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authorTomoya MORINAGA <tomoya.rohm@gmail.com>2011-11-11 05:55:27 +0400
committerGreg Kroah-Hartman <gregkh@suse.de>2011-11-16 00:13:43 +0400
commit90f04c2926cfb5bf74533b0a7766bc896f6a0c0e (patch)
tree36f4a4e1c0381ce5ac5217e35e437e43c529fc27 /Documentation/serial
parent604fdb75094a7367e1794fd0f62183380364ce13 (diff)
downloadlinux-90f04c2926cfb5bf74533b0a7766bc896f6a0c0e.tar.xz
pch_uart: Fix DMA resource leak issue
Changing UART mode PIO->DMA->PIO->DMA like below, pch_uart driver can't get DMA channel resource. setserial /dev/ttyPCH0 ^low_latency setserial /dev/ttyPCH0 low_latency CAUSE: Changing mode using setserial command, ".startup" function which gets DMA channel is called before ".verify_port" function which sets dma-flag(use_dma/use_dma_flag) as 1. PIO->DMA .startup: Since dma-flag is 0, DMA channel is not requested. .verify_port: dma-flag is set as 1. .shutdown: N/A DMA->PIO .startup: Since dma-flag is 1, DMA channel is requested. .verify_port: dma-flag is set as 0. .shutdown: Since dma-flag is 0, DMA channel is not released. This means DMA channel resource leak occurs. Next time, this driver can't get DMA channel resource forever. MODIFICATION: Currently, when release DMA channel resource, this driver checks dma-flag. However, this specification occurs the above issue. This driver must check whether dma_request_channel is executed or not. The values are saved in private data variable "chan_tx/chan_tx". These variables mean if the value is NULL, DMA channel is not requested, if not NULL, DMA channel is requested. This patch fixes the issue. Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com> Acked-by: Alan Cox <alan@linux.intel.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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