Re: [PATCH 0/2] m68k: Add DMA timers support for M5441x

[Jean-Michel Hautbois <jeanmichel.hautbois@yoseli.org>]

Hi !

On 02/12/2024 10:29, Jean-Michel Hautbois wrote:
> This patch series adds support for DMA timers for the M5441x coldfire
> family. The aim is to provide finer scheduler resolution and support for
> high-resolution timers.
> 
> The first patch fixes the clocks and a typo. The second one is the
> timers support addition. As there is no device tree, I did not use
> TIMER_OF_DECLARE().
> 
> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@yoseli.org>
> ---
> Jean-Michel Hautbois (2):
>        m68k: coldfire: Use proper clock rate for timers
>        m68k: m5441x: Add DMA timer support
> 
>   MAINTAINERS                         |   6 +
>   arch/m68k/coldfire/m5441x.c         |  20 +--
>   arch/m68k/include/asm/m5441xsim.h   |  18 +++
>   drivers/clocksource/Kconfig         |   9 ++
>   drivers/clocksource/Makefile        |   1 +
>   drivers/clocksource/mcf_dma_timer.c | 240 ++++++++++++++++++++++++++++++++++++
>   6 files changed, 284 insertions(+), 10 deletions(-)
> ---
> base-commit: e3f432391d55ec21274bd16a04659b4a24678535
> change-id: 20241202-m5441x_dma_tmr-d969f4cc30a8
> 
> Best regards,

Gentle ping, as I don't know if anyone is interested by this patch :-) ?

I think it makes coldfire really better but it certainly has issues !

On my kernel, m54418, I observed a few things.

First, when launching cyclictest I get sometimes a bad irq handle:
[  720.442175] irq 24, desc: 6b62142b, depth: 1, count: 0, unhandled: 0
[  720.442329] ->handle_irq():  e4232a91, handle_bad_irq+0x0/0x1e6
[  720.442498] ->irq_data.chip(): 66a62b77, 0x4183e868
[  720.442613] ->action(): 00000000
[  720.442667] unexpected IRQ trap at vector 18

These IRQ numbers are a bit weird, I suppose it is a spurious IRQ, but 
not sure ?

Next, cyclictest might experience *very* long delay if the CPU is very 
busy and a ping flood burst comes in:
# cyclictest -m -p 98 --secaligned
WARN: stat /dev/cpu_dma_latency failed: No such file or directory
policy: fifo: loadavg: 2.24 1.94 1.03 1/127 252

T: 0 (  251) P:98 I:1000 C:  53113 Min:    116 Act:  327 Avg:  209 Max: 
  60353

Any review would be appreciated, at least to know if it is totally off 
or not that bad and needs a few fixes ?

Thanks,
JM