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author | Tomoya MORINAGA <tomoya.rohm@gmail.com> | 2011-11-11 05:55:27 +0400 |
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committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-11-16 00:13:43 +0400 |
commit | 90f04c2926cfb5bf74533b0a7766bc896f6a0c0e (patch) | |
tree | 36f4a4e1c0381ce5ac5217e35e437e43c529fc27 /Documentation/serial | |
parent | 604fdb75094a7367e1794fd0f62183380364ce13 (diff) | |
download | linux-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>
Diffstat (limited to 'Documentation/serial')
0 files changed, 0 insertions, 0 deletions