linux-kernel - Re: [PATCH] drm/rockchip: cdn-dp: send audio infoframe to sink

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Message-ID: <20170717202300.c2r7ypclqbwvqbzq@art_vandelay>
Date:   Mon, 17 Jul 2017 16:23:00 -0400
From:   Sean Paul <seanpaul@...omium.org>
To:     Chris Zhong <zyw@...k-chips.com>
Cc:     linux-rockchip@...ts.infradead.org, seanpaul@...omium.org,
        dianders@...omium.org, briannorris@...omium.org,
        Mark Yao <mark.yao@...k-chips.com>,
        David Airlie <airlied@...ux.ie>,
        Heiko Stuebner <heiko@...ech.de>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/rockchip: cdn-dp: send audio infoframe to sink

On Sat, Jul 15, 2017 at 07:00:18PM +0800, Chris Zhong wrote:
> Some DP/HDMI sink need to receive the audio infoframe to play sound,
> especially some multi-channel AV receiver, they need the
> channel_allocation from infoframe to config the speakers. Send the
> audio infoframe via SDP will make them work properly.
> 
> Signed-off-by: Chris Zhong <zyw@...k-chips.com>

Hi Chris,
Thanks for the patch, please see comments below.

> ---
> 
>  drivers/gpu/drm/rockchip/cdn-dp-core.c | 20 ++++++++++++++++++++
>  drivers/gpu/drm/rockchip/cdn-dp-reg.c  | 19 +++++++++++++++++++
>  drivers/gpu/drm/rockchip/cdn-dp-reg.h  |  6 ++++++
>  3 files changed, 45 insertions(+)
> 
> diff --git a/drivers/gpu/drm/rockchip/cdn-dp-core.c b/drivers/gpu/drm/rockchip/cdn-dp-core.c
> index 9b0b058..e59ca47 100644
> --- a/drivers/gpu/drm/rockchip/cdn-dp-core.c
> +++ b/drivers/gpu/drm/rockchip/cdn-dp-core.c
> @@ -802,6 +802,7 @@ static int cdn_dp_audio_hw_params(struct device *dev,  void *data,
>  		.sample_rate = params->sample_rate,
>  		.channels = params->channels,
>  	};
> +	u8 buffer[14];

Why 14?

I think you should probably have buffer[HDMI_AUDIO_INFOFRAME_SIZE +
SDP_HEADER_SIZE] so the reader knows how you arrived at this value.

>  	int ret;
>  
>  	mutex_lock(&dp->lock);
> @@ -823,6 +824,25 @@ static int cdn_dp_audio_hw_params(struct device *dev,  void *data,
>  		goto out;
>  	}
>  
> +	memset(buffer, 0, sizeof(buffer));
> +
> +	ret = hdmi_audio_infoframe_pack(&params->cea, buffer, sizeof(buffer));
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "Failed to pack audio infoframe: %d\n", ret);
> +		goto out;
> +	}
> +
> +	/*
> +	 * Change the infoframe header to SDP header per DP 1.3 spec, Table
> +	 * 2-98.
> +	 */
> +	buffer[0] = 0;
> +	buffer[1] = HDMI_INFOFRAME_TYPE_AUDIO;
> +	buffer[2] = 0x1b;
> +	buffer[3] = 0x48;

Instead of doing this, consider splitting up hdmi_audio_infoframe_pack into
hdmi_audio_infoframe_pack and hdmi_audio_infoframe_pack_payload. The first
function does everything, while the second just packs the payload, then you can
set the SDP header independently.

> +
> +	cdn_dp_sdp_write(dp, 0, buffer, sizeof(buffer));
> +
>  	ret = cdn_dp_audio_config(dp, &audio);
>  	if (!ret)
>  		dp->audio_info = audio;
> diff --git a/drivers/gpu/drm/rockchip/cdn-dp-reg.c b/drivers/gpu/drm/rockchip/cdn-dp-reg.c
> index b14d211..8907db0 100644
> --- a/drivers/gpu/drm/rockchip/cdn-dp-reg.c
> +++ b/drivers/gpu/drm/rockchip/cdn-dp-reg.c
> @@ -951,6 +951,25 @@ static void cdn_dp_audio_config_spdif(struct cdn_dp_device *dp)
>  	clk_set_rate(dp->spdif_clk, CDN_DP_SPDIF_CLK);
>  }
>  
> +void cdn_dp_sdp_write(struct cdn_dp_device *dp, int entry_id, u8 *buf, u32 len)
> +{
> +	int idx;
> +	u32 *packet = (u32 *)buf;
> +	u32 length = len / 4;

length and len are pretty terrible names, it would be quite easy to use the
wrong one. Consider more descriptive names (ie: buf_len and num_packets).

> +	u8 type = buf[1];

Check for len < 0?

> +
> +	for (idx = 0; idx < length; idx++)
> +		writel(cpu_to_le32(*packet++), dp->regs + SOURCE_PIF_DATA_WR);
> +
> +	writel(entry_id, dp->regs + SOURCE_PIF_WR_ADDR);
> +
> +	writel(F_HOST_WR, dp->regs + SOURCE_PIF_WR_REQ);
> +
> +	writel(PIF_PKT_TYPE_VALID | F_PACKET_TYPE(type) | entry_id,
> +	       dp->regs + SOURCE_PIF_PKT_ALLOC_REG);
> +	writel(PIF_PKT_ALLOC_WR_EN, dp->regs + SOURCE_PIF_PKT_ALLOC_WR_EN);
> +}
> +
>  int cdn_dp_audio_config(struct cdn_dp_device *dp, struct audio_info *audio)
>  {
>  	int ret;
> diff --git a/drivers/gpu/drm/rockchip/cdn-dp-reg.h b/drivers/gpu/drm/rockchip/cdn-dp-reg.h
> index c4bbb4a83..6ec0e81 100644
> --- a/drivers/gpu/drm/rockchip/cdn-dp-reg.h
> +++ b/drivers/gpu/drm/rockchip/cdn-dp-reg.h
> @@ -424,6 +424,11 @@
>  /* Reference cycles when using lane clock as reference */
>  #define LANE_REF_CYC				0x8000
>  
> +#define F_HOST_WR		BIT(0)
> +#define PIF_PKT_ALLOC_WR_EN	BIT(0)
> +#define PIF_PKT_TYPE_VALID	(3 << 16)
> +#define F_PACKET_TYPE(x)	(((x) & 0xff) << 8)

Can you tuck these #defines under the definition of SOURCE_PIF_PKT_ALLOC_REG, so
we know which register they apply to?

> +
>  enum voltage_swing_level {
>  	VOLTAGE_LEVEL_0,
>  	VOLTAGE_LEVEL_1,
> @@ -478,5 +483,6 @@ int cdn_dp_set_video_status(struct cdn_dp_device *dp, int active);
>  int cdn_dp_config_video(struct cdn_dp_device *dp);
>  int cdn_dp_audio_stop(struct cdn_dp_device *dp, struct audio_info *audio);
>  int cdn_dp_audio_mute(struct cdn_dp_device *dp, bool enable);
> +void cdn_dp_sdp_write(struct cdn_dp_device *dp, int entry_id, u8 *buf, u32 len);
>  int cdn_dp_audio_config(struct cdn_dp_device *dp, struct audio_info *audio);
>  #endif /* _CDN_DP_REG_H */
> -- 
> 2.6.3
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS