snd_soc_dai *cpu_dai, u32 tx_mask,
 
 	slotr_mask |= SAI_XSLOTR_SLOTEN_MASK;
 
-	regmap_update_bits(sai->regmap, STM_SAI_SLOTR_REGX, slotr_mask, slotr);
+	stm32_sai_sub_reg_up(sai, STM_SAI_SLOTR_REGX, slotr_mask, slotr);
 
 	sai->slot_width = slot_width;
 	sai->slots = slots;
@@ -665,7 +715,7 @@ static int stm32_sai_set_dai_fmt(struct snd_soc_dai *cpu_dai, unsigned int fmt)
 	cr1_mask |= SAI_XCR1_CKSTR;
 	frcr_mask |= SAI_XFRCR_FSPOL;
 
-	regmap_update_bits(sai->regmap, STM_SAI_FRCR_REGX, frcr_mask, frcr);
+	stm32_sai_sub_reg_up(sai, STM_SAI_FRCR_REGX, frcr_mask, frcr);
 
 	/* DAI clock master masks */
 	switch (fmt & SND_SOC_DAIFMT_MASTER_MASK) {
@@ -693,7 +743,7 @@ static int stm32_sai_set_dai_fmt(struct snd_soc_dai *cpu_dai, unsigned int fmt)
 	cr1_mask |= SAI_XCR1_SLAVE;
 
 conf_update:
-	ret = regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX, cr1_mask, cr1);
+	ret = stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX, cr1_mask, cr1);
 	if (ret < 0) {
 		dev_err(cpu_dai->dev, "Failed to update CR1 register\n");
 		return ret;
@@ -730,12 +780,12 @@ static int stm32_sai_startup(struct snd_pcm_substream *substream,
 	}
 
 	/* Enable ITs */
-	regmap_write_bits(sai->regmap, STM_SAI_CLRFR_REGX,
-			  SAI_XCLRFR_MASK, SAI_XCLRFR_MASK);
+	stm32_sai_sub_reg_wr(sai, STM_SAI_CLRFR_REGX,
+			     SAI_XCLRFR_MASK, SAI_XCLRFR_MASK);
 
 	imr = SAI_XIMR_OVRUDRIE;
 	if (STM_SAI_IS_CAPTURE(sai)) {
-		regmap_read(sai->regmap, STM_SAI_CR2_REGX, &cr2);
+		stm32_sai_sub_reg_rd(sai, STM_SAI_CR2_REGX, &cr2);
 		if (cr2 & SAI_XCR2_MUTECNT_MASK)
 			imr |= SAI_XIMR_MUTEDETIE;
 	}
@@ -745,8 +795,8 @@ static int stm32_sai_startup(struct snd_pcm_substream *substream,
 	else
 		imr |= SAI_XIMR_AFSDETIE | SAI_XIMR_LFSDETIE;
 
-	regmap_update_bits(sai->regmap, STM_SAI_IMR_REGX,
-			   SAI_XIMR_MASK, imr);
+	stm32_sai_sub_reg_up(sai, STM_SAI_IMR_REGX,
+			     SAI_XIMR_MASK, imr);
 
 	return 0;
 }
@@ -763,10 +813,10 @@ static int stm32_sai_set_config(struct snd_soc_dai *cpu_dai,
 	 * SAI fifo threshold is set to half fifo, to keep enough space
 	 * for DMA incoming bursts.
 	 */
-	regmap_write_bits(sai->regmap, STM_SAI_CR2_REGX,
-			  SAI_XCR2_FFLUSH | SAI_XCR2_FTH_MASK,
-			  SAI_XCR2_FFLUSH |
-			  SAI_XCR2_FTH_SET(STM_SAI_FIFO_TH_HALF));
+	stm32_sai_sub_reg_wr(sai, STM_SAI_CR2_REGX,
+			     SAI_XCR2_FFLUSH | SAI_XCR2_FTH_MASK,
+			     SAI_XCR2_FFLUSH |
+			     SAI_XCR2_FTH_SET(STM_SAI_FIFO_TH_HALF));
 
 	/* DS bits in CR1 not set for SPDIF (size forced to 24 bits).*/
 	if (STM_SAI_PROTOCOL_IS_SPDIF(sai)) {
@@ -795,7 +845,7 @@ static int stm32_sai_set_config(struct snd_soc_dai *cpu_dai,
 	if ((sai->slots == 2) && (params_channels(params) == 1))
 		cr1 |= SAI_XCR1_MONO;
 
-	ret = regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX, cr1_mask, cr1);
+	ret = stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX, cr1_mask, cr1);
 	if (ret < 0) {
 		dev_err(cpu_dai->dev, "Failed to update CR1 register\n");
 		return ret;
@@ -809,7 +859,7 @@ static int stm32_sai_set_slots(struct snd_soc_dai *cpu_dai)
 	struct stm32_sai_sub_data *sai = snd_soc_dai_get_drvdata(cpu_dai);
 	int slotr, slot_sz;
 
-	regmap_read(sai->regmap, STM_SAI_SLOTR_REGX, &slotr);
+	stm32_sai_sub_reg_rd(sai, STM_SAI_SLOTR_REGX, &slotr);
 
 	/*
 	 * If SLOTSZ is set to auto in SLOTR, align slot width on data size
@@ -831,16 +881,16 @@ static int stm32_sai_set_slots(struct snd_soc_dai *cpu_dai)
 		sai->slots = 2;
 
 	/* The number of slots in the audio frame is equal to NBSLOT[3:0] + 1*/
-	regmap_update_bits(sai->regmap, STM_SAI_SLOTR_REGX,
-			   SAI_XSLOTR_NBSLOT_MASK,
-			   SAI_XSLOTR_NBSLOT_SET((sai->slots - 1)));
+	stm32_sai_sub_reg_up(sai, STM_SAI_SLOTR_REGX,
+			     SAI_XSLOTR_NBSLOT_MASK,
+			     SAI_XSLOTR_NBSLOT_SET((sai->slots - 1)));
 
 	/* Set default slots mask if not already set from DT */
 	if (!(slotr & SAI_XSLOTR_SLOTEN_MASK)) {
 		sai->slot_mask = (1 << sai->slots) - 1;
-		regmap_update_bits(sai->regmap,
-				   STM_SAI_SLOTR_REGX, SAI_XSLOTR_SLOTEN_MASK,
-				   SAI_XSLOTR_SLOTEN_SET(sai->slot_mask));
+		stm32_sai_sub_reg_up(sai,
+				     STM_SAI_SLOTR_REGX, SAI_XSLOTR_SLOTEN_MASK,
+				     SAI_XSLOTR_SLOTEN_SET(sai->slot_mask));
 	}
 
 	dev_dbg(cpu_dai->dev, "Slots %d, slot width %d\n",
@@ -870,14 +920,14 @@ static void stm32_sai_set_frame(struct snd_soc_dai *cpu_dai)
 	dev_dbg(cpu_dai->dev, "Frame length %d, frame active %d\n",
 		sai->fs_length, fs_active);
 
-	regmap_update_bits(sai->regmap, STM_SAI_FRCR_REGX, frcr_mask, frcr);
+	stm32_sai_sub_reg_up(sai, STM_SAI_FRCR_REGX, frcr_mask, frcr);
 
 	if ((sai->fmt & SND_SOC_DAIFMT_FORMAT_MASK) == SND_SOC_DAIFMT_LSB) {
 		offset = sai->slot_width - sai->data_size;
 
-		regmap_update_bits(sai->regmap, STM_SAI_SLOTR_REGX,
-				   SAI_XSLOTR_FBOFF_MASK,
-				   SAI_XSLOTR_FBOFF_SET(offset));
+		stm32_sai_sub_reg_up(sai, STM_SAI_SLOTR_REGX,
+				     SAI_XSLOTR_FBOFF_MASK,
+				     SAI_XSLOTR_FBOFF_SET(offset));
 	}
 }
 
@@ -994,9 +1044,9 @@ static int stm32_sai_configure_clock(struct snd_soc_dai *cpu_dai,
 					return -EINVAL;
 				}
 
-				regmap_update_bits(sai->regmap,
-						   STM_SAI_CR1_REGX,
-						   SAI_XCR1_OSR, cr1);
+				stm32_sai_sub_reg_up(sai,
+						     STM_SAI_CR1_REGX,
+						     SAI_XCR1_OSR, cr1);
 
 				div = stm32_sai_get_clk_div(sai, sai_clk_rate,
 							    sai->mclk_rate);
@@ -1058,12 +1108,12 @@ static int stm32_sai_trigger(struct snd_pcm_substream *substream, int cmd,
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
 		dev_dbg(cpu_dai->dev, "Enable DMA and SAI\n");
 
-		regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX,
-				   SAI_XCR1_DMAEN, SAI_XCR1_DMAEN);
+		stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX,
+				     SAI_XCR1_DMAEN, SAI_XCR1_DMAEN);
 
 		/* Enable SAI */
-		ret = regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX,
-					 SAI_XCR1_SAIEN, SAI_XCR1_SAIEN);
+		ret = stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX,
+					   SAI_XCR1_SAIEN, SAI_XCR1_SAIEN);
 		if (ret < 0)
 			dev_err(cpu_dai->dev, "Failed to update CR1 register\n");
 		break;
@@ -1072,16 +1122,16 @@ static int stm32_sai_trigger(struct snd_pcm_substream *substream, int cmd,
 	case SNDRV_PCM_TRIGGER_STOP:
 		dev_dbg(cpu_dai->dev, "Disable DMA and SAI\n");
 
-		regmap_update_bits(sai->regmap, STM_SAI_IMR_REGX,
-				   SAI_XIMR_MASK, 0);
+		stm32_sai_sub_reg_up(sai, STM_SAI_IMR_REGX,
+				     SAI_XIMR_MASK, 0);
 
-		regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX,
-				   SAI_XCR1_SAIEN,
-				   (unsigned int)~SAI_XCR1_SAIEN);
+		stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX,
+				     SAI_XCR1_SAIEN,
+				     (unsigned int)~SAI_XCR1_SAIEN);
 
-		ret = regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX,
-					 SAI_XCR1_DMAEN,
-					 (unsigned int)~SAI_XCR1_DMAEN);
+		ret = stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX,
+					   SAI_XCR1_DMAEN,
+					   (unsigned int)~SAI_XCR1_DMAEN);
 		if (ret < 0)
 			dev_err(cpu_dai->dev, "Failed to update CR1 register\n");
 
@@ -1101,7 +1151,7 @@ static void stm32_sai_shutdown(struct snd_pcm_substream *substream,
 	struct stm32_sai_sub_data *sai = snd_soc_dai_get_drvdata(cpu_dai);
 	unsigned long flags;
 
-	regmap_update_bits(sai->regmap, STM_SAI_IMR_REGX, SAI_XIMR_MASK, 0);
+	stm32_sai_sub_reg_up(sai, STM_SAI_IMR_REGX, SAI_XIMR_MASK, 0);
 
 	clk_disable_unprepare(sai->sai_ck);
 
@@ -1169,7 +1219,7 @@ static int stm32_sai_dai_probe(struct snd_soc_dai *cpu_dai)
 	cr1_mask |= SAI_XCR1_SYNCEN_MASK;
 	cr1 |= SAI_XCR1_SYNCEN_SET(sai->sync);
 
-	return regmap_update_bits(sai->regmap, STM_SAI_CR1_REGX, cr1_mask, cr1);
+	return stm32_sai_sub_reg_up(sai, STM_SAI_CR1_REGX, cr1_mask, cr1);
 }
 
 static const struct snd_soc_dai_ops stm32_sai_pcm_dai_ops = {
@@ -1322,8 +1372,13 @@ static int stm32_sai_sub_parse_of(struct platform_device *pdev,
 	if (STM_SAI_HAS_PDM(sai) && STM_SAI_IS_SUB_A(sai))
 		sai->regmap_config = &stm32_sai_sub_regmap_config_h7;
 
-	sai->regmap = devm_regmap_init_mmio_clk(&pdev->dev, "sai_ck",
-						base, sai->regmap_config);
+	/*
+	 * Do not manage peripheral clock through regmap framework as this
+	 * can lead to circular locking issue with sai master clock provider.
+	 * Manage peripheral clock directly in driver instead.
+	 */
+	sai->regmap = devm_regmap_init_mmio(&pdev->dev, base,
+					    sai->regmap_config);
 	if (IS_ERR(sai->regmap)) {
 		dev_err(&pdev->dev, "Failed to initialize MMIO\n");
 		return PTR_ERR(sai->regmap);
@@ -1420,6 +1475,10 @@ static int stm32_sai_sub_parse_of(struct platform_device *pdev,
 		return PTR_ERR(sai->sai_ck);
 	}
 
+	ret = clk_prepare(sai->pdata->pclk);
+	if (ret < 0)
+		return ret;
+
 	if (STM_SAI_IS_F4(sai->pdata))
 		return 0;
 
@@ -1501,22 +1560,48 @@ static int stm32_sai_sub_probe(struct platform_device *pdev)
 	return 0;
 }
 
+static int stm32_sai_sub_remove(struct platform_device *pdev)
+{
+	struct stm32_sai_sub_data *sai = dev_get_drvdata(&pdev->dev);
+
+	clk_unprepare(sai->pdata->pclk);
+
+	return 0;
+}
+
 #ifdef CONFIG_PM_SLEEP
 static int stm32_sai_sub_suspend(struct device *dev)
 {
 	struct stm32_sai_sub_data *sai = dev_get_drvdata(dev);
+	int ret;
+
+	ret = clk_enable(sai->pdata->pclk);
+	if (ret < 0)
+		return ret;
 
 	regcache_cache_only(sai->regmap, true);
 	regcache_mark_dirty(sai->regmap);
+
+	clk_disable(sai->pdata->pclk);
+
 	return 0;
 }
 
 static int stm32_sai_sub_resume(struct device *dev)
 {
 	struct stm32_sai_sub_data *sai = dev_get_drvdata(dev);
+	int ret;
+
+	ret = clk_enable(sai->pdata->pclk);
+	if (ret < 0)
+		return ret;
 
 	regcache_cache_only(sai->regmap, false);
-	return regcache_sync(sai->regmap);
+	ret = regcache_sync(sai->regmap);
+
+	clk_disable(sai->pdata->pclk);
+
+	return ret;
 }
 #endif /* CONFIG_PM_SLEEP */
 
@@ -1531,6 +1616,7 @@ static struct platform_driver stm32_sai_sub_driver = {
 		.pm = &stm32_sai_sub_pm_ops,
 	},
 	.probe = stm32_sai_sub_probe,
+	.remove = stm32_sai_sub_remove,
 };
 
 module_platform_driver(stm32_sai_sub_driver);
-- 
2.17.1