mirror of
https://github.com/openwrt/openwrt.git
synced 2024-12-25 16:31:13 +00:00
42 lines
1.7 KiB
Diff
42 lines
1.7 KiB
Diff
|
From b35cdbcc3966e61b87d1e89f3ac8e172f15be4ff Mon Sep 17 00:00:00 2001
|
||
|
From: Phil Elwell <phil@raspberrypi.com>
|
||
|
Date: Thu, 14 Mar 2024 21:32:32 +0000
|
||
|
Subject: [PATCH 0967/1085] dmaengine: dw-axi-dmac: Fix a non-atomic update
|
||
|
|
||
|
dw_axi_dma_interrupt disables interrupts for the duration of the channel
|
||
|
handling. It does so by clearing a bit in the DMA_CFG register - an
|
||
|
action that involves a read-modify-write. That in itself would be safe
|
||
|
because there will be no further interrupts, hence no reentrancy, were
|
||
|
it the only bit of code accessing that register.
|
||
|
|
||
|
The only neighbour of INT_EN is DMAC_EN - the main enable for the block.
|
||
|
That's not the sort of thing you would expect to be modified during the
|
||
|
normal course of operation, but bizarrely it is set at the start of the
|
||
|
transfer of every block, in axi_chan_block_xfer_star, by a call to
|
||
|
axi_dma_enable. This can lead to INT_EN being accidentally cleared,
|
||
|
which causes all DMA transfers to time out.
|
||
|
|
||
|
One might think that the enabling was being delayed until the first
|
||
|
transfer, but the probe function calls axi_dma_resume which in turn
|
||
|
calls axi_dma_enable, so that isn't the case.
|
||
|
|
||
|
Fix the atomicity problem by removing the spurious call to
|
||
|
axi_dma_enable.
|
||
|
|
||
|
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
|
||
|
---
|
||
|
drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c | 2 --
|
||
|
1 file changed, 2 deletions(-)
|
||
|
|
||
|
--- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
|
||
|
+++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
|
||
|
@@ -465,8 +465,6 @@ static void axi_chan_block_xfer_start(st
|
||
|
return;
|
||
|
}
|
||
|
|
||
|
- axi_dma_enable(chan->chip);
|
||
|
-
|
||
|
config.dst_multblk_type = DWAXIDMAC_MBLK_TYPE_LL;
|
||
|
config.src_multblk_type = DWAXIDMAC_MBLK_TYPE_LL;
|
||
|
config.tt_fc = DWAXIDMAC_TT_FC_MEM_TO_MEM_DMAC;
|