linux-kernel - [PATCH v5 7/9] drm/tegra: falcon: Set DMACTX field on DMA transactions

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Date:   Mon, 16 May 2022 11:52:56 +0300
From:   cyndis@...si.fi
To:     thierry.reding@...il.com, jonathanh@...dia.com, joro@...tes.org,
        will@...nel.org, robin.murphy@....com, robh+dt@...nel.org,
        krzysztof.kozlowski@...onical.com
Cc:     linux-tegra@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Mikko Perttunen <mperttunen@...dia.com>
Subject: [PATCH v5 7/9] drm/tegra: falcon: Set DMACTX field on DMA transactions

From: Mikko Perttunen <mperttunen@...dia.com>

The DMACTX field determines which context, as specified in the
TRANSCFG register, is used. While during boot it doesn't matter
which is used, later on it matters and this value is reused by
the firmware.

Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
---
 drivers/gpu/drm/tegra/falcon.c | 8 ++++++++
 drivers/gpu/drm/tegra/falcon.h | 1 +
 2 files changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/tegra/falcon.c b/drivers/gpu/drm/tegra/falcon.c
index 3762d87759d9..c0d85463eb1a 100644
--- a/drivers/gpu/drm/tegra/falcon.c
+++ b/drivers/gpu/drm/tegra/falcon.c
@@ -48,6 +48,14 @@ static int falcon_copy_chunk(struct falcon *falcon,
 	if (target == FALCON_MEMORY_IMEM)
 		cmd |= FALCON_DMATRFCMD_IMEM;
 
+	/*
+	 * Use second DMA context (i.e. the one for firmware). Strictly
+	 * speaking, at this point both DMA contexts point to the firmware
+	 * stream ID, but this register's value will be reused by the firmware
+	 * for later DMA transactions, so we need to use the correct value.
+	 */
+	cmd |= FALCON_DMATRFCMD_DMACTX(1);
+
 	falcon_writel(falcon, offset, FALCON_DMATRFMOFFS);
 	falcon_writel(falcon, base, FALCON_DMATRFFBOFFS);
 	falcon_writel(falcon, cmd, FALCON_DMATRFCMD);
diff --git a/drivers/gpu/drm/tegra/falcon.h b/drivers/gpu/drm/tegra/falcon.h
index c56ee32d92ee..1955cf11a8a6 100644
--- a/drivers/gpu/drm/tegra/falcon.h
+++ b/drivers/gpu/drm/tegra/falcon.h
@@ -50,6 +50,7 @@
 #define FALCON_DMATRFCMD_IDLE			(1 << 1)
 #define FALCON_DMATRFCMD_IMEM			(1 << 4)
 #define FALCON_DMATRFCMD_SIZE_256B		(6 << 8)
+#define FALCON_DMATRFCMD_DMACTX(v)		(((v) & 0x7) << 12)
 
 #define FALCON_DMATRFFBOFFS			0x0000111c
 
-- 
2.36.1