linux-kernel - Re: [PATCH v2 01/13] drm/mediatek: add refcount for DPI power on/off

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Date:   Wed, 5 Sep 2018 17:30:35 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Bibby Hsieh <bibby.hsieh@...iatek.com>
CC:     David Airlie <airlied@...ux.ie>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>,
        Yingjoe Chen <yingjoe.chen@...iatek.com>,
        Cawa Cheng <cawa.cheng@...iatek.com>,
        Daniel Kurtz <djkurtz@...omium.org>,
        "Philipp Zabel" <p.zabel@...gutronix.de>,
        YT Shen <yt.shen@...iatek.com>,
        "Thierry Reding" <thierry.reding@...il.com>,
        Mao Huang <littlecvr@...omium.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        "Sascha Hauer" <kernel@...gutronix.de>,
        chunhui dai <chunhui.dai@...iatek.com>
Subject: Re: [PATCH v2 01/13] drm/mediatek: add refcount for DPI power on/off

Hi, Bibby:

This looks reasonable, but why MT8173 doesn't need this patch? So
describe more about why MT7623 need this patch. If this is caused by
latest DRM core flow change, I think we should treat this patch
independent with MT7623.

Regards,
CK

On Wed, 2018-09-05 at 16:31 +0800, Bibby Hsieh wrote:
> From: chunhui dai <chunhui.dai@...iatek.com>
> 
> add refcount for DPI power on/off to protect the flow
> 
> Signed-off-by: chunhui dai <chunhui.dai@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dpi.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dpi.c b/drivers/gpu/drm/mediatek/mtk_dpi.c
> index 6c0ea39d5739..d9373e67d328 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dpi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dpi.c
> @@ -77,6 +77,7 @@ struct mtk_dpi {
>  	enum mtk_dpi_out_bit_num bit_num;
>  	enum mtk_dpi_out_channel_swap channel_swap;
>  	bool power_sta;
> +	int refcount;
>  	u8 power_ctl;
>  };
>  
> @@ -369,6 +370,12 @@ static void mtk_dpi_config_color_format(struct mtk_dpi *dpi,
>  
>  static void mtk_dpi_power_off(struct mtk_dpi *dpi, enum mtk_dpi_power_ctl pctl)
>  {
> +	if (WARN_ON(dpi->refcount == 0))
> +		return;
> +
> +	if (--dpi->refcount != 0)
> +		return;
> +
>  	dpi->power_ctl &= ~pctl;
>  
>  	if ((dpi->power_ctl & DPI_POWER_START) ||
> @@ -388,14 +395,17 @@ static int mtk_dpi_power_on(struct mtk_dpi *dpi, enum mtk_dpi_power_ctl pctl)
>  {
>  	int ret;
>  
> +	if (++dpi->refcount != 1)
> +		return 0;
> +
>  	dpi->power_ctl |= pctl;
>  
>  	if (!(dpi->power_ctl & DPI_POWER_START) &&
>  	    !(dpi->power_ctl & DPI_POWER_ENABLE))
> -		return 0;
> +		goto err_refcount;
>  
>  	if (dpi->power_sta)
> -		return 0;
> +		goto err_refcount;
>  
>  	ret = clk_prepare_enable(dpi->engine_clk);
>  	if (ret) {
> @@ -417,6 +427,8 @@ static int mtk_dpi_power_on(struct mtk_dpi *dpi, enum mtk_dpi_power_ctl pctl)
>  	clk_disable_unprepare(dpi->engine_clk);
>  err_eng:
>  	dpi->power_ctl &= ~pctl;
> +err_refcount:
> +	dpi->refcount--;
>  	return ret;
>  }
>