Re: [PATCH 2/3] firmware: arm_scmi: Fix freq/power truncation in the perf protocol
From: Sibi Sankar
Date: Thu Nov 30 2023 - 14:32:42 EST
On 11/30/23 21:55, Cristian Marussi wrote:
On Thu, Nov 30, 2023 at 01:56:56PM +0000, Sudeep Holla wrote:
On Thu, Nov 30, 2023 at 12:49:42PM +0000, Cristian Marussi wrote:
On Thu, Nov 30, 2023 at 12:05:06PM +0000, Sudeep Holla wrote:
On Wed, Nov 29, 2023 at 12:27:47PM +0530, Sibi Sankar wrote:
Fix frequency and power truncation seen in the performance protocol by
casting it with the correct type.
While I always remembered to handle this when reviewing the spec, seem to
have forgotten when it came to handling in the implementation :(. Thanks
for spotting this.
However I don't like the ugly type casting. I think we can do better. Also
looking at the code around the recently added level index mode, I think we
can simplify things like below patch.
Cristian,
What do you think ?
Hi
the cleanup seems nice in general to compact the mult_factor multipliers
in one place, and regarding addressing the problem of truncation without
the need of the explicit casting, should not be enough to change to
additionally also change mult_factor to be an u64 ?
I started exactly with that, but when I completed the patch, there was no
explicit need for it, so dropped it again. I can bump mult_factor to be
u64 but do you see any other place that would need it apart from having
single statement that does multiplication and assignment ? I am exploiting
the conditional based on level_indexing_mode here but I agree it may help
in backporting if I make mult_factor u64.
Ah right
freq *= dom->multi_fact;
does the trick..but cannot this by itself (under unplausibl conds)
overflow and does not fit into a u32 mult_factor ?
dom_info->mult_factor =
(dom_info->sustained_freq_khz * 1000UL)
wouldn't having the 1000UL ensure that we don't truncate though?
Anyway will drop the patch when I re-spin the series.
-Sibi
/ dom_info->sustained_perf_level;
Thanks,
Cristian