dmaengine: of_dma: approximate an average distribution (20ea6be6) · Commits · 戴 / test

Currently the following DT description would result in dmac0 always being tried first and dmac1 second if dmac0 was unavailable. This results in heavier use of dmac0 then of dmac1. This patch adds an approximate average distribution over the two nodes lessening the load of anyone of them. i2c6: i2c@e60b0000 { ... dmas = <&dmac0 0x77>, <&dmac0 0x78>, <&dmac1 0x77>, <&dmac1 0x78>; dma-names = "tx", "rx", "tx", "rx"; ... }; Signed-off-by:

Arnd Bergmann <arnd@arndb.de> Signed-off-by:

Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se> Suggested-by:

Arnd Bergmann <arnd@arndb.de> Signed-off-by:

Vinod Koul <vinod.koul@intel.com>

drivers/dma/of-dma.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -240,8 +240,9 @@ struct dma_chan of_dma_request_slave_channel(struct device_node np,
		struct of_phandle_args dma_spec;
		struct of_dma *ofdma;
		struct dma_chan *chan;
		int count, i;
		int count, i, start;
		int ret_no_channel = -ENODEV;
		static atomic_t last_index;

		if (!np \|\| !name) {
		pr_err("%s: not enough information provided\n", __func__);
		@@ -259,8 +260,15 @@ struct dma_chan of_dma_request_slave_channel(struct device_node np,
		return ERR_PTR(-ENODEV);
		}

		/*
		* approximate an average distribution across multiple
		* entries with the same name
		*/
		start = atomic_inc_return(&last_index);
		for (i = 0; i < count; i++) {
		if (of_dma_match_channel(np, name, i, &dma_spec))
		if (of_dma_match_channel(np, name,
		(i + start) % count,
		&dma_spec))
		continue;

		mutex_lock(&of_dma_lock);

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