linux-kernel - Re: [PATCH v15 1/3] drm: rockchip: Add basic drm driver

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Message-ID: <CAAObsKANPWAHdoFG3SHK_RAwzZ6d=TVKGZP8ukk3a6CxewOajw@mail.gmail.com>
Date:	Mon, 14 Mar 2016 14:35:22 +0100
From:	Tomeu Vizoso <tomeu@...euvizoso.net>
To:	Mark Yao <mark.yao@...k-chips.com>
Cc:	Heiko Stübner <heiko@...ech.de>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	David Airlie <airlied@...il.com>,
	Rob Clark <robdclark@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Grant Likely <grant.likely@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Rom Lemarchand <romlem@...gle.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Douglas Anderson <dianders@...omium.org>,
	Stéphane Marchesin <marcheu@...omium.org>,
	dbehr@...omium.org, Olof Johansson <olof@...om.net>,
	Daniel Kurtz <djkurtz@...omium.org>,
	Eddie Cai <cf@...k-chips.com>, xxm@...k-chips.com,
	Tao Huang <huangtao@...k-chips.com>,
	Kever Yang <kever.yang@...k-chips.com>, yxj@...k-chips.com,
	xw@...k-chips.com
Subject: Re: [PATCH v15 1/3] drm: rockchip: Add basic drm driver

On 2 December 2014 at 10:15, Mark Yao <mark.yao@...k-chips.com> wrote:
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> new file mode 100644
> index 0000000..e7ca25b
> --- /dev/null
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -0,0 +1,1455 @@
...
> +static bool vop_crtc_mode_fixup(struct drm_crtc *crtc,
> +                               const struct drm_display_mode *mode,
> +                               struct drm_display_mode *adjusted_mode)
> +{
> +       if (adjusted_mode->htotal == 0 || adjusted_mode->vtotal == 0)
> +               return false;

Hi Mark,

what's the rationale for this?

Disabling a CRTC as in [0] will cause mode_fixup() to be called with
an empty mode, failing that test.

Removing the check seems to get things working fine for a short while,
but a later modeset invariably gets the VOP to hang (as reported by
[1]).

Do you know why that check was put in place and what exactly could be
causing the hw to hang?

[0] https://cgit.freedesktop.org/xorg/app/intel-gpu-tools/tree/lib/igt_kms.c#n1616
[1] https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/drivers/gpu/drm/rockchip/rockchip_drm_vop.c#n873

Thanks,

Tomeu

> +
> +       return true;
> +}