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36 lines
1.4 KiB
Diff
36 lines
1.4 KiB
Diff
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From 4c1a665b465fa0e9d3369a467fc563ec812a47ce Mon Sep 17 00:00:00 2001
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From: Jonathan Bell <jonathan@raspberrypi.com>
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Date: Fri, 19 Jul 2024 13:07:59 +0100
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Subject: [PATCH 1192/1215] dts: rp1: hobble DMA AXI burst lengths
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Channels 1-2 have a statically configured maximum MSIZE of 8, and
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channels 3-8 have MSIZE set to 4. The DMAC "helpfully" silently
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truncates bursts to the hardware supported maximum, so any FIFO read
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operation with an oversized burst threshold will leave a residue of
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threshold minus MSIZE rows.
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As channel allocation is dynamic, this means every client needs to use a
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maximum of 4 for burst length.
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AXI AWLEN/ARLEN constraints aren't strictly related to MSIZE, except
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that bursts won't be issued that are longer than MSIZE beats. Therefore,
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it's a useful proxy to tell clients of the DMAC the hardware
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limitations.
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Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
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---
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arch/arm64/boot/dts/broadcom/rp1.dtsi | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/arch/arm64/boot/dts/broadcom/rp1.dtsi
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+++ b/arch/arm64/boot/dts/broadcom/rp1.dtsi
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@@ -1064,7 +1064,7 @@
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snps,data-width = <4>; // (8 << 4) == 128 bits
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snps,block-size = <0x40000 0x40000 0x40000 0x40000 0x40000 0x40000 0x40000 0x40000>;
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snps,priority = <0 1 2 3 4 5 6 7>;
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- snps,axi-max-burst-len = <8>;
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+ snps,axi-max-burst-len = <4>;
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status = "disabled";
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};
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