linux-kernel - [PATCH] dmaengine: stm32-dma: set dma_device max_sg

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Date:   Mon, 17 Jan 2022 10:17:40 +0100
From:   Amelie Delaunay <amelie.delaunay@...s.st.com>
To:     Vinod Koul <vkoul@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>
CC:     <dmaengine@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Alain Volmat <alain.volmat@...s.st.com>,
        Amelie Delaunay <amelie.delaunay@...s.st.com>
Subject: [PATCH] dmaengine: stm32-dma: set dma_device max_sg_burst

Some stm32-dma consumers [1] rather use dma_get_slave_caps() to get
max_sg_burst of their DMA channel as dma_get_max_seg_size() is specific to
the DMA controller.
All stm32-dma channels have the same features so, don't need to implement
device_caps ops. Let dma_get_slave_caps() relies on dma_device
configuration.
That's why this patch sets dma_device max_sg_burst to the maximum segment
size, which is the maximum of data items that can be transferred without
software intervention.

[1] https://lore.kernel.org/lkml/20220110103739.118426-1-alain.volmat@foss.st.com/
    "media: stm32: dcmi: create a dma scatterlist based on DMA max_sg_burst value"

Signed-off-by: Amelie Delaunay <amelie.delaunay@...s.st.com>
---
 drivers/dma/stm32-dma.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
index 83a37a6955a3..d2365fab1b7a 100644
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -1389,6 +1389,7 @@ static int stm32_dma_probe(struct platform_device *pdev)
 	dd->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
 	dd->copy_align = DMAENGINE_ALIGN_32_BYTES;
 	dd->max_burst = STM32_DMA_MAX_BURST;
+	dd->max_sg_burst = STM32_DMA_ALIGNED_MAX_DATA_ITEMS;
 	dd->descriptor_reuse = true;
 	dd->dev = &pdev->dev;
 	INIT_LIST_HEAD(&dd->channels);
-- 
2.25.1