The AST2500 SoC family changes the runtime behaviour of the hardware
strapping register (SCU70) to write-1-set/write-1-clear, with
write-1-clear implemented on the "read-only" SoC revision register
(SCU7C). For the the AST2400, the hardware strapping is
runtime-configured with read-modify-write semantics.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
---
 hw/misc/aspeed_scu.c         | 19 +++++++++++++++++--
 include/hw/misc/aspeed_scu.h |  2 ++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/hw/misc/aspeed_scu.c b/hw/misc/aspeed_scu.c
index 5e6d5744eeca..9051767cbbcd 100644
--- a/hw/misc/aspeed_scu.c
+++ b/hw/misc/aspeed_scu.c
@@ -202,11 +202,26 @@ static void aspeed_scu_write(void *opaque, hwaddr offset, uint64_t data,
     case PROT_KEY:
         s->regs[reg] = (data == ASPEED_SCU_PROT_KEY) ? 1 : 0;
         return;
-
+    case HW_STRAP1:
+        if (ASPEED_IS_AST2500(s->regs[SILICON_REV])) {
+            s->regs[HW_STRAP1] |= data;
+            return;
+        }
+        /* Jump to assignment below */
+        break;
+    case SILICON_REV:
+        if (ASPEED_IS_AST2500(s->regs[SILICON_REV])) {
+            s->regs[HW_STRAP1] &= ~data;
+        } else {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "%s: Write to read-only offset 0x%" HWADDR_PRIx "\n",
+                          __func__, offset);
+        }
+        /* Avoid assignment below, we've handled everything */
+        return;
     case FREQ_CNTR_EVAL:
     case VGA_SCRATCH1 ... VGA_SCRATCH8:
     case RNG_DATA:
-    case SILICON_REV:
     case FREE_CNTR4:
     case FREE_CNTR4_EXT:
         qemu_log_mask(LOG_GUEST_ERROR,
diff --git a/include/hw/misc/aspeed_scu.h b/include/hw/misc/aspeed_scu.h
index d70cc0aeca61..169611a211bb 100644
--- a/include/hw/misc/aspeed_scu.h
+++ b/include/hw/misc/aspeed_scu.h
@@ -37,6 +37,8 @@ typedef struct AspeedSCUState {
 #define AST2500_A0_SILICON_REV   0x04000303U
 #define AST2500_A1_SILICON_REV   0x04010303U
 
+#define ASPEED_IS_AST2500(si_rev)     ((((si_rev) >> 24) & 0xff) == 0x04)
+
 extern bool is_supported_silicon_rev(uint32_t silicon_rev);
 
 #define ASPEED_SCU_PROT_KEY      0x1688A8A8
-- 
2.17.1

On 10 July 2018 at 00:35, Andrew Jeffery <andrew@aj.id.au> wrote:
> The AST2500 SoC family changes the runtime behaviour of the hardware
> strapping register (SCU70) to write-1-set/write-1-clear, with
> write-1-clear implemented on the "read-only" SoC revision register
> (SCU7C). For the the AST2400, the hardware strapping is
> runtime-configured with read-modify-write semantics.
>
> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>

Reviewed-by: Joel Stanley <joel@jms.id.au>

On 9 July 2018 at 15:35, Andrew Jeffery <andrew@aj.id.au> wrote:
> The AST2500 SoC family changes the runtime behaviour of the hardware
> strapping register (SCU70) to write-1-set/write-1-clear, with
> write-1-clear implemented on the "read-only" SoC revision register
> (SCU7C). For the the AST2400, the hardware strapping is
> runtime-configured with read-modify-write semantics.
>
> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
> ---

Hi -- is this a bugfix suitable for 3.0, or something you'd
like to wait until 3.1 ? The commit message sounds like a bugfix...

thanks
-- PMM

On Fri, 13 Jul 2018, at 01:28, Peter Maydell wrote:
> On 9 July 2018 at 15:35, Andrew Jeffery <andrew@aj.id.au> wrote:
> > The AST2500 SoC family changes the runtime behaviour of the hardware
> > strapping register (SCU70) to write-1-set/write-1-clear, with
> > write-1-clear implemented on the "read-only" SoC revision register
> > (SCU7C). For the the AST2400, the hardware strapping is
> > runtime-configured with read-modify-write semantics.
> >
> > Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
> > ---
> 
> Hi -- is this a bugfix suitable for 3.0, or something you'd
> like to wait until 3.1 ? The commit message sounds like a bugfix...

If we could get it into 3.0 that would be great. I ran into a case where the distinction was important so it would be good to have it resolved sooner rather than later.

Cheers,

Andrew

On 12 July 2018 at 17:10, Andrew Jeffery <andrew@aj.id.au> wrote:
> On Fri, 13 Jul 2018, at 01:28, Peter Maydell wrote:
>> On 9 July 2018 at 15:35, Andrew Jeffery <andrew@aj.id.au> wrote:
>> > The AST2500 SoC family changes the runtime behaviour of the hardware
>> > strapping register (SCU70) to write-1-set/write-1-clear, with
>> > write-1-clear implemented on the "read-only" SoC revision register
>> > (SCU7C). For the the AST2400, the hardware strapping is
>> > runtime-configured with read-modify-write semantics.
>> >
>> > Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
>> > ---
>>
>> Hi -- is this a bugfix suitable for 3.0, or something you'd
>> like to wait until 3.1 ? The commit message sounds like a bugfix...
>
> If we could get it into 3.0 that would be great. I ran into a case where the distinction was important so it would be good to have it resolved sooner rather than later.

No problem -- applied to target-arm.next for 3.0 (should go
in before rc1).

thanks
-- PMM