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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Dmitry Osipenko <digetx@gmail.com>,
        Jon Hunter <jonathanh@nvidia.com>,
        Vinod Koul <vkoul@kernel.org>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.2 011/131] dmaengine: tegra-apb: Error out if DMA_PREP_INTERRUPT flag is unset
Date:   Mon,  5 Aug 2019 15:01:38 +0200
Message-Id: <20190805124952.183362810@linuxfoundation.org>
In-Reply-To: <20190805124951.453337465@linuxfoundation.org>
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[ Upstream commit dc161064beb83c668e0f85766b92b1e7ed186e58 ]

Apparently driver was never tested with DMA_PREP_INTERRUPT flag being
unset since it completely disables interrupt handling instead of skipping
the callbacks invocations, hence putting channel into unusable state.

The flag is always set by all of kernel drivers that use APB DMA, so let's
error out in otherwise case for consistency. It won't be difficult to
support that case properly if ever will be needed.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/dma/tegra20-apb-dma.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index ef317c90fbe1e..79e9593815f12 100644
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -977,8 +977,12 @@ static struct dma_async_tx_descriptor *tegra_dma_prep_slave_sg(
 		csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
 	}
 
-	if (flags & DMA_PREP_INTERRUPT)
+	if (flags & DMA_PREP_INTERRUPT) {
 		csr |= TEGRA_APBDMA_CSR_IE_EOC;
+	} else {
+		WARN_ON_ONCE(1);
+		return NULL;
+	}
 
 	apb_seq |= TEGRA_APBDMA_APBSEQ_WRAP_WORD_1;
 
@@ -1120,8 +1124,12 @@ static struct dma_async_tx_descriptor *tegra_dma_prep_dma_cyclic(
 		csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
 	}
 
-	if (flags & DMA_PREP_INTERRUPT)
+	if (flags & DMA_PREP_INTERRUPT) {
 		csr |= TEGRA_APBDMA_CSR_IE_EOC;
+	} else {
+		WARN_ON_ONCE(1);
+		return NULL;
+	}
 
 	apb_seq |= TEGRA_APBDMA_APBSEQ_WRAP_WORD_1;
 
-- 
2.20.1