linux-kernel - Re: [RESEND PATCH] amba: Allow pclk to be controlled by power domain

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]

Date:   Tue, 5 Feb 2019 15:58:01 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Russell King <linux@...linux.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Subject: Re: [RESEND PATCH] amba: Allow pclk to be controlled by power domain

On Thu, 31 Jan 2019 at 03:01, Bjorn Andersson
<bjorn.andersson@...aro.org> wrote:
>
> On the Qualcomm SDM845 platform the apb_pclk is controlled as part of
> the QDSS power/clock domain. Handle this by allowing amba to operate
> without direct apb_pclk control, when a powerdomain is attached and no
> clock is described.
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
>
> Resending this separate from the series it was originally part of.
>
>  drivers/amba/bus.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
> index 41b706403ef7..3e13050c6d59 100644
> --- a/drivers/amba/bus.c
> +++ b/drivers/amba/bus.c
> @@ -219,8 +219,13 @@ static int amba_get_enable_pclk(struct amba_device *pcdev)
>         int ret;
>
>         pcdev->pclk = clk_get(&pcdev->dev, "apb_pclk");
> -       if (IS_ERR(pcdev->pclk))
> -               return PTR_ERR(pcdev->pclk);
> +       if (IS_ERR(pcdev->pclk)) {
> +               /* Continue with no clock specified, but pm_domain attached */
> +               if (PTR_ERR(pcdev->pclk) == -ENOENT && pcdev->dev.pm_domain)
> +                       pcdev->pclk = NULL;

This looks fragile to me.

I would prefer to make a do match with DT, to check whether the clock
is needed or not. Moreover, there should be no reason to check for the
->dev.pm_domain, because, if there was an error while doing the
attach, that should already have been reported/propagated.

> +               else
> +                       return PTR_ERR(pcdev->pclk);
> +       }
>
>         ret = clk_prepare_enable(pcdev->pclk);
>         if (ret)
> --
> 2.18.0
>

Kind regards
Uffe