linux-kernel - Re: [PATCH 03/23] drm: omapdrm: dss: reset dsi module during initialization

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Date:	Tue, 10 May 2016 15:07:06 +0300
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Sebastian Reichel <sre@...nel.org>,
	Tony Lindgren <tony@...mide.com>,
	Aaro Koskinen <aaro.koskinen@....fi>
CC:	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	David Airlie <airlied@...ux.ie>, <linux-omap@...r.kernel.org>,
	<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/23] drm: omapdrm: dss: reset dsi module during
 initialization



On 08/03/16 18:39, Sebastian Reichel wrote:
> From: Tomi Valkeinen <tomi.valkeinen@...com>
> 
> The Nokia N950's bootloader leaves the DSI module
> in a non-working state. Work around this by resetting
> the DSI module before using it.
> 
> Signed-off-By: Tomi Valkeinen <tomi.valkeinen@...com>
> Reviewed-By: Sebastian Reichel <sre@...nel.org>
> Tested-By: Sebastian Reichel <sre@...nel.org>
> ---
>  drivers/gpu/drm/omapdrm/dss/dsi.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/gpu/drm/omapdrm/dss/dsi.c b/drivers/gpu/drm/omapdrm/dss/dsi.c
> index 43be4b2a7b05..363a61e6aca7 100644
> --- a/drivers/gpu/drm/omapdrm/dss/dsi.c
> +++ b/drivers/gpu/drm/omapdrm/dss/dsi.c
> @@ -5274,6 +5274,28 @@ static int dsi_init_pll_data(struct platform_device *dsidev)
>  	return 0;
>  }
>  
> +static int _dsi_wait_reset(struct platform_device *dsidev)
> +{
> +	int t = 0;
> +
> +	while (REG_GET(dsidev, DSI_SYSSTATUS, 0, 0) == 0) {
> +		 if (++t > 5) {
> +		DSSERR("soft reset failed\n");
> +			return -ENODEV;
> +		 }
> +		 udelay(1);
> +	}
> +
> +	return 0;
> +}
> +
> +static int _dsi_reset(struct platform_device *dsidev)
> +{
> +	/* Soft reset */
> +	dsi_write_reg(dsidev, DSI_SYSCONFIG, 0x2);
> +	return _dsi_wait_reset(dsidev);
> +}
> +
>  /* DSI1 HW IP initialisation */
>  static int dsi_bind(struct device *dev, struct device *master, void *data)
>  {
> @@ -5432,6 +5454,8 @@ static int dsi_bind(struct device *dev, struct device *master, void *data)
>  	if (r)
>  		goto err_runtime_get;
>  
> +	_dsi_reset(dsidev);
> +
>  	rev = dsi_read_reg(dsidev, DSI_REVISION);
>  	dev_dbg(&dsidev->dev, "OMAP DSI rev %d.%d\n",
>  	       FLD_GET(rev, 7, 4), FLD_GET(rev, 3, 0));
> 

This is good as a prototype, but unfortunately we're not supposed to
reset the IP from the driver. I haven't followed if there's a proper
reset framework yet available, but if not, I think we should do the
reset at the platform code at boot time.

Which actually makes me wonder... We should be doing that reset already
there, in mach-omap2/display.c. I wonder why that's not working...

 Tomi



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