linux-kernel - RE: [PATCH] drm/fbdev-dma: fix getting smem

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Message-ID:
 <AM6PR04MB5941216A69AE325A79689C5888C72@AM6PR04MB5941.eurprd04.prod.outlook.com>
Date: Tue, 11 Jun 2024 08:23:09 +0000
From: Peng Fan <peng.fan@....com>
To: Thomas Zimmermann <tzimmermann@...e.de>, "Peng Fan (OSS)"
	<peng.fan@....nxp.com>, Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, Javier
 Martinez Canillas <javierm@...hat.com>
CC: "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] drm/fbdev-dma: fix getting smem_start

> Subject: Re: [PATCH] drm/fbdev-dma: fix getting smem_start
> 
> Hi
> 
> Am 11.06.24 um 03:00 schrieb Peng Fan:
> >> Subject: Re: [PATCH] drm/fbdev-dma: fix getting smem_start
> >>
> >> Hi
> >>
> >> Am 04.06.24 um 10:03 schrieb Peng Fan (OSS):
> >>> From: Peng Fan <peng.fan@....com>
> >>>
> >>> If 'info->screen_buffer' locates in vmalloc address space,
> >>> virt_to_page will not be able to get correct results. With
> >>> CONFIG_DEBUG_VM and CONFIG_DEBUG_VIRTUAL enabled on ARM64,
> >> there is dump below:
> >>
> >> Which graphics driver triggers this bug?
> > It is NXP i.MX95 DPU driver which is still in NXP downstream repo.
> 
> Which DRM memory manager does that driver use?

DRM_GEM_DMA_DRIVER_OPS

> 
> I'm asking because if the driver allocates BOs via vmalloc(), should it really
> use fbdev-dma?

We use it for fbdev emulation. If drm_kms_helper.fbdev_emulation is 0,
fbdev emulation could be disabled.

Thanks
Peng
> 
> Best regards
> Thomas
> 
> >
> > Thanks,
> > Peng.
> 
> --
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Frankenstrasse 146, 90461 Nuernberg, Germany
> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB
> 36809 (AG Nuernberg)