[PATCH] Disable timer check in file loading

[Heinrich Schuchardt]

On 7/8/21 10:22 AM, Michael Chang wrote:
> The u-boot efi console service registers a timer to poll the keyboard
> input in every 50ns. In the efi block io service, this timer is

The event is triggered every 5000 ns not 50 ns. See
lib/efi_loader/efi_console.c:1309. The SetTimer() parameter is in
multiples of 100 ns. UEFI spec 2.9 has this sentence:
"TimerRelative: The event is to be signaled in TriggerTime 100ns units."

> evaluated on each block read, and since the timer interval is much less
> than the time needed to reading out a block (32kB) from the disk, the
> keyboard polling is therefore in the wake of each block read.
>
> Unfortunately USB keyboard spends too much time in polling. In my test
> usb_kbd_poll_for_event costs 40ms in usb_kbd_testc() to test if a

I can't imagine that Linux is that slow. Why is U-Boot so slow? Please,
try to fix that code.

> character is in the queue. In combination with the number of blocks to
> be read from the disk, the extra amound of time delayed could be around
> 30 seconds to load linux and initrd.
>
> For that matters, the timer check is disabled in file loading to speed
> it up. The consequence would be losing the keystroke during the time
> file is loading, but that is acceptable IMHO.

Disabling would mean that programs like iPXE cannot react to keyboard
input to interrupt a file transfer.

Best regards

Heinrich

>
> Downstream bug reference:
> https://bugzilla.suse.com/show_bug.cgi?id=1171222
>
> Signed-off-by: Michael Chang <mchang at suse.com>
> ---
>   lib/efi_loader/efi_disk.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/efi_loader/efi_disk.c b/lib/efi_loader/efi_disk.c
> index 307d5d759b..d090110b06 100644
> --- a/lib/efi_loader/efi_disk.c
> +++ b/lib/efi_loader/efi_disk.c
> @@ -15,6 +15,7 @@
>   #include <log.h>
>   #include <part.h>
>   #include <malloc.h>
> +#include <watchdog.h>
>
>   struct efi_system_partition efi_system_partition;
>
> @@ -103,8 +104,7 @@ static efi_status_t efi_disk_rw_blocks(struct efi_block_io *this,
>   	else
>   		n = blk_dwrite(desc, lba, blocks, buffer);
>
> -	/* We don't do interrupts, so check for timers cooperatively */
> -	efi_timer_check();
> +	WATCHDOG_RESET();
>
>   	EFI_PRINT("n=%lx blocks=%x\n", n, blocks);
>
>