linux-kernel - Re: [PATCH] drm/rockchip: vop: do axi reset in vop initial time

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Date:	Wed, 1 Jun 2016 17:19:57 +0200
From:	Thierry Reding <treding@...dia.com>
To:	Yakir Yang <ykk@...k-chips.com>
CC:	Mark Yao <yzq@...k-chips.com>, Heiko Stuebner <heiko@...ech.de>,
	<tfiga@...omium.org>, David Airlie <airlied@...ux.ie>,
	<daniel.vetter@...ll.ch>, <dianders@...omium.org>,
	<linux-kernel@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
	<linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH] drm/rockchip: vop: do axi reset in vop initial time

On Wed, Jun 01, 2016 at 05:19:12PM +0800, Yakir Yang wrote:
> There is a bug in RK3399 VOP, when bootloader/kernel only enable
> VOP Big or VOP Little to display, then VOP IOMMU would failed to
> reset at the initial time and VOP register couldn't write rightly.
> 
> After do the pure reset of VOP module, then things back to right.
> 
> Signed-off-by: Yakir Yang <ykk@...k-chips.com>
> ---
>  drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index 1c4d5b5..4150323 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -1292,7 +1292,7 @@ static int vop_initial(struct vop *vop)
>  {
>  	const struct vop_data *vop_data = vop->data;
>  	const struct vop_reg_data *init_table = vop_data->init_table;
> -	struct reset_control *ahb_rst;
> +	struct reset_control *ahb_rst, *axi_rst;
>  	int i, ret;
>  
>  	vop->hclk = devm_clk_get(vop->dev, "hclk_vop");
> @@ -1331,6 +1331,19 @@ static int vop_initial(struct vop *vop)
>  	}
>  
>  	/*
> +	 * do aclk_reset, reset all vop registers.
> +	 */
> +	axi_rst = devm_reset_control_get(vop->dev, "axi");

I don't think you want the managed version here since you only store
this in a local variable and hence aren't going to need it afterwards.
Just use reset_control_get() and ...

> +	if (IS_ERR(axi_rst)) {
> +		dev_err(vop->dev, "failed to get axi reset\n");
> +		ret = PTR_ERR(axi_rst);
> +		goto err_disable_aclk;
> +	}
> +	reset_control_assert(axi_rst);
> +	usleep_range(10, 20);
> +	reset_control_deassert(axi_rst);

call reset_control_put() here.

> +
> +	/*
>  	 * do hclk_reset, reset all vop registers.
>  	 */
>  	ahb_rst = devm_reset_control_get(vop->dev, "ahb");

This uses the same pattern, so you might want to consider reworking this
as well, though it should be a separate patch.

Thierry

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