[PATCH] riscv: Fix Kendryte K210 device tree

[Sean Anderson]

On 9/15/20 11:08 PM, Damien Le Moal wrote:
> On 2020/09/16 11:15, Sean Anderson wrote:
>> On 9/15/20 8:55 AM, Damien Le Moal wrote:
>>> The Kendryte K210 SoC CLINT is compatible with Sifive clint v0
>>> (sifive,clint0). Fix the Kendryte K210 device tree clint entry to be
>>> inline with the sifive timer definition documented in
>>> Documentation/devicetree/bindings/timer/sifive,clint.yaml. Rename the
>>> clint0 entry to "timer", fix the register mapping and fix the interrupt
>>> extended entry.
>>>
>>> This fixes boot failures with Kendryte K210 SoC boards.
>>>
>>> Signed-off-by: Damien Le Moal <damien.lemoal at wdc.com>
>>> ---
>>>  arch/riscv/boot/dts/kendryte/k210.dtsi | 7 ++++---
>>>  1 file changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/riscv/boot/dts/kendryte/k210.dtsi b/arch/riscv/boot/dts/kendryte/k210.dtsi
>>> index c1df56ccb8d5..48d65fea45e9 100644
>>> --- a/arch/riscv/boot/dts/kendryte/k210.dtsi
>>> +++ b/arch/riscv/boot/dts/kendryte/k210.dtsi
>>> @@ -95,10 +95,11 @@ sysctl: sysctl at 50440000 {
>>>  			#clock-cells = <1>;
>>>  		};
>>>  
>>> -		clint0: interrupt-controller at 2000000 {
>>> +		timer at 2000000 {
>>>  			compatible = "riscv,clint0";
>>> -			reg = <0x2000000 0xC000>;
>>> -			interrupts-extended = <&cpu0_intc 3>,  <&cpu1_intc 3>;
>>> +			reg = <0x2000000 0x10000>;
>>
>> Why the change in size? The docs from the SDK [1] (which I think were copied
>> from SiFive documentation around the time of their release) state that
>> the CLINT is 0xC000 bytes. In addition, accessing memory past 0x0200C000
>> yields a repeating memory pattern:
> 
> Oops. Copy-paste error. I will change that back to 0x0000C000.
>>
>>
>> 0200c000: 69823183 02020120 6083c006 00008002    .1.i ......`....
>> 0200c010: 69823183 02020120 6083c006 00008002    .1.i ......`....
>> 0200c020: 69823183 02020120 6083c006 00008002    .1.i ......`....
>> 0200c030: 69823183 02020120 6083c006 00008002    .1.i ......`....
>> (continues until 0x02010000)
>>
>> To me, it is clear that the CLINT is not 0x10000 in size, even though
>> the legal address space extends to that size.
>>
>> I am more curious how this fixes booting. What was the issue before?
> 
> There were 2 problems:
> 1) The old declaration of the entry as clint0: interrupt-controller at 2000000 led
> to a failure to find the driver.
> 2) The interrupt extended entry was wrong
> 
>>
>>> +			interrupts-extended =  <&cpu0_intc 3 &cpu0_intc 7
>>> +						&cpu1_intc 3 &cpu1_intc 7>;
>>>  			clocks = <&sysctl K210_CLK_ACLK>;
>>
>> This clock is 50 times too fast(!) See [2] and [3] for a fix. I don't
>> know if adding a "virtual" clock is the best solution for Linux. I would
>> like to keep the device trees relatively in-sync, so please let me know
>> if you think there is a better solution.
> 
> Huu... Let me check that. Once booted, using commands such as date or time does
> not give me weird results, well at least, before this patch and clint changes. I
> forgot to check yesterday when I tested (I only boot tested). Will check.
> 
> And yes, I will make effort to keep the DT in sync. Is the Kendryte support
> upstream in U-Boot now ? I have not checked recently.

Yes, it was included with release v2020.07.

--Sean

> 
>>
>>>  		};
>>>  
>>>
>>
>> [1] https://github.com/kendryte/kendryte-standalone-sdk/blob/develop/lib/drivers/include/clint.h
>> [2] https://patchwork.ozlabs.org/project/uboot/patch/20200915141724.503929-8-seanga2@gmail.com/
>> [3] https://patchwork.ozlabs.org/project/uboot/patch/20200915141724.503929-9-seanga2@gmail.com/
>>
> 
>