linux-kernel - Re: [PATCH v4 63/78] drm/vc4: hdmi: Use clk_set_min

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: <CAPY8ntCkuN-cahLd7Ex4awkcUhFVM43nGX4rZCtjRmy-wCyHGQ@mail.gmail.com>
Date:   Tue, 28 Jul 2020 15:57:22 +0100
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Eric Anholt <eric@...olt.net>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        linux-rpi-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>
Subject: Re: [PATCH v4 63/78] drm/vc4: hdmi: Use clk_set_min_rate instead

Hi Maxime

On Wed, 8 Jul 2020 at 18:44, Maxime Ripard <maxime@...no.tech> wrote:
>
> The HSM clock needs to be running at 101% the pixel clock of the HDMI
> controller, however it's shared between the two HDMI controllers, which
> means that if the resolutions are different between the two HDMI
> controllers, and the lowest resolution is on the second (in enable order)
> controller, the first HDMI controller will end up with a smaller than
> expected clock rate.
>
> Since we don't really need an exact frequency there, we can simply change
> the minimum rate we expect instead.
>
> Signed-off-by: Maxime Ripard <maxime@...no.tech>

Reviewed-by: Dave Stevenson <dave.stevenson@...pberrypi.com>

> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index 9f30fab744f2..d99188c90ff9 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -462,7 +462,7 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
>          * pixel clock, but HSM ends up being the limiting factor.
>          */
>         hsm_rate = max_t(unsigned long, 120000000, (pixel_rate / 100) * 101);
> -       ret = clk_set_rate(vc4_hdmi->hsm_clock, hsm_rate);
> +       ret = clk_set_min_rate(vc4_hdmi->hsm_clock, hsm_rate);
>         if (ret) {
>                 DRM_ERROR("Failed to set HSM clock rate: %d\n", ret);
>                 return;
> --
> git-series 0.9.1