linux-kernel - [PATCH v8 01/11] dmaengine: Add DMA_PREP_LOCK/DMA_PREP

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Message-Id: <20251106-qcom-qce-cmd-descr-v8-1-ecddca23ca26@linaro.org>
Date: Thu, 06 Nov 2025 12:33:57 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Vinod Koul <vkoul@...nel.org>, Jonathan Corbet <corbet@....net>, 
 Thara Gopinath <thara.gopinath@...il.com>, 
 Herbert Xu <herbert@...dor.apana.org.au>, 
 "David S. Miller" <davem@...emloft.net>, 
 Udit Tiwari <quic_utiwari@...cinc.com>, 
 Daniel Perez-Zoghbi <dperezzo@...cinc.com>, 
 Md Sadre Alam <mdalam@....qualcomm.com>
Cc: dmaengine@...r.kernel.org, linux-doc@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
 linux-crypto@...r.kernel.org, 
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH v8 01/11] dmaengine: Add DMA_PREP_LOCK/DMA_PREP_UNLOCK
 flags

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

Some DMA engines may be accessed from linux and the TrustZone
simultaneously. In order to allow synchronization, add lock and unlock
flags for the command descriptor that allow the caller to request the
controller to be locked for the duration of the transaction in an
implementation-dependent way.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
 Documentation/driver-api/dmaengine/provider.rst | 9 +++++++++
 include/linux/dmaengine.h                       | 6 ++++++
 2 files changed, 15 insertions(+)

diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst
index 1594598b331782e4dddcf992159c724111db9cf3..6428211405472dd1147e363f5786acc91d95ed43 100644
--- a/Documentation/driver-api/dmaengine/provider.rst
+++ b/Documentation/driver-api/dmaengine/provider.rst
@@ -630,6 +630,15 @@ DMA_CTRL_REUSE
   - This flag is only supported if the channel reports the DMA_LOAD_EOT
     capability.

+- DMA_PREP_LOCK
+
+  - If set, the DMA controller will be locked for the duration of the current
+    transaction.
+
+- DMA_PREP_UNLOCK
+
+  - If set, DMA will release he controller lock.
+
 General Design Notes
 ====================

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 99efe2b9b4ea9844ca6161208362ef18ef111d96..c02be4bc8ac4c3db47c7c11751b949e3479e7cb8 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -200,6 +200,10 @@ struct dma_vec {
  *  transaction is marked with DMA_PREP_REPEAT will cause the new transaction
  *  to never be processed and stay in the issued queue forever. The flag is
  *  ignored if the previous transaction is not a repeated transaction.
+ *  @DMA_PREP_LOCK: tell the driver that there is a lock bit set on command
+ *  descriptor.
+ *  @DMA_PREP_UNLOCK: tell the driver that there is a un-lock bit set on command
+ *  descriptor.
  */
 enum dma_ctrl_flags {
 	DMA_PREP_INTERRUPT = (1 << 0),
@@ -212,6 +216,8 @@ enum dma_ctrl_flags {
 	DMA_PREP_CMD = (1 << 7),
 	DMA_PREP_REPEAT = (1 << 8),
 	DMA_PREP_LOAD_EOT = (1 << 9),
+	DMA_PREP_LOCK = (1 << 10),
+	DMA_PREP_UNLOCK = (1 << 11),
 };

 /**

-- 
2.51.0