Hello Marek,

On 05/27/2016 07:32 AM, Marek Szyprowski wrote:

Hello,


On 2016-05-25 19:11, Javier Martinez Canillas wrote:

quoted

Hello Marek,

On 05/24/2016 09:31 AM, Marek Szyprowski wrote:

quoted

This patch replaces custom properties for defining reserved memory
regions with generic reserved memory bindings for MFC video codec
device.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---

[snip]

quoted

+
+/ {
+    reserved-memory {
+        #address-cells = <1>;
+        #size-cells = <1>;
+        ranges;
+
+        mfc_left: region@51000000 {
+            compatible = "shared-dma-pool";
+            no-map;
+            reg = <0x51000000 0x800000>;
+        };
+
+        mfc_right: region@43000000 {
+            compatible = "shared-dma-pool";
+            no-map;
+            reg = <0x43000000 0x800000>;
+        };
+    };

I've a question probably for a follow up patch, but do you know what's a
sane default size for these? I needed to bump the mfc_left size from 8 MiB
to 16 MiB in order to decode a 480p H264 video using GStramer. So clearly
the default sizes are not that useful.

Right, the default size for the 'left' region can be increased. Frankly, those
values (8MiB/0x43000000+ 8MiB/0x51000000) comes from my initial patches
prepared for some demo and don't have much with any real requirements. They
were copied (blindly...) by various developers without any deeper understanding.

Yes, I've to admit that I was one of those when added the MFC regions to the
Peach Chromebooks but worked because I tested with small videos. When trying
to decode bigger videos, then had to increase the 'left' region as mentioned.

Probably the most sane would be to use something like this:

mfc_left: region_mfc_left {
         compatible = "shared-dma-pool";
         no-map;
         size = <0x1000000>;
         alignment = <0x100000>;
};

mfc_right: region_mfc_right {
         compatible = "shared-dma-pool";
         no-map;
         size = <0x800000>;
         alignment = <0x100000>;
};

So the region will be allocated automatically from the available memory. This way
another nice feature of the generic reserved memory regions can be used.

That sounds better indeed. Not requiring a certain memory offset will also have the
nice side effect to prevent conflicts like the one Pankaj had with his initramfs [0].
 

The only platform which really requires MFC regions to be placed at certain memory
offsets is Samsung S5PV210/S5PC110 (sometimes called exynos3), where there is no
memory address interleaving and MFC device has limited memory interface, which cannot
do 2 transactions to the same physical memory bank. However S5PV210/S5PC110 machine
code lost support for MFC during conversion to device tree, so it is not a problem
here.

All newer platforms (Exynos4, Exynos3250, Exynos5+) use memory interleaving, so the
actual offset of memory bank has no influence on the physical memory bank.

I see, thanks a lot for the explanation.
 

quoted

quoted

+};

diff --git a/arch/arm/boot/dts/exynos4210-origen.dts b/arch/arm/boot/dts/exynos4210-origen.dts
index ad7394c..f5e4eb2 100644
--- a/arch/arm/boot/dts/exynos4210-origen.dts
+++ b/arch/arm/boot/dts/exynos4210-origen.dts

@@ -18,6 +18,7 @@
  #include "exynos4210.dtsi"
  #include <dt-bindings/gpio/gpio.h>
  #include <dt-bindings/input/input.h>
+#include "exynos-mfc-reserved-memory.dtsi"
    / {
      model = "Insignal Origen evaluation board based on Exynos4210";

@@ -288,8 +289,7 @@
  };
    &mfc {
-    samsung,mfc-r = <0x43000000 0x800000>;
-    samsung,mfc-l = <0x51000000 0x800000>;
+    memory-region = <&mfc_left>, <&mfc_right>;
      status = "okay";

I wonder if shouldn't be better to include the exynos-mfc-reserved-memory.dtsi
on each SoC dtsi and set the memory-regions in the MFC node instead of doing
it on each DTS, and let DTS to just replace with its own memory regions if the
default sizes are not suitable for them.

I don't have strong opinion on this. Maybe it would make more sense to move the
following entry:

&mfc {
        memory-region = <&mfc_left>, <&mfc_right>;
};

also to the exynos-mfc-reserved-memory.dtsi ? So board will just include it if
it want to use MFC device with reserved memory regions.

Ok, that also sounds like a good option for me.
 

quoted

Reviewed-by: Javier Martinez Canillas <redacted>
Tested-by: Javier Martinez Canillas <redacted>

Best regards

[0]: https://lkml.org/lkml/2016/5/26/98

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America