linux-kernel - Re: [RFC PATCH v5 6/6] drm/tidss: Enable Dual and Duplicate Modes for OLDI

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Date:   Wed, 12 Oct 2022 15:35:51 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Aradhya Bhatia <a-bhatia1@...com>, Jyri Sarha <jyri.sarha@....fi>,
        Rob Herring <robh+dt@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
        Rahul T R <r-ravikumar@...com>,
        DRI Development List <dri-devel@...ts.freedesktop.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        Linux Kernel List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v5 6/6] drm/tidss: Enable Dual and Duplicate Modes for
 OLDI

On 28/09/2022 20:52, Aradhya Bhatia wrote:
> The AM625 DSS IP contains 2 OLDI TXes which can work to enable 2
> duplicated displays of smaller resolutions or enable a single Dual Link
> display with a higher resolution (1920x1200).
> 
> Configure the necessary register to enable and disable the OLDI TXes
> with necessary modes configurations.
> 
> Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
> ---
>   drivers/gpu/drm/tidss/tidss_dispc.c | 28 ++++++++++++++++++++++++++--
>   1 file changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c
> index 68444e0cd8d7..fd7f49535f0c 100644
> --- a/drivers/gpu/drm/tidss/tidss_dispc.c
> +++ b/drivers/gpu/drm/tidss/tidss_dispc.c
> @@ -1003,8 +1003,8 @@ static void dispc_enable_oldi(struct dispc_device *dispc, u32 hw_videoport,
>   	int count = 0;
>   
>   	/*
> -	 * For the moment DUALMODESYNC, MASTERSLAVE, MODE, and SRC
> -	 * bits of DISPC_VP_DSS_OLDI_CFG are set statically to 0.
> +	 * For the moment MASTERSLAVE, and SRC bits of DISPC_VP_DSS_OLDI_CFG are
> +	 * set statically to 0.
>   	 */

While at it, maybe say "are always set to 0". At least to me that's much 
more understandable.

>   
>   	if (fmt->data_width == 24)
> @@ -1021,6 +1021,30 @@ static void dispc_enable_oldi(struct dispc_device *dispc, u32 hw_videoport,
>   
>   	oldi_cfg |= BIT(0); /* ENABLE */
>   
> +	switch (dispc->oldi_mode) {
> +	case OLDI_MODE_OFF:
> +		oldi_cfg &= ~BIT(0); /* DISABLE */

Hmm, do we call this if OLDI_MODE_OFF? The current code always enabled 
OLDI here, so I presume we call this only when we actually want to 
enable it.

> +		break;
> +
> +	case OLDI_SINGLE_LINK_SINGLE_MODE:
> +		/* All configuration is done for this mode.  */
> +		break;
> +
> +	case OLDI_SINGLE_LINK_CLONE_MODE:
> +		oldi_cfg |= BIT(5); /* CLONE MODE */
> +		break;
> +
> +	case OLDI_DUAL_LINK_MODE:
> +		oldi_cfg |= BIT(11); /* DUALMODESYNC */
> +		oldi_cfg |= BIT(3); /* data-mapping field also indicates dual-link mode */
> +		break;
> +
> +	default:
> +		dev_warn(dispc->dev, "%s: Incorrect oldi mode. Returning.\n",
> +			 __func__);
> +		return;
> +	}
> +
>   	dispc_vp_write(dispc, hw_videoport, DISPC_VP_DSS_OLDI_CFG, oldi_cfg);
>   
>   	while (!(oldi_reset_bit & dispc_read(dispc, DSS_SYSSTATUS)) &&