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console: Fix pre-console flushing via cfb_console being very slow

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On my A10 OlinuxIno Lime I noticed a huge (5+ seconds) delay coming from
console_init_r. This turns out to be caused by the preconsole buffer flushing
to the cfb_console. The Lime only has a 16 bit memory bus and that is already
heavy used to scan out the 1920x1080 framebuffer.

The problem is that print_pre_console_buffer() was printing the buffer once
character at a time and the cfb_console code then ends up doing a cache-flush
for touched display lines for each character.

This commit fixes this by first building a 0 terminated buffer and then
printing it in one puts() call, avoiding unnecessary cache flushes.

This changes the time for the flush from 5+ seconds to not noticable.

The downside of this approach is that the pre-console buffer needs to fit
on the stack, this is not that much to ask since we are talking about plain
text here. This commit also adjusts the sunxi CONFIG_PRE_CON_BUF_SZ to
actually fit on the stack. Sunxi currently is the only user of the pre-console
code so no other boards need to be adjusted.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
This commit is contained in:
Hans de Goede 2015-05-05 13:13:36 +02:00
parent f9b08fbf11
commit a8552c7c9b
3 changed files with 26 additions and 19 deletions
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3
README
View file

@ -948,6 +948,9 @@ The following options need to be configured:
bytes are output before the console is initialised, the
earlier bytes are discarded.
Note that when printing the buffer a copy is made on the
stack so CONFIG_PRE_CON_BUF_SZ must fit on the stack.
'Sane' compilers will generate smaller code if
CONFIG_PRE_CON_BUF_SZ is a power of 2

40
common/console.c
View file

@ -200,15 +200,15 @@ static void console_putc(int file, const char c)
}
#ifdef CONFIG_PRE_CONSOLE_BUFFER
static void console_putc_noserial(int file, const char c)
static void console_puts_noserial(int file, const char *s)
{
int i;
struct stdio_dev *dev;
for (i = 0; i < cd_count[file]; i++) {
dev = console_devices[file][i];
if (dev->putc != NULL && strcmp(dev->name, "serial") != 0)
dev->putc(dev, c);
if (dev->puts != NULL && strcmp(dev->name, "serial") != 0)
dev->puts(dev, s);
}
}
#endif
@ -251,10 +251,10 @@ static inline void console_putc(int file, const char c)
}
#ifdef CONFIG_PRE_CONSOLE_BUFFER
static inline void console_putc_noserial(int file, const char c)
static inline void console_puts_noserial(int file, const char *s)
{
if (strcmp(stdio_devices[file]->name, "serial") != 0)
stdio_devices[file]->putc(stdio_devices[file], c);
stdio_devices[file]->puts(stdio_devices[file], s);
}
#endif
@ -425,22 +425,26 @@ static void pre_console_puts(const char *s)
static void print_pre_console_buffer(int flushpoint)
{
unsigned long i = 0;
char *buffer = (char *)CONFIG_PRE_CON_BUF_ADDR;
unsigned long in = 0, out = 0;
char *buf_in = (char *)CONFIG_PRE_CON_BUF_ADDR;
char buf_out[CONFIG_PRE_CON_BUF_SZ + 1];
if (gd->precon_buf_idx > CONFIG_PRE_CON_BUF_SZ)
i = gd->precon_buf_idx - CONFIG_PRE_CON_BUF_SZ;
in = gd->precon_buf_idx - CONFIG_PRE_CON_BUF_SZ;
while (i < gd->precon_buf_idx)
switch (flushpoint) {
case PRE_CONSOLE_FLUSHPOINT1_SERIAL:
putc(buffer[CIRC_BUF_IDX(i++)]);
break;
case PRE_CONSOLE_FLUSHPOINT2_EVERYTHING_BUT_SERIAL:
console_putc_noserial(stdout,
buffer[CIRC_BUF_IDX(i++)]);
break;
}
while (in < gd->precon_buf_idx)
buf_out[out++] = buf_in[CIRC_BUF_IDX(in++)];
buf_out[out] = 0;
switch (flushpoint) {
case PRE_CONSOLE_FLUSHPOINT1_SERIAL:
puts(buf_out);
break;
case PRE_CONSOLE_FLUSHPOINT2_EVERYTHING_BUT_SERIAL:
console_puts_noserial(stdout, buf_out);
break;
}
}
#else
static inline void pre_console_putc(const char c) {}

2
include/configs/sunxi-common.h
View file

@ -336,7 +336,7 @@ extern int soft_i2c_gpio_scl;
/* Enable pre-console buffer to get complete log on the VGA console */
#define CONFIG_PRE_CONSOLE_BUFFER
#define CONFIG_PRE_CON_BUF_SZ (1024 * 1024)
#define CONFIG_PRE_CON_BUF_SZ 4096 /* Aprox 2 80*25 screens */
/* Use the room between the end of bootm_size and the framebuffer */
#define CONFIG_PRE_CON_BUF_ADDR 0x4f000000