[PATCH] riscv: Fix Kendryte K210 device tree

[Damien Le Moal]

On Wed, 2020-09-16 at 07:30 -0400, Sean Anderson wrote:
> 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.

Looking at it right now. Trying to fix the clock mess.
I think major surgery of the sysctl code is needed so it will take some
time. The device tree fix v2 I sent still point to the "fake" ACLK
clock for clint MTIME, all wrong. But at run-time, time seems to be OK,
so leaving it as is for now.

Will send a series fixing the clocks & PLL setup, which will allow
enabling more peripherals too :)

Thanks !

> 
> --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/
> > > 

-- 
Damien Le Moal
Western Digital Research