mail archive of the barebox mailing list
 help / color / mirror / Atom feed
* [PATCH master] ARM: sync_caches_for_execution: don't flush disabled data cache
@ 2022-09-01 10:41 Ahmad Fatoum
  2022-09-13  8:39 ` Sascha Hauer
  0 siblings, 1 reply; 2+ messages in thread
From: Ahmad Fatoum @ 2022-09-01 10:41 UTC (permalink / raw)
  To: barebox; +Cc: Ahmad Fatoum

We unconditionally clean and then invalidate D-cache entries in
sync_caches_for_execution by calling arm_early_mmu_cache_flush().

The function afterwards takes care to invalidate the I-cache.

This misbehaves though when the D-Cache contains stale dirty
entries for currently executing code. Most boards avoid this
pitfall, because barebox_arm_entry calls
arm_early_mmu_cache_invalidate() and sync_caches_for_execution()
is only called afterwards. But for some boards,
relocate_to_current_adr() is called before barebox_arm_entry and
various board code works around this by calling
arm_early_mmu_cache_invalidate() first.

Make this unnecessary by not flushing the data cache when it's disabled
and instead only invalidate the I-Cache.

This fixes a hang observed on a serial-booted i.MX6Q rev 1.5
executing relocate_to_current_adr() -> sync_caches_for_execution()
from On-Chip SRAM.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 arch/arm/cpu/common.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/cpu/common.c b/arch/arm/cpu/common.c
index 8cfcc8f6ce7a..5ccacf204751 100644
--- a/arch/arm/cpu/common.c
+++ b/arch/arm/cpu/common.c
@@ -23,6 +23,12 @@
  */
 void sync_caches_for_execution(void)
 {
+	/* if caches are disabled, don't do data cache maintenance */
+	if (!(get_cr() & CR_C)) {
+		icache_invalidate();
+		return;
+	}
+
 	/*
 	 * Despite the name arm_early_mmu_cache_flush not only flushes the
 	 * data cache, but also invalidates the instruction cache.
-- 
2.30.2




^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH master] ARM: sync_caches_for_execution: don't flush disabled data cache
  2022-09-01 10:41 [PATCH master] ARM: sync_caches_for_execution: don't flush disabled data cache Ahmad Fatoum
@ 2022-09-13  8:39 ` Sascha Hauer
  0 siblings, 0 replies; 2+ messages in thread
From: Sascha Hauer @ 2022-09-13  8:39 UTC (permalink / raw)
  To: Ahmad Fatoum; +Cc: barebox

On Thu, Sep 01, 2022 at 12:41:36PM +0200, Ahmad Fatoum wrote:
> We unconditionally clean and then invalidate D-cache entries in
> sync_caches_for_execution by calling arm_early_mmu_cache_flush().
> 
> The function afterwards takes care to invalidate the I-cache.
> 
> This misbehaves though when the D-Cache contains stale dirty
> entries for currently executing code. Most boards avoid this
> pitfall, because barebox_arm_entry calls
> arm_early_mmu_cache_invalidate() and sync_caches_for_execution()
> is only called afterwards. But for some boards,
> relocate_to_current_adr() is called before barebox_arm_entry and
> various board code works around this by calling
> arm_early_mmu_cache_invalidate() first.
> 
> Make this unnecessary by not flushing the data cache when it's disabled
> and instead only invalidate the I-Cache.
> 
> This fixes a hang observed on a serial-booted i.MX6Q rev 1.5
> executing relocate_to_current_adr() -> sync_caches_for_execution()
> from On-Chip SRAM.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  arch/arm/cpu/common.c | 6 ++++++
>  1 file changed, 6 insertions(+)

Applied, thanks

Sascha

> 
> diff --git a/arch/arm/cpu/common.c b/arch/arm/cpu/common.c
> index 8cfcc8f6ce7a..5ccacf204751 100644
> --- a/arch/arm/cpu/common.c
> +++ b/arch/arm/cpu/common.c
> @@ -23,6 +23,12 @@
>   */
>  void sync_caches_for_execution(void)
>  {
> +	/* if caches are disabled, don't do data cache maintenance */
> +	if (!(get_cr() & CR_C)) {
> +		icache_invalidate();
> +		return;
> +	}
> +
>  	/*
>  	 * Despite the name arm_early_mmu_cache_flush not only flushes the
>  	 * data cache, but also invalidates the instruction cache.
> -- 
> 2.30.2
> 
> 
> 

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |



^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2022-09-13  8:42 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-09-01 10:41 [PATCH master] ARM: sync_caches_for_execution: don't flush disabled data cache Ahmad Fatoum
2022-09-13  8:39 ` Sascha Hauer

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox