linux-kernel - Re: [PATCH v3 055/105] drm/vc4: hvs: Introduce a function to get the assigned FIFO

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Date:   Wed, 27 May 2020 12:40:02 -0700
From:   Eric Anholt <eric@...olt.net>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        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, linux-kernel@...r.kernel.org,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>
Subject: Re: [PATCH v3 055/105] drm/vc4: hvs: Introduce a function to get the
 assigned FIFO

On Wed, May 27, 2020 at 8:50 AM Maxime Ripard <maxime@...no.tech> wrote:
>
> At boot time, if we detect that a pixelvalve has been enabled, we need to
> be able to retrieve the HVS channel it has been assigned to so that we can
> disable that channel too. Let's create that function that returns the FIFO
> or an error from a given output.
>
> Signed-off-by: Maxime Ripard <maxime@...no.tech>
> ---

> +int vc4_hvs_get_fifo_from_output(struct drm_device *dev, unsigned int output)
> +{
> +       struct vc4_dev *vc4 = to_vc4_dev(dev);
> +       u32 reg;
> +       int ret;
> +
> +       switch (output) {
> +       case 0:
> +               return 0;
> +
> +       case 1:
> +               return 1;
> +
> +       case 2:
> +               reg = HVS_READ(SCALER_DISPECTRL);
> +               ret = FIELD_GET(SCALER_DISPECTRL_DSP2_MUX_MASK, reg);
> +               if (ret == 0)
> +                       return 2;
> +
> +               return 0;
> +
> +       case 3:
> +               reg = HVS_READ(SCALER_DISPCTRL);
> +               ret = FIELD_GET(SCALER_DISPCTRL_DSP3_MUX_MASK, reg);
> +               if (ret == 3)
> +                       return -EPIPE;
> +
> +               return ret;
> +
> +       case 4:
> +               reg = HVS_READ(SCALER_DISPEOLN);
> +               ret = FIELD_GET(SCALER_DISPEOLN_DSP4_MUX_MASK, reg);
> +               if (ret == 3)
> +                       return -EPIPE;
> +
> +               return ret;
> +
> +       case 5:
> +               reg = HVS_READ(SCALER_DISPDITHER);
> +               ret = FIELD_GET(SCALER_DISPDITHER_DSP5_MUX_MASK, reg);
> +               if (ret == 3)
> +                       return -EPIPE;

Oh, FIELD_GET is new to me.  Looks like we should replace
VC4_GET_FIELD usage with just using that header, and also
VC4_SET_FIELD with WARN_ON(!FIELD_FIT()); FIELD_PREP.

Could you follow up with that?  Other than that, 54-67 r-b.