linux-kernel - Re: [PATCH v1 2/3] clk: tegra: ignore unused vfir clock shared with uartb

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] [day] [month] [year] [list]

Date:   Mon, 10 Dec 2018 22:41:24 +0100
From:   Marcel Ziswiler <marcel@...wiler.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>
CC:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Michael Turquette <mturquette@...libre.com>,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH v1 2/3] clk: tegra: ignore unused vfir clock shared with uartb



On November 28, 2018 10:24:04 AM GMT+01:00, Thierry Reding <thierry.reding@...il.com> wrote:
>On Thu, Nov 01, 2018 at 10:41:52AM +0200, Peter De Schrijver wrote:
>> On Thu, Nov 01, 2018 at 02:52:29AM +0100, Marcel Ziswiler wrote:
>> > From: Marcel Ziswiler <marcel.ziswiler@...adex.com>
>> > 
>> > As UARTB and VFIR share their clock enable bit it is rather unwise
>for
>> > the kernel to turn off the VFIR one should that be unused (and
>> > potentially vice versa but so far there anyway is no VFIR driver).
>> > 
>> > Without this patch trying to use UARTB with the regular 8250 driver
>> > will freeze as soon as ttyS1 is accessed after boot. Luckily, using
>the
>> > high-speed Tegra serial driver won't exhibit the issue as clocks
>are
>> > dynamically enabled/disabled on every access.
>> > 
>> > This has been reproduced both on Apalis T30 as well as Apalis TK1
>but
>> > may be an issue on all Tegra UARTB's which share the clock enable
>with
>> > VFIR.
>> > 
>> 
>> Ah.. the correct fix for this is to initialize the enable_refcnt
>based on the
>> hw state. This is done in 9619dba8325fce098bbc9ee2911d1b0150fec0c9
>for
>> periph gate clocks, but obviously also applies to normal periph
>clocks.
>
>Hi Marcel,
>
>were you going to send a new version with the alternative fix as
>suggested by Peter?

Yes, sorry. Let me look at that now.

>Thierry