4.19-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 7ab57b76ebf632bf2231ccabe26bea33868118c6 ]
We increase the default limit for buffer memory allocation by a factor of 10 to 640K to prevent data loss when using fast serial interfaces.
For example when using RS485 without flow-control at speeds of 1Mbit/s an upwards we've run into problems such as applications being too slow to read out this buffer (on embedded devices based on imx53 or imx6).
If you want to write transmitted data to a slow SD card and thus have realtime requirements, this limit can become a problem.
That shouldn't be the case and 640K buffers fix such problems for us.
This value is a maximum limit for allocation only. It has no effect on systems that currently run fine. When transmission is slow enough applications and hardware can keep up and increasing this limit doesn't change anything.
It only _allows_ to allocate more than 2*64K in cases we currently fail to allocate memory despite having some.
Signed-off-by: Manfred Schlaegl manfred.schlaegl@ginzinger.com Signed-off-by: Martin Kepplinger martin.kepplinger@ginzinger.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/tty_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index ae3ce330200e..ee3aa57bc0e7 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -26,7 +26,7 @@ * Byte threshold to limit memory consumption for flip buffers. * The actual memory limit is > 2x this amount. */ -#define TTYB_DEFAULT_MEM_LIMIT 65536 +#define TTYB_DEFAULT_MEM_LIMIT (640 * 1024UL)
/* * We default to dicing tty buffer allocations to this many characters