Messages in this thread | | | From | Alexey Brodkin <> | Subject | Re: [PATCH 2/2] ARC: [axs10x] Specify reserved memory for frame buffer | Date | Thu, 28 Apr 2016 13:46:22 +0000 |
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Hi Vineet,
On Thu, 2016-04-28 at 09:56 +0530, Vineet Gupta wrote:
[snip]
> > > > diff --git a/arch/arc/boot/dts/axc001.dtsi b/arch/arc/boot/dts/axc001.dtsi > > index 420dcfd..ae6162d 100644 > > --- a/arch/arc/boot/dts/axc001.dtsi > > +++ b/arch/arc/boot/dts/axc001.dtsi > > @@ -95,6 +95,24 @@ > > #size-cells = <1>; > > ranges = <0x00000000 0x80000000 0x40000000>; > > device_type = "memory"; > > - reg = <0x80000000 0x20000000>; /* 512MiB */ > > + reg = <0x80000000 0x1f000000>; /* 512 - 16 MiB */ > Is 16MB fixed size or is this a function of display resolution / density etc.
Indeed this value depends on screen resolution and bpp and double- or even tripple-buffering (once this becomes supported in the driver).
So as of now the corner case would be 1920x1080, 16 bits per pixel which gives ~4Mb. Now if we add support of triple-buffering we'll need ~12Mb so I booked a little bit more - 16Mb.
But now I recalled that we also support r8g8b8 mode and in this case 3 bytes are used for color encoding, which effectively gives ~6Mb for 1 FullHD frame. And for tripple-buffering we'll need > 18Mb, so probably we'll need to go for 24 or even 32 Mb.
[snip]
> > + > > + reserved-memory { > > + #address-cells = <1>; > > + #size-cells = <1>; > > + ranges; > > + /* > > + * Move frame buffer out of IOC aperture (0x8z-0xAz). > > + */ > > + frame_buffer: frame_buffer@bf000000 { > > + compatible = "shared-dma-pool"; > > + reg = <0xbf000000 0x1000000>; > Can this be made a bit more future safe. AXS103 has 1 GB of DDR while kernel > currently only uses 512M. Once we increase that, this will need fixing too. Better > to make this as far possible.
Makes sense. Will move it to the very end of 1Gb.
> Note that the IOC start alignment needs to follow > max(4k, size). What will be maximum size of frame buffer - 16M always !
What do you mean by that?
-Alexey
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