Re: [PATCH v3 3/6] ARM: dts: sun8i: v3s: Add node for system control

From: Samuel Holland
Date: Sat Dec 05 2020 - 13:45:53 EST

Next message: Jonathan Cameron: "Re: [PATCH 1/3] iio: dummy: convert all simple allocation devm_ variants"
Previous message: Jarod Wilson: "Re: [PATCH net v3] bonding: fix feature flag setting at init time"
In reply to: Chen-Yu Tsai: "Re: [PATCH v3 3/6] ARM: dts: sun8i: v3s: Add node for system control"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

On 12/3/20 10:44 AM, Chen-Yu Tsai wrote:
> On Fri, Dec 4, 2020 at 12:25 AM Martin Cerveny <martin@xxxxxxxxx> wrote:
>>
>> Hello.
>>
>> On Thu, 3 Dec 2020, Chen-Yu Tsai wrote:
>>
>>> Hi,
>>>
>>> On Mon, Nov 16, 2020 at 8:57 PM Martin Cerveny <m.cerveny@xxxxxxxxxxxx> wrote:
>>>>
>>>> Allwinner V3s has system control and SRAM C1 region similar to H3.
>>>>
>>>> Signed-off-by: Martin Cerveny <m.cerveny@xxxxxxxxxxxx>
>>>> ---
>>>> arch/arm/boot/dts/sun8i-v3s.dtsi | 14 ++++++++++++++
>>>> 1 file changed, 14 insertions(+)
>>>>
>>>> diff --git a/arch/arm/boot/dts/sun8i-v3s.dtsi b/arch/arm/boot/dts/sun8i-v3s.dtsi
>>>> index 0c7341676921..70193512c222 100644
>>>> --- a/arch/arm/boot/dts/sun8i-v3s.dtsi
>>>> +++ b/arch/arm/boot/dts/sun8i-v3s.dtsi
>>>> @@ -161,6 +161,20 @@ syscon: system-control@1c00000 {
>>>> #address-cells = <1>;
>>>> #size-cells = <1>;
>>>> ranges;
>>>> +
>>>> + sram_c: sram@1d00000 {
>>>> + compatible = "mmio-sram";
>>>> + reg = <0x01d00000 0x80000>;
>>>
>>> How was this address derived? Did you check that there is actually SRAM here?
>>
>> Yes, I did some checking (mmap). But I repeated measurement and found
>> mirrored regions:
>>
>> - SRAM_C is mirrored from 0x0000_4000 (primary location) to 0x01d0_4000 (size 0xb000)
>> (probably exact size is 0xb0c0)
>> - rest of 0x01d0_0000 are discontinuously filled with R/W register sets
>> (probably some internals registers from VE) that I thought to be SRAM too
>> - register SRAM_CTRL_REG0==0x01c00_0000 (value 0x7fff_ffff) switch whole
>> region 0x01d0_0000-0x01df_ffff __AND__ 0x0000_4000-0x0000_ffff
>> - VE/cedrus code use this regions indirectly
>> (VE_AVC_SRAM_PORT_OFFSET/VE_AVC_SRAM_PORT_DATA...)
>> and it is not influenced by "true" SRAM mapping or size
>
> Could you add this to your commit log? That would make the information
> available to others, and you could mention that you only added the
> location that is contiguous SRAM without the interspersed registers.
>
> So based on this, and what we've seen with the H616, I'm guessing
> 0x01d0_0000 - 0x01df_ffff exposes all the internal guts of the VE,
> while SRAM C @ 0x4000 just maps a small portion out.
>
>> -> so I suppose to better use only SRAM_C lower definition:
>
> Yes that would be more appropriate, as it matches the manual, and as you
> mentioned, is *real* SRAM.

My reading of the manual and comments in the BSP U-Boot is that the high
address near the VE registers is the "real" address. The alternate SRAM
mapping just past the end of SRAM A1 exists specifically so the boot ROM
can load boot0/TOC0 images larger than would fit in SRAM A1.

I don't have a copy of the V3s BROM, but here's the logic from the
beginning of the H6 SBROM, which first enables the VE bus clock and
reset before mapping the SRAM:

; VE_BGR_REG |= BIT(16)
2dc: e59f113c ldr r1, [pc, #316] ; 420
2e0: e5912000 ldr r2, [r1]
2e4: e3a03801 mov r3, #65536 ; 0x10000
2e8: e1822003 orr r2, r2, r3
2ec: e5812000 str r2, [r1]
; VE_BGR_REG |= BIT(0)
2f0: e59f1128 ldr r1, [pc, #296] ; 420
2f4: e5912000 ldr r2, [r1]
2f8: e3a03001 mov r3, #1
2fc: e1822003 orr r2, r2, r3
300: e5812000 str r2, [r1]
; SRAM_CTRL_REG0 &= BIT(31)
304: e3a01403 mov r1, #50331648 ; 0x3000000
308: e5912000 ldr r2, [r1]
30c: e3c220ff bic r2, r2, #255 ; 0xff
310: e3c22cff bic r2, r2, #65280 ; 0xff00
314: e3c228ff bic r2, r2, #16711680 ; 0xff0000
318: e3c2247f bic r2, r2, #2130706432 ; 0x7f000000
31c: e5812000 str r2, [r1]
; SRAM_CTRL_REG1 = BIT(24) | BIT(0)
320: e59f10fc ldr r1, [pc, #252] ; 424
324: e3a02401 mov r2, #16777216 ; 0x1000000
328: e1822003 orr r2, r2, r3
32c: e5812000 str r2, [r1]
...
420: .word 0300169c
424: .word 03000004

Then U-Boot SPL[1] sets the SRAM back to "normal mode" before turning
off the VE gating and reset:

//VE SRAM:set sram to normal mode, default boot mode
reg_val = readl(SUNXI_SYSCRL_BASE+0X0004);
reg_val &= ~(0x1<<24);
writel(reg_val, SUNXI_SYSCRL_BASE+0X0004);

//VE gating&VE Bus Reset :brom set them, but not require now
reg_val = readl(CCMU_VE_BGR_REG);
reg_val &= ~(0x1<<0);
reg_val &= ~(0x1<<16);
writel(reg_val, CCMU_VE_BGR_REG);

Other SoCs have a similar code to unmap SRAM C[2]. The AHB1 bus clock
frequency limitation makes sense given that it has to go through the VE
hardware block to get to the SRAM.

In fact, the AHB1 clock limitation when using the low mapping should be
reason enough to prefer the high mapping.

Cheers,
Samuel

[1]:
https://github.com/Allwinner-Homlet/H6-BSP4.9-brandy/blob/master/u-boot-2014.07/board/sunxi/sun50iw6p1/sun50iw6p1.c#L60
[2]:
https://github.com/Allwinner-Homlet/H6-BSP4.9-brandy/blob/master/u-boot-2014.07/board/sunxi/sun8iw10p1/sun8iw10p1.c#L75

>> ---
>> diff --git a/arch/arm/boot/dts/sun8i-v3s.dtsi b/arch/arm/boot/dts/sun8i-v3s.dtsi
>> index e8f304125e2d..90d703e5b73b 100644
>> --- a/arch/arm/boot/dts/sun8i-v3s.dtsi
>> +++ b/arch/arm/boot/dts/sun8i-v3s.dtsi
>> @@ -162,17 +162,17 @@ syscon: system-control@1c00000 {
>> #size-cells = <1>;
>> ranges;
>>
>> - sram_c: sram@1d00000 {
>> + sram_c: sram@4000 {
>> compatible = "mmio-sram";
>> - reg = <0x01d00000 0x80000>;
>> + reg = <0x4000 0xb000>;
>> #address-cells = <1>;
>> #size-cells = <1>;
>> - ranges = <0 0x01d00000 0x80000>;
>> + ranges = <0 0 0x4000 0xb000>;
>>
>> ve_sram: sram-section@0 {
>> compatible = "allwinner,sun8i-v3s-sram-c1",
>> "allwinner,sun4i-a10-sram-c1";
>> - reg = <0x000000 0x80000>;
>> + reg = <0x0 0xb000>;
>> };
>> };
>> };
>> ---
>>
>> Does someone have accessible specific documentation of VE/cedrus for V3s ?
>
> I doubt such information exists.
>
>
> Regards
> ChenYu
>
>> Regards, Martin
>>
>>> ChenYu
>>>
>>>> + #address-cells = <1>;
>>>> + #size-cells = <1>;
>>>> + ranges = <0 0x01d00000 0x80000>;
>>>> +
>>>> + ve_sram: sram-section@0 {
>>>> + compatible = "allwinner,sun8i-v3s-sram-c1",
>>>> + "allwinner,sun4i-a10-sram-c1";
>>>> + reg = <0x000000 0x80000>;
>>>> + };
>>>> + };
>>>> };
>>>>
>>>> tcon0: lcd-controller@1c0c000 {
>>>> --
>>>> 2.25.1
>>>>
>>>>
>>>> _______________________________________________
>>>> linux-arm-kernel mailing list
>>>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>

Next message: Jonathan Cameron: "Re: [PATCH 1/3] iio: dummy: convert all simple allocation devm_ variants"
Previous message: Jarod Wilson: "Re: [PATCH net v3] bonding: fix feature flag setting at init time"
In reply to: Chen-Yu Tsai: "Re: [PATCH v3 3/6] ARM: dts: sun8i: v3s: Add node for system control"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]