linux-kernel - Re: [PATCH v2 2/2] drm/bridge: ti-sn65dsi83: Fix enable/disable flow to meet spec

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Message-ID: <2225400.iZASKD2KPV@steina-w>
Date:   Thu, 04 May 2023 11:11:14 +0200
From:   Alexander Stein <alexander.stein@...tq-group.com>
To:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>
Cc:     Marek Vasut <marex@...x.de>, Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Sam Ravnborg <sam@...nborg.org>,
        Frieder Schrempf <frieder@...s.de>
Subject: Re: [PATCH v2 2/2] drm/bridge: ti-sn65dsi83: Fix enable/disable flow to meet spec

Am Mittwoch, 3. Mai 2023, 18:33:07 CEST schrieb Frieder Schrempf:
> From: Frieder Schrempf <frieder.schrempf@...tron.de>
> 
> The datasheet describes the following initialization flow including
> minimum delay times between each step:
> 
> 1. DSI data lanes need to be in LP-11 and the clock lane in HS mode
> 2. toggle EN signal
> 3. initialize registers
> 4. enable PLL
> 5. soft reset
> 6. enable DSI stream
> 7. check error status register
> 
> To meet this requirement we need to make sure the host bridge's
> pre_enable() is called first by using the pre_enable_prev_first
> flag.
> 
> Furthermore we need to split enable() into pre_enable() which covers
> steps 2-5 from above and enable() which covers step 7 and is called
> after the host bridge's enable().
> 
> Signed-off-by: Frieder Schrempf <frieder.schrempf@...tron.de>

Tested-by: Alexander Stein <alexander.stein@...tq-group.com> #TQMa8MxML/MBa8Mx

> ---
> Changes for v2:
> * Drop RFC
> ---
>  drivers/gpu/drm/bridge/ti-sn65dsi83.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> b/drivers/gpu/drm/bridge/ti-sn65dsi83.c index 75286c9afbb9..a82f10b8109f
> 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> @@ -321,8 +321,8 @@ static u8 sn65dsi83_get_dsi_div(struct sn65dsi83 *ctx)
>  	return dsi_div - 1;
>  }
> 
> -static void sn65dsi83_atomic_enable(struct drm_bridge *bridge,
> -				    struct drm_bridge_state 
*old_bridge_state)
> +static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge,
> +					struct drm_bridge_state 
*old_bridge_state)
>  {
>  	struct sn65dsi83 *ctx = bridge_to_sn65dsi83(bridge);
>  	struct drm_atomic_state *state = old_bridge_state->base.state;
> @@ -484,11 +484,22 @@ static void sn65dsi83_atomic_enable(struct drm_bridge
> *bridge, /* Trigger reset after CSR register update. */
>  	regmap_write(ctx->regmap, REG_RC_RESET, REG_RC_RESET_SOFT_RESET);
> 
> +	/* Wait for 10ms after soft reset as specified in datasheet */
> +	usleep_range(10000, 12000);
> +}
> +
> +static void sn65dsi83_atomic_enable(struct drm_bridge *bridge,
> +				    struct drm_bridge_state 
*old_bridge_state)
> +{
> +	struct sn65dsi83 *ctx = bridge_to_sn65dsi83(bridge);
> +	unsigned int pval;
> +
>  	/* Clear all errors that got asserted during initialization. */
>  	regmap_read(ctx->regmap, REG_IRQ_STAT, &pval);
>  	regmap_write(ctx->regmap, REG_IRQ_STAT, pval);
> 
> -	usleep_range(10000, 12000);
> +	/* Wait for 1ms and check for errors in status register */
> +	usleep_range(1000, 1100);
>  	regmap_read(ctx->regmap, REG_IRQ_STAT, &pval);
>  	if (pval)
>  		dev_err(ctx->dev, "Unexpected link status 0x%02x\n", 
pval);
> @@ -555,6 +566,7 @@ static const struct drm_bridge_funcs sn65dsi83_funcs = {
> .attach			= sn65dsi83_attach,
>  	.detach			= sn65dsi83_detach,
>  	.atomic_enable		= sn65dsi83_atomic_enable,
> +	.atomic_pre_enable	= sn65dsi83_atomic_pre_enable,
>  	.atomic_disable		= sn65dsi83_atomic_disable,
>  	.mode_valid		= sn65dsi83_mode_valid,
> 
> @@ -697,6 +709,7 @@ static int sn65dsi83_probe(struct i2c_client *client)
> 
>  	ctx->bridge.funcs = &sn65dsi83_funcs;
>  	ctx->bridge.of_node = dev->of_node;
> +	ctx->bridge.pre_enable_prev_first = true;
>  	drm_bridge_add(&ctx->bridge);
> 
>  	ret = sn65dsi83_host_attach(ctx);


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