Re: ARM GIC DT binding reg block mismatch? (Re: [PATCH v11 1/8] arm64: renesas: r8a7795: Add Renesas R8A7795 SoC support)

On 15/02/16 18:53, Dirk Behme wrote:

On 15.02.2016 11:55, Marc Zyngier wrote:

quoted

On 15/02/16 10:35, Geert Uytterhoeven wrote:

quoted

Hi Marc,

On Mon, Feb 15, 2016 at 9:45 AM, Marc Zyngier [off-list ref] wrote:

quoted

On 15/02/16 08:16, Geert Uytterhoeven wrote:

quoted

On Wed, Dec 9, 2015 at 9:23 AM, Geert Uytterhoeven [off-list ref] wrote:

quoted

On Tue, Nov 3, 2015 at 3:28 PM, Mark Rutland [off-list ref] wrote:

quoted

On Wed, Oct 21, 2015 at 03:34:39PM +0200, Geert Uytterhoeven wrote:

quoted

On Thu, Oct 15, 2015 at 12:58 PM, Mark Rutland [off-list ref] wrote:

quoted

quoted

quoted

+           gic: interrupt-controller@0xf1010000 {

+                     compatible = "arm,gic-400";
+                     #interrupt-cells = <3>;
+                     #address-cells = <0>;
+                     interrupt-controller;
+                     reg = <0x0 0xf1010000 0 0x1000>,
+                           <0x0 0xf1020000 0 0x2000>;
+                     interrupts = <GIC_PPI 9
+                                     (GIC_CPU_MASK_SIMPLE(1) | IRQ_TYPE_LEVEL_HIGH)>;
+             };

No GICH and GICV?

These seem to be defined in the "arm,gic-v3" DT bindings only, while this is
an "arm,gic-400" (GICD_IIDR 0x0200043b)?

See the "GIC virtualization extensions (VGIC)" section in
Documentation/devicetree/bindings/arm/gic.txt

DDI0471B_gic400_r0p1_trm.pdf says:

     Address range GIC-400 functional block
     A. 0x0000 - 0x0FFF Reserved
     B. 0x1000 - 0x1FFF Distributor
     C. 0x2000 - 0x3FFF CPU interfaces
     D. 0x4000 - 0x4FFF Virtual interface control block, for the processor that
                        is performing the access
     E. 0x5000 - 0x5FFF Virtual interface control block, for the processor
                        selected by address bits [11:9]
     F. 0x6000 - 0x7FFF Virtual CPU interfaces

The DT binding document says:
   1. The  first region is the GIC distributor register base and size.
   2. The 2nd region is the GIC cpu interface register base and size.
   3. The first additional region is the GIC virtual interface control register
      base and size.
   4. The 2nd additional region is the GIC virtual cpu interface register base
      and size.

Matching with the example:

         interrupt-controller@2c001000 {
                 compatible = "arm,cortex-a15-gic";
                 #interrupt-cells = <3>;
                 interrupt-controller;
                 reg = <0x2c001000 0x1000>,
                       <0x2c002000 0x1000>,
                       <0x2c004000 0x2000>,
                       <0x2c006000 0x2000>;
                 interrupts = <1 9 0xf04>;
         };

This means:
   - reg entry 1. covers address range B,
   - reg entry 2. covers address range C,
   - reg entry 3. covers address ranges D _and_ E,
   - reg entry 4. covers address range F.

On R-Car Gen3, the base addresses are:

     Distributor             : 0xF101_0000
     CPU interfaces          : 0xF102_0000
     Virtual interfaces      : 0xF104_0000
     Virtual interfaces      : 0xF105_0000
     Virtual CPU interfaces  : 0xF106_0000

Note the additional multiplication factor of 16 in the offsets relative to
the base address 0xf1000000 (e.g. 0x50000 instead of 0x5000).

As address ranges D and E are merged in a single reg entry, how is the GIC
driver supposed to know about this multiplication factor?

The answer is very simple, the GIC driver doesn't give a damn about the
second part of the GICH region, because it is absolutely unusable for
any realistic use-case. Only the banked version of GICH is of any
relevance (the first 512 bytes, in essence).

Aligning the GIC regions on 64kB boundaries is documented in the SBSA
specification, independently of the GIC400 documentation.

If I understand the SBSA spec correctly (BTW, arm,gic.txt doesn't use the
"GICC" terminology, unlike arm,gic-v3.txt), that means reg entry 3 should be
"<0xf104f000 0x2000>", so it covers the aliased last 4 KiB of address range D,
and the first 4 KiB of address range E. I.e.

                         reg = <0x0 0xf1010000 0 0x1000>,
                              <0x0 0xf1020000 0 0x2000>,
                              <0x0 0xf104f000 0 0x2000>,
                              <0x0 0xf1060000 0 0x2000>;

Is that correct?

My preference would be to expose the full 128kB of the region

That would be

<0x0 0xf1040000 0 0x20000>

then? Ok?

Exactly.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
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