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From:   Akhil R <akhilrajeev@nvidia.com>
To:     <robh+dt@kernel.org>, <devicetree@vger.kernel.org>,
        <christian.koenig@amd.com>, <digetx@gmail.com>,
        <jonathanh@nvidia.com>, <ldewangan@nvidia.com>,
        <linux-i2c@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-tegra@vger.kernel.org>, <sumit.semwal@linaro.org>,
        <thierry.reding@gmail.com>, <wsa@kernel.org>
CC:     <akhilrajeev@nvidia.com>
Subject: [PATCH 1/2] i2c: tegra: Add GPCDMA support
Date:   Wed, 20 Jul 2022 18:11:47 +0530
Message-ID: <20220720124148.7969-2-akhilrajeev@nvidia.com>
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Update the DMA initialization and checks to support GPCDMA.
Also add a mechanism to fall back to PIO mode, if DMA is
not available or if initialization returns error.

Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
---
 drivers/i2c/busses/i2c-tegra.c | 39 ++++++++++++++++------------------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 2941e42aa6a0..26a3d5805a9e 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -188,7 +188,6 @@ enum msg_end_type {
  *		allowing 0 length transfers.
  * @supports_bus_clear: Bus Clear support to recover from bus hang during
  *		SDA stuck low from device for some unknown reasons.
- * @has_apb_dma: Support of APBDMA on corresponding Tegra chip.
  * @tlow_std_mode: Low period of the clock in standard mode.
  * @thigh_std_mode: High period of the clock in standard mode.
  * @tlow_fast_fastplus_mode: Low period of the clock in fast/fast-plus modes.
@@ -215,7 +214,6 @@ struct tegra_i2c_hw_feature {
 	bool has_mst_fifo;
 	const struct i2c_adapter_quirks *quirks;
 	bool supports_bus_clear;
-	bool has_apb_dma;
 	u32 tlow_std_mode;
 	u32 thigh_std_mode;
 	u32 tlow_fast_fastplus_mode;
@@ -253,6 +251,7 @@ struct tegra_i2c_hw_feature {
  * @dma_phys: handle to DMA resources
  * @dma_buf: pointer to allocated DMA buffer
  * @dma_buf_size: DMA buffer size
+ * @dma_support: indicates if DMA can be enabled
  * @dma_mode: indicates active DMA transfer
  * @dma_complete: DMA completion notifier
  * @atomic_mode: indicates active atomic transfer
@@ -289,6 +288,7 @@ struct tegra_i2c_dev {
 
 	bool multimaster_mode;
 	bool atomic_mode;
+	bool dma_support;
 	bool dma_mode;
 	bool msg_read;
 	bool is_dvc;
@@ -443,13 +443,8 @@ static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
 	u32 *dma_buf;
 	int err;
 
-	if (!i2c_dev->hw->has_apb_dma || i2c_dev->is_vi)
-		return 0;
-
-	if (!IS_ENABLED(CONFIG_TEGRA20_APB_DMA)) {
-		dev_dbg(i2c_dev->dev, "DMA support not enabled\n");
-		return 0;
-	}
+	if (!i2c_dev->dma_support)
+		return -EOPNOTSUPP;
 
 	chan = dma_request_chan(i2c_dev->dev, "rx");
 	if (IS_ERR(chan)) {
@@ -486,6 +481,7 @@ static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
 err_out:
 	tegra_i2c_release_dma(i2c_dev);
 	if (err != -EPROBE_DEFER) {
+		i2c_dev->dma_support = false;
 		dev_err(i2c_dev->dev, "cannot use DMA: %d\n", err);
 		dev_err(i2c_dev->dev, "falling back to PIO\n");
 		return 0;
@@ -1251,7 +1247,16 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
 	xfer_size = ALIGN(xfer_size, BYTES_PER_FIFO_WORD);
 
 	i2c_dev->dma_mode = xfer_size > I2C_PIO_MODE_PREFERRED_LEN &&
-			    i2c_dev->dma_buf && !i2c_dev->atomic_mode;
+			   i2c_dev->dma_support && !i2c_dev->atomic_mode;
+
+	/* If DMA is not initialized, initialize it now.
+	 * Fall back to PIO mode, if it fails.
+	 */
+	if (i2c_dev->dma_mode && !i2c_dev->dma_buf) {
+		err = tegra_i2c_init_dma(i2c_dev);
+		if (err)
+			i2c_dev->dma_mode = false;
+	}
 
 	tegra_i2c_config_fifo_trig(i2c_dev, xfer_size);
 
@@ -1473,7 +1478,6 @@ static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = false,
-	.has_apb_dma = true,
 	.tlow_std_mode = 0x4,
 	.thigh_std_mode = 0x2,
 	.tlow_fast_fastplus_mode = 0x4,
@@ -1497,7 +1501,6 @@ static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = false,
-	.has_apb_dma = true,
 	.tlow_std_mode = 0x4,
 	.thigh_std_mode = 0x2,
 	.tlow_fast_fastplus_mode = 0x4,
@@ -1521,7 +1524,6 @@ static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = true,
-	.has_apb_dma = true,
 	.tlow_std_mode = 0x4,
 	.thigh_std_mode = 0x2,
 	.tlow_fast_fastplus_mode = 0x4,
@@ -1545,7 +1547,6 @@ static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = true,
-	.has_apb_dma = true,
 	.tlow_std_mode = 0x4,
 	.thigh_std_mode = 0x2,
 	.tlow_fast_fastplus_mode = 0x4,
@@ -1569,7 +1570,6 @@ static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = true,
-	.has_apb_dma = true,
 	.tlow_std_mode = 0x4,
 	.thigh_std_mode = 0x2,
 	.tlow_fast_fastplus_mode = 0x4,
@@ -1593,7 +1593,6 @@ static const struct tegra_i2c_hw_feature tegra186_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = true,
-	.has_apb_dma = false,
 	.tlow_std_mode = 0x4,
 	.thigh_std_mode = 0x3,
 	.tlow_fast_fastplus_mode = 0x4,
@@ -1617,7 +1616,6 @@ static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
 	.has_mst_fifo = true,
 	.quirks = &tegra194_i2c_quirks,
 	.supports_bus_clear = true,
-	.has_apb_dma = false,
 	.tlow_std_mode = 0x8,
 	.thigh_std_mode = 0x7,
 	.tlow_fast_fastplus_mode = 0x2,
@@ -1657,6 +1655,8 @@ static void tegra_i2c_parse_dt(struct tegra_i2c_dev *i2c_dev)
 
 	if (of_device_is_compatible(np, "nvidia,tegra210-i2c-vi"))
 		i2c_dev->is_vi = true;
+	else
+		i2c_dev->dma_support = !!(of_find_property(np, "dmas", NULL));
 }
 
 static int tegra_i2c_init_reset(struct tegra_i2c_dev *i2c_dev)
@@ -1789,9 +1789,7 @@ static int tegra_i2c_probe(struct platform_device *pdev)
 	if (err)
 		return err;
 
-	err = tegra_i2c_init_dma(i2c_dev);
-	if (err)
-		goto release_clocks;
+	tegra_i2c_init_dma(i2c_dev);
 
 	/*
 	 * VI I2C is in VE power domain which is not always ON and not
@@ -1838,7 +1836,6 @@ static int tegra_i2c_probe(struct platform_device *pdev)
 	pm_runtime_disable(i2c_dev->dev);
 
 	tegra_i2c_release_dma(i2c_dev);
-release_clocks:
 	tegra_i2c_release_clocks(i2c_dev);
 
 	return err;
-- 
2.17.1