linux-kernel - [PATCH v4 2/3] dmaengine: tegra: Add terminate() for Tegra234

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Message-ID: <20220720104045.16099-3-akhilrajeev@nvidia.com>
Date:   Wed, 20 Jul 2022 16:10:44 +0530
From:   Akhil R <akhilrajeev@...dia.com>
To:     <dmaengine@...r.kernel.org>, <jonathanh@...dia.com>,
        <ldewangan@...dia.com>, <linux-kernel@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <p.zabel@...gutronix.de>,
        <thierry.reding@...il.com>, <vkoul@...nel.org>,
        <robh+dt@...nel.org>, <devicetree@...r.kernel.org>
CC:     <akhilrajeev@...dia.com>
Subject: [PATCH v4 2/3] dmaengine: tegra: Add terminate() for Tegra234

In certain cases where the DMA client bus gets corrupted or if the
end device ceases to send/receive data, DMA can wait indefinitely
for the data to be received/sent. Attempting to terminate the transfer
will put the DMA in pause flush mode and it remains there.

The channel is irrecoverable once this pause times out in Tegra194 and
earlier chips. Whereas, from Tegra234, it can be recovered by disabling
the channel and reprograming it.

Hence add a new terminate() function that ignores the outcome of
dma_pause() so that terminate_all() can proceed to disable the channel.

Signed-off-by: Akhil R <akhilrajeev@...dia.com>
Reviewed-by: Jon Hunter <jonathanh@...dia.com>
---
 drivers/dma/tegra186-gpc-dma.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/tegra186-gpc-dma.c b/drivers/dma/tegra186-gpc-dma.c
index 05cd451f541d..fa9bda4a2bc6 100644
--- a/drivers/dma/tegra186-gpc-dma.c
+++ b/drivers/dma/tegra186-gpc-dma.c
@@ -157,8 +157,8 @@
  * If any burst is in flight and DMA paused then this is the time to complete
  * on-flight burst and update DMA status register.
  */
-#define TEGRA_GPCDMA_BURST_COMPLETE_TIME	20
-#define TEGRA_GPCDMA_BURST_COMPLETION_TIMEOUT	100
+#define TEGRA_GPCDMA_BURST_COMPLETE_TIME	10
+#define TEGRA_GPCDMA_BURST_COMPLETION_TIMEOUT	5000 /* 5 msec */
 
 /* Channel base address offset from GPCDMA base address */
 #define TEGRA_GPCDMA_CHANNEL_BASE_ADD_OFFSET	0x20000
@@ -432,6 +432,17 @@ static int tegra_dma_device_resume(struct dma_chan *dc)
 	return 0;
 }
 
+static inline int tegra_dma_pause_noerr(struct tegra_dma_channel *tdc)
+{
+	/* Return 0 irrespective of PAUSE status.
+	 * This is useful to recover channels that can exit out of flush
+	 * state when the channel is disabled.
+	 */
+
+	tegra_dma_pause(tdc);
+	return 0;
+}
+
 static void tegra_dma_disable(struct tegra_dma_channel *tdc)
 {
 	u32 csr, status;
@@ -1292,6 +1303,14 @@ static const struct tegra_dma_chip_data tegra194_dma_chip_data = {
 	.terminate = tegra_dma_pause,
 };
 
+static const struct tegra_dma_chip_data tegra234_dma_chip_data = {
+	.nr_channels = 31,
+	.channel_reg_size = SZ_64K,
+	.max_dma_count = SZ_1G,
+	.hw_support_pause = true,
+	.terminate = tegra_dma_pause_noerr,
+};
+
 static const struct of_device_id tegra_dma_of_match[] = {
 	{
 		.compatible = "nvidia,tegra186-gpcdma",
@@ -1299,6 +1318,9 @@ static const struct of_device_id tegra_dma_of_match[] = {
 	}, {
 		.compatible = "nvidia,tegra194-gpcdma",
 		.data = &tegra194_dma_chip_data,
+	}, {
+		.compatible = "nvidia,tegra234-gpcdma",
+		.data = &tegra234_dma_chip_data,
 	}, {
 	},
 };
-- 
2.17.1