Re: [PATCH 03/15] drm/vc4: hdmi: Fix register offset with longer CEC messages

[Dave Stevenson]

Hi Dom & Maxime

On Thu, 10 Dec 2020 at 13:46, Maxime Ripard <maxime@xxxxxxxxxx> wrote:
>
> From: Dom Cobley <popcornmix@xxxxxxxxx>
>
> The code prior to 311e305fdb4e ("drm/vc4: hdmi: Implement a register
> layout abstraction") was relying on the fact that the register offset
> was incremented by 4 for each readl call. That worked since the register
> width is 4 bytes.
>
> However, since that commit the HDMI_READ macro is now taking an enum,
> and the offset doesn't increment by 4 but 1 now. Divide the index by 4
> to fix this.
>
> Fixes: 311e305fdb4e ("drm/vc4: hdmi: Implement a register layout abstraction")
> Signed-off-by: Dom Cobley <popcornmix@xxxxxxxxx>
> Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx>

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

> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index 3df1747dd917..28b78ea885ea 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -1434,13 +1434,20 @@ static irqreturn_t vc4_cec_irq_handler_thread(int irq, void *priv)
>
>  static void vc4_cec_read_msg(struct vc4_hdmi *vc4_hdmi, u32 cntrl1)
>  {
> +       struct drm_device *dev = vc4_hdmi->connector.dev;
>         struct cec_msg *msg = &vc4_hdmi->cec_rx_msg;
>         unsigned int i;
>
>         msg->len = 1 + ((cntrl1 & VC4_HDMI_CEC_REC_WRD_CNT_MASK) >>
>                                         VC4_HDMI_CEC_REC_WRD_CNT_SHIFT);
> +
> +       if (msg->len > 16) {
> +               drm_err(dev, "Attempting to read too much data (%d)\n", msg->len);
> +               return;
> +       }
> +
>         for (i = 0; i < msg->len; i += 4) {
> -               u32 val = HDMI_READ(HDMI_CEC_RX_DATA_1 + i);
> +               u32 val = HDMI_READ(HDMI_CEC_RX_DATA_1 + (i >> 2));
>
>                 msg->msg[i] = val & 0xff;
>                 msg->msg[i + 1] = (val >> 8) & 0xff;
> @@ -1533,11 +1540,17 @@ static int vc4_hdmi_cec_adap_transmit(struct cec_adapter *adap, u8 attempts,
>                                       u32 signal_free_time, struct cec_msg *msg)
>  {
>         struct vc4_hdmi *vc4_hdmi = cec_get_drvdata(adap);
> +       struct drm_device *dev = vc4_hdmi->connector.dev;
>         u32 val;
>         unsigned int i;
>
> +       if (msg->len > 16) {
> +               drm_err(dev, "Attempting to transmit too much data (%d)\n", msg->len);
> +               return -ENOMEM;
> +       }
> +
>         for (i = 0; i < msg->len; i += 4)
> -               HDMI_WRITE(HDMI_CEC_TX_DATA_1 + i,
> +               HDMI_WRITE(HDMI_CEC_TX_DATA_1 + (i >> 2),
>                            (msg->msg[i]) |
>                            (msg->msg[i + 1] << 8) |
>                            (msg->msg[i + 2] << 16) |
> --
> 2.28.0
>