linux-kernel - Re: [PATCH] media: mediatek: vcodec: support 36bit physical address

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Date: Wed, 6 Mar 2024 08:07:58 +0000
From: Yunfei Dong (董云飞) <Yunfei.Dong@...iatek.com>
To: "sebastian.fricke@...labora.com" <sebastian.fricke@...labora.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"frkoenig@...omium.org" <frkoenig@...omium.org>, "stevecho@...omium.org"
	<stevecho@...omium.org>, "nhebert@...omium.org" <nhebert@...omium.org>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"nicolas.dufresne@...labora.com" <nicolas.dufresne@...labora.com>,
	"daniel@...ll.ch" <daniel@...ll.ch>, Project_Global_Chrome_Upstream_Group
	<Project_Global_Chrome_Upstream_Group@...iatek.com>,
	"benjamin.gaignard@...labora.com" <benjamin.gaignard@...labora.com>,
	"hverkuil-cisco@...all.nl" <hverkuil-cisco@...all.nl>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "hsinyi@...omium.org"
	<hsinyi@...omium.org>, "angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>, "nfraprado@...labora.com"
	<nfraprado@...labora.com>
Subject: Re: [PATCH] media: mediatek: vcodec: support 36bit physical address

Hi Sebastian,

Thanks for your advice.
On Fri, 2024-03-01 at 10:52 +0100, Sebastian Fricke wrote:
> Hey Yunfei,
> 
> On 01.03.2024 10:01, Yunfei Dong wrote:
> > The physical address is beyond 32bit for mt8188 platform, need
> > to change the type from unsigned int to unsigned long in case of
> > the high bit missing.
> 
> I would reword this a bit, the address is not beyond 32 bit, which
> would
> could be interpret as if the address starts after 32nd bit, instead
> it
> is larger than 32bits. Secondly, we don't change the type in case the
> high bit is missing, we change the type unconditionally, we do change
> the type so that the high bit isn't missing.
> 
> My suggestion:
> 
> The physical address on the MT8188 platform is larger than 32 bits,
> change the type from unsigned int to unsigned long to be able to
> access
> the high bits of the address.
> 
I will rewrite the commit message according to your advice.
> One more question below...
> 
> > 
> > Signed-off-by: Yunfei Dong <yunfei.dong@...iatek.com>
> > ---
> > .../mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c        | 4
> > ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git
> > a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_
> > lat_if.c
> > b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_
> > lat_if.c
> > index cf48d09b78d7..85df3e7c2983 100644
> > ---
> > a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_
> > lat_if.c
> > +++
> > b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_
> > lat_if.c
> > @@ -1074,7 +1074,7 @@ static int
> > vdec_vp9_slice_setup_tile_buffer(struct vdec_vp9_slice_instance
> > *inst
> > 	unsigned int mi_row;
> > 	unsigned int mi_col;
> > 	unsigned int offset;
> > -	unsigned int pa;
> > +	unsigned long pa;
> > 	unsigned int size;
> > 	struct vdec_vp9_slice_tiles *tiles;
> > 	unsigned char *pos;
> > @@ -1109,7 +1109,7 @@ static int
> > vdec_vp9_slice_setup_tile_buffer(struct vdec_vp9_slice_instance
> > *inst
> > 	pos = va + offset;
> > 	end = va + bs->size;
> > 	/* truncated */
> > -	pa = (unsigned int)bs->dma_addr + offset;
> > +	pa = (unsigned long)bs->dma_addr + offset;
> 
> I can see in other parts of the driver that bs->dma_addr is converted
> to
> u64 or uint64_t. Is unsigned long always 64-bit on the different
> Mediatek platforms? If so, why do you prefer unsigned long over u64?
> (Which describes the type more precisely)
> 
For 64-bit system, unsigned long is u64 or uint64_t.
The pa is over 32bit for mt8188(64bit system).
The pa is 32bit for mt8195/mt8192/mt8186 etc(64bit system).

pa = (unsigned long)bs->dma_addr + offset;

-> I need to remove 'unsigned long' before bs->dma_addr.
For 32bit pa, the high bit is zero, won't influence the hardware
decoder.

Best Regards,
Yunfei Dong
> (Same applies for:
> drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp8_if.c:452
> )
> 
Ok, I will change it in next patch.
> Greetings,
> Sebastian
> 
> > 	tb = instance->tile.va;
> > 	for (i = 0; i < rows; i++) {
> > 		for (j = 0; j < cols; j++) {
> > -- 
> > 2.18.0
> > 
> >