linux-kernel - Re: [PATCH v3 4/8] clk: renesas: rzg2l-cpg: Add support for MSTOP in clock enable/disable API

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMuHMdXOTiNcuGn4JSEAN3j=X51imvitgKpzSouwzjycJObbog@mail.gmail.com>
Date: Thu, 5 Jun 2025 11:35:16 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Claudiu <claudiu.beznea@...on.dev>
Cc: mturquette@...libre.com, sboyd@...nel.org, robh@...nel.org, 
	krzk+dt@...nel.org, conor+dt@...nel.org, magnus.damm@...il.com, 
	linux-renesas-soc@...r.kernel.org, linux-clk@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH v3 4/8] clk: renesas: rzg2l-cpg: Add support for MSTOP in
 clock enable/disable API

On Tue, 27 May 2025 at 13:24, Claudiu <claudiu.beznea@...on.dev> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>
> The RZ/{G2L, V2L, G3S} CPG versions support a feature called MSTOP. Each
> module has one or more MSTOP bits associated with it, and these bits need
> to be configured along with the module clocks. Setting the MSTOP bits
> switches the module between normal and standby states.
>
> Previously, MSTOP support was abstracted through power domains
> (struct generic_pm_domain::{power_on, power_off} APIs). With this
> abstraction, the order of setting the MSTOP and CLKON bits was as follows:
>
> Previous Order:
> A/ Switching to Normal State (e.g., during probe):
> 1/ Clear module MSTOP bit
> 2/ Set module CLKON bit
>
> B/ Switching to Standby State (e.g., during remove):
> 1/ Clear CLKON bit
> 2/ Set MSTOP bit
>
> However, in some cases (when the clock is disabled through devres), the
> order may have been (due to the issue described in link section):
>
> 1/ Set MSTOP bit
> 2/ Clear CLKON bit
>
> Recently, the hardware team has suggested that the correct order to set
> the MSTOP and CLKON bits is:
>
> Updated Order:
> A/ Switching to Normal State (e.g., during probe):
> 1/ Set CLKON bit
> 2/ Clear MSTOP bit
>
> B/ Switching to Standby State (e.g., during remove):
> 1/ Set MSTOP bit
> 2/ Clear CLKON bit
>
> To prevent future issues due to incorrect ordering, the MSTOP setup has
> now been implemented in rzg2l_mod_clock_endisable(), ensuring compliance
> with the sequence suggested in Figure 41.5: Module Standby Mode Procedure
> from the RZ/G3S HW manual, Rev1.10.
>
> Additionally, since multiple clocks of a single module may be mapped to a
> single MSTOP bit, MSTOP setup is reference-counted.
>
> Furthermore, as all modules start in the normal state after reset, if the
> module clocks are disabled, the module state is switched to standby. This
> prevents keeping the module in an invalid state, as recommended by the
> hardware team.
>
> Link: https://lore.kernel.org/all/20250215130849.227812-1-claudiu.beznea.uj@bp.renesas.com/
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> ---
>
> Changes in v3:
> - s/for_each_mstp_clk/for_each_mod_clock/g
> - do not add clock to its own shared_mstop_clk[] array if it doesn't share
>   the mstop
> - update the shared_mstop_clks[] before priv->clks[] array is populated
>   when registering a clock; this simplifies the logic in
>   rzg2l_mod_clock_update_shared_mstop_clks()
> - in rzg2l_mod_clock_module_set_state():
> -- in case the requested module state is normal update the register
>    only when the mstop->usecnt is zero
> -- in case the requested module state is standby and the clock don't share
>    the mstop, check explictily if it is critical and increment local variable
>    "criticals" if so; this is necessary now as the clock is not preset in
>    shared_mstop_clks[] array if it doesn't share the mstop

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
i.e. will queue in renesas-clk for v6.17.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds