This is a note to let you know that I've just added the patch titled MIPS: lantiq: dma: add small delay after reset to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mips-lantiq-dma-add-small-delay-after-reset.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 9c42226135d41b022ee8e0b49b4f4c0cd56fc8d8 Author: Aleksander Jan Bajkowski <olek2@xxxxx> Date: Tue Sep 14 23:20:58 2021 +0200 MIPS: lantiq: dma: add small delay after reset [ Upstream commit c12aa581f6d5e80c3c3675ab26a52c2b3b62f76e ] Reading the DMA registers immediately after the reset causes Data Bus Error. Adding a small delay fixes this issue. Signed-off-by: Aleksander Jan Bajkowski <olek2@xxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/mips/lantiq/xway/dma.c b/arch/mips/lantiq/xway/dma.c index cef811755123f..d89a9bcf92c85 100644 --- a/arch/mips/lantiq/xway/dma.c +++ b/arch/mips/lantiq/xway/dma.c @@ -21,6 +21,7 @@ #include <linux/dma-mapping.h> #include <linux/module.h> #include <linux/clk.h> +#include <linux/delay.h> #include <linux/err.h> #include <lantiq_soc.h> @@ -232,6 +233,8 @@ ltq_dma_init(struct platform_device *pdev) clk_enable(clk); ltq_dma_w32_mask(0, DMA_RESET, LTQ_DMA_CTRL); + usleep_range(1, 10); + /* disable all interrupts */ ltq_dma_w32(0, LTQ_DMA_IRNEN);