projects / thirdparty / kernel / stable-queue.git / blame
| Commit | Line | Data |
|---|---|---|
| ba172962 SL |
1 | From 36ebe625e05239c105f8c3d6f0c00305314e41a2 Mon Sep 17 00:00:00 2001 |
| 2 | From: Manfred Schlaegl <manfred.schlaegl@ginzinger.com> | |
| 3 | Date: Mon, 28 Jan 2019 19:01:10 +0100 | |
| 4 | Subject: tty: increase the default flip buffer limit to 2*640K | |
| 5 | ||
| 6 | [ Upstream commit 7ab57b76ebf632bf2231ccabe26bea33868118c6 ] | |
| 7 | ||
| 8 | We increase the default limit for buffer memory allocation by a factor of | |
| 9 | 10 to 640K to prevent data loss when using fast serial interfaces. | |
| 10 | ||
| 11 | For example when using RS485 without flow-control at speeds of 1Mbit/s | |
| 12 | an upwards we've run into problems such as applications being too slow | |
| 13 | to read out this buffer (on embedded devices based on imx53 or imx6). | |
| 14 | ||
| 15 | If you want to write transmitted data to a slow SD card and thus have | |
| 16 | realtime requirements, this limit can become a problem. | |
| 17 | ||
| 18 | That shouldn't be the case and 640K buffers fix such problems for us. | |
| 19 | ||
| 20 | This value is a maximum limit for allocation only. It has no effect | |
| 21 | on systems that currently run fine. When transmission is slow enough | |
| 22 | applications and hardware can keep up and increasing this limit | |
| 23 | doesn't change anything. | |
| 24 | ||
| 25 | It only _allows_ to allocate more than 2*64K in cases we currently fail to | |
| 26 | allocate memory despite having some. | |
| 27 | ||
| 28 | Signed-off-by: Manfred Schlaegl <manfred.schlaegl@ginzinger.com> | |
| 29 | Signed-off-by: Martin Kepplinger <martin.kepplinger@ginzinger.com> | |
| 30 | Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> | |
| 31 | Signed-off-by: Sasha Levin <sashal@kernel.org> | |
| 32 | --- | |
| 33 | drivers/tty/tty_buffer.c | 2 +- | |
| 34 | 1 file changed, 1 insertion(+), 1 deletion(-) | |
| 35 | ||
| 36 | diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c | |
| 37 | index ae3ce330200e..ee3aa57bc0e7 100644 | |
| 38 | --- a/drivers/tty/tty_buffer.c | |
| 39 | +++ b/drivers/tty/tty_buffer.c | |
| 40 | @@ -26,7 +26,7 @@ | |
| 41 | * Byte threshold to limit memory consumption for flip buffers. | |
| 42 | * The actual memory limit is > 2x this amount. | |
| 43 | */ | |
| 44 | -#define TTYB_DEFAULT_MEM_LIMIT 65536 | |
| 45 | +#define TTYB_DEFAULT_MEM_LIMIT (640 * 1024UL) | |
| 46 | ||
| 47 | /* | |
| 48 | * We default to dicing tty buffer allocations to this many characters | |
| 49 | -- | |
| 50 | 2.19.1 | |
| 51 |