Messages in this thread Patch in this message | | | Date | Tue, 22 Nov 2011 16:23:26 -0800 | From | Greg KH <> | Subject | [19/53] pch_uart: Fix DMA resource leak issue |
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3.0-stable review patch. If anyone has any objections, please let me know.
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From: Tomoya MORINAGA <tomoya.rohm@gmail.com>
commit 90f04c2926cfb5bf74533b0a7766bc896f6a0c0e upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/tty/serial/pch_uart.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/tty/serial/pch_uart.c +++ b/drivers/tty/serial/pch_uart.c @@ -625,6 +625,7 @@ static void pch_request_dma(struct uart_ dev_err(priv->port.dev, "%s:dma_request_channel FAILS(Rx)\n", __func__); dma_release_channel(priv->chan_tx); + priv->chan_tx = NULL; return; } @@ -1212,8 +1213,7 @@ static void pch_uart_shutdown(struct uar dev_err(priv->port.dev, "pch_uart_hal_set_fifo Failed(ret=%d)\n", ret); - if (priv->use_dma_flag) - pch_free_dma(port); + pch_free_dma(port); free_irq(priv->port.irq, priv); }
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