[PATCH] riscv: Fix Kendryte K210 device tree

[Anup Patel]

> -----Original Message-----
> From: Sean Anderson <seanga2 at gmail.com>
> Sent: 16 September 2020 07:46
> To: Damien Le Moal <Damien.LeMoal at wdc.com>; linux-
> riscv at lists.infradead.org; Palmer Dabbelt <palmer at dabbelt.com>
> Cc: Anup Patel <Anup.Patel at wdc.com>
> Subject: Re: [PATCH] riscv: Fix Kendryte K210 device tree
> 
> 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:
> 
> 
> 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?

I agree. Only change in interrupts-extended is required and change in reg
property can be dropped.

Regards,
Anup

> 
> > +			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.
> 
> >  		};
> >
> >
> 
> [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 at gmail.com/
> [3]
> https://patchwork.ozlabs.org/project/uboot/patch/20200915141724.503929-
> 9-seanga2 at gmail.com/