linux-kernel - [PATCH v2 1/7] dt-bindings: stm32-dma: Add DMA/MDMA chaining support bindings

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Date:   Fri, 28 Sep 2018 10:36:28 +0200
From:   Pierre-Yves MORDRET <pierre-yves.mordret@...com>
To:     Vinod Koul <vkoul@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Dan Williams <dan.j.williams@...el.com>,
        <devicetree@...r.kernel.org>, <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     Pierre-Yves MORDRET <pierre-yves.mordret@...com>
Subject: [PATCH v2 1/7] dt-bindings: stm32-dma: Add DMA/MDMA chaining support bindings

From: M'boumba Cedric Madianga <cedric.madianga@...il.com>

This patch adds dma bindings to support DMA/MDMA chaining transfer.
1 bit is to manage both DMA FIFO Threshold
1 bit is to manage DMA/MDMA Chaining features.
2 bits are used to specify SDRAM size to use for DMA/MDMA chaining.
The size in bytes of a certain order is given by the formula:
    (2 ^ order) * PAGE_SIZE.
The order is given by those 2 bits.
For cyclic, whether chaining is chosen, any value above 1 can be set :
SRAM buffer size will rely on period size and not on this DT value.

Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@...com>
---
  Version history:
    v1:
       * Initial
---
---
 .../devicetree/bindings/dma/stm32-dma.txt          | 27 +++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/dma/stm32-dma.txt b/Documentation/devicetree/bindings/dma/stm32-dma.txt
index c5f5190..2bac8c7 100644
--- a/Documentation/devicetree/bindings/dma/stm32-dma.txt
+++ b/Documentation/devicetree/bindings/dma/stm32-dma.txt
@@ -17,6 +17,12 @@ Optional properties:
 - resets: Reference to a reset controller asserting the DMA controller
 - st,mem2mem: boolean; if defined, it indicates that the controller supports
   memory-to-memory transfer
+- dmas: A list of eight dma specifiers, one for each entry in dma-names.
+  Refer to stm32-mdma.txt for more details.
+- dma-names: should contain "ch0", "ch1", "ch2", "ch3", "ch4", "ch5", "ch6" and
+  "ch7" and represents each STM32 DMA channel connected to a STM32 MDMA one.
+- memory-region : phandle to a node describing memory to be used for
+  M2M intermediate transfer between DMA and MDMA.
 
 Example:
 
@@ -36,6 +42,16 @@ Example:
 		st,mem2mem;
 		resets = <&rcc 150>;
 		dma-requests = <8>;
+		dmas = <&mdma1 8 0x10 0x1200000a 0x40026408 0x00000020 1>,
+		       <&mdma1 9 0x10 0x1200000a 0x40026408 0x00000800 1>,
+		       <&mdma1 10 0x10 0x1200000a 0x40026408 0x00200000 1>,
+		       <&mdma1 11 0x10 0x1200000a 0x40026408 0x08000000 1>,
+		       <&mdma1 12 0x10 0x1200000a 0x4002640C 0x00000020 1>,
+		       <&mdma1 13 0x10 0x1200000a 0x4002640C 0x00000800 1>,
+		       <&mdma1 14 0x10 0x1200000a 0x4002640C 0x00200000 1>,
+		       <&mdma1 15 0x10 0x1200000a 0x4002640C 0x08000000 1>;
+		dma-names = "ch0", "ch1", "ch2", "ch3", "ch4", "ch5", "ch6", "ch7";
+		memory-region = <&sram_dmapool>;
 	};
 
 * DMA client
@@ -68,7 +84,16 @@ channel: a phandle to the DMA controller plus the following four integer cells:
 	0x1: 1/2 full FIFO
 	0x2: 3/4 full FIFO
 	0x3: full FIFO
-
+ -bit 2: Intermediate M2M transfer from/to DDR to/from SRAM throughout MDMA
+	0: MDMA not used to generate an intermediate M2M transfer
+	1: MDMA used to generate an intermediate M2M transfer.
+ -bit 3-4: indicated SRAM Buffer size in (2^order)*PAGE_SIZE.
+	PAGE_SIZE is given by Linux at 4KiB: include/asm-generic/page.h.
+	Order is given by those 2 bits starting at 0.
+	Valid only whether Intermediate M2M transfer is set.
+	For cyclic, whether Intermediate M2M transfer is chosen, any value can
+	be set: SRAM buffer size will rely on period size and not on this DT
+	value.
 
 Example:
 
-- 
2.7.4