linux-kernel - Re: [PATCH v2] soc: qcom: do not disable the iface clock in probe

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <5422E390.9060802@linaro.org>
Date:	Wed, 24 Sep 2014 16:30:24 +0100
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Kevin Hilman <khilman@...nel.org>
CC:	arm@...nel.org, agross@...eaurora.org, galak@...eaurora.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] soc: qcom: do not disable the iface clock in probe



On 24/09/14 16:22, Kevin Hilman wrote:
> Srinivas Kandagatla <srinivas.kandagatla@...aro.org> writes:
>
>> since commit 31964ffebbb9 ("tty: serial: msm: Remove direct access to GSBI")'
>> serial hangs if earlyprintk are enabled.
>>
>> This hang is noticed only when the GSBI driver is probed and all the
>> earlyprintks before gsbi probe are seen on the console.
>> The reason why it hangs is because GSBI driver disables hclk in its
>> probe function without realizing that the serial IP might be in use by
>> a bootconsole. As gsbi driver disables the clock in probe the
>> bootconsole locks up.
>
>> Turning off hclk's could be dangerous if there are system components
>> like earlyprintk using the hclk.
>
> This seems rather fragile.  Isn't the right fix for these other
> components to use the clk api to ensure the clock does not get enabled?
Here we are depending on the bootloader to setup the clocks.

Am not sure if we can really use clk apis at that early stage of bootstrap.

--srini



>
> Kevin
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/