[PATCH RFC 02/12] drm/i2c: tda998x: avoid racy access to mode clock

[Russell King]

Avoid a racy access to the mode clock by storing the current mode clock
during a mode set under the audio mutex.  This allows us to access it
from the audio path in a safe way.

Signed-off-by: Russell King <rmk+kernel at armlinux.org.uk>
---
 drivers/gpu/drm/i2c/tda998x_drv.c | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c 
b/drivers/gpu/drm/i2c/tda998x_drv.c
index 1cc0433ce9d5..ab58a13d815e 100644
--- a/drivers/gpu/drm/i2c/tda998x_drv.c
+++ b/drivers/gpu/drm/i2c/tda998x_drv.c
@@ -47,6 +47,7 @@ struct tda998x_priv {
        u8 vip_cntrl_0;
        u8 vip_cntrl_1;
        u8 vip_cntrl_2;
+       unsigned long tmds_clock;
        struct tda998x_audio_params audio_params;

        struct platform_device *audio_pdev;
@@ -713,8 +714,7 @@ static void tda998x_audio_mute(struct tda998x_priv *priv, 
bool on)

 static int
 tda998x_configure_audio(struct tda998x_priv *priv,
-                       struct tda998x_audio_params *params,
-                       unsigned mode_clock)
+                       struct tda998x_audio_params *params)
 {
        u8 buf[6], clksel_aip, clksel_fs, cts_n, adiv;
        u32 n;
@@ -771,7 +771,7 @@ tda998x_configure_audio(struct tda998x_priv *priv,
         * assume 100MHz requires larger divider.
         */
        adiv = AUDIO_DIV_SERCLK_8;
-       if (mode_clock > 100000)
+       if (priv->tmds_clock > 100000)
                adiv++;                 /* AUDIO_DIV_SERCLK_16 */

        /* S/PDIF asks for a larger divider */
@@ -1064,6 +1064,10 @@ tda998x_encoder_mode_set(struct drm_encoder *encoder,
        /* must be last register set: */
        reg_write(priv, REG_TBG_CNTRL_0, 0);

+       mutex_lock(&priv->audio_mutex);
+
+       priv->tmds_clock = adjusted_mode->clock;
+
        /* Only setup the info frames if the sink is HDMI */
        if (priv->is_hdmi_sink) {
                /* We need to turn HDMI HDCP stuff on to get audio through */
@@ -1074,13 +1078,11 @@ tda998x_encoder_mode_set(struct drm_encoder *encoder,

                tda998x_write_avi(priv, adjusted_mode);

-               mutex_lock(&priv->audio_mutex);
                if (priv->audio_params.format != AFMT_UNUSED)
-                       tda998x_configure_audio(priv,
-                                               &priv->audio_params,
-                                               adjusted_mode->clock);
-               mutex_unlock(&priv->audio_mutex);
+                       tda998x_configure_audio(priv, &priv->audio_params);
        }
+
+       mutex_unlock(&priv->audio_mutex);
 }

 static enum drm_connector_status
@@ -1226,9 +1228,6 @@ static int tda998x_audio_hw_params(struct device *dev, 
void *data,
                .cea = params->cea,
        };

-       if (!priv->encoder.crtc)
-               return -ENODEV;
-
        memcpy(audio.status, params->iec.status,
               min(sizeof(audio.status), sizeof(params->iec.status)));

@@ -1264,9 +1263,7 @@ static int tda998x_audio_hw_params(struct device *dev, 
void *data,
        }

        mutex_lock(&priv->audio_mutex);
-       ret = tda998x_configure_audio(priv,
-                                     &audio,
-                                     priv->encoder.crtc->hwmode.clock);
+       ret = tda998x_configure_audio(priv, &audio);

        if (ret == 0)
                priv->audio_params = audio;
-- 
2.7.4