drm/vc4: hdmi: Fix register offset with longer CEC messages

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")
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Dom Cobley <popcornmix@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Tested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Link: https://patchwork.freedesktop.org/patch/msgid/20210111142309.193441-4-maxime@cerno.tech
(cherry picked from commit e9c9481f373eb7344f9e973eb28fc6e9d0f46485)
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 94be67a..184e1f0 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1444,13 +1444,20 @@ 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;
@@ -1543,11 +1550,17 @@ 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) |