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The timer registers of aclint don't follow the clint layout and can
be mapped on any different offset. As sg2042 uses separated timer
and mswi for its clint, it should follow the aclint spec and have
separated registers.
The previous patch introduced a new type of T-HEAD aclint timer which
has clint timer layout. Although it has the clint timer layout, it
should follow the aclint spec and uses the separated mtime and mtimecmp
regs. So a ABI change is needed to make the timer fit the aclint spec.
To make T-HEAD aclint timer more closer to the aclint spec, use
regs-names to represent the mtimecmp register, which can avoid hack
for unsupport mtime register of T-HEAD aclint timer.
Also, as T-HEAD aclint only supports mtimecmp, it is unnecessary to
implement the whole aclint spec. To make this binding T-HEAD specific,
only add reg-name for existed register. For details, see the discussion
in the last link.
Signed-off-by: Inochi Amaoto <inochiama@outlook.com>
Fixes: 4734449f7311 ("dt-bindings: timer: Add Sophgo sg2042 CLINT timer")
Link: https://lists.infradead.org/pipermail/opensbi/2023-October/005693.html
Link: https://github.com/riscv/riscv-aclint/blob/main/riscv-aclint.adoc
Link: https://lore.kernel.org/all/IA1PR20MB4953F9D77FFC76A9D236922DBBB6A@IA1PR20MB4953.namprd20.prod.outlook.com/
Acked-by: Guo Ren <guoren@kernel.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/IA1PR20MB49531ED1BCC00D6B265C2D10BB86A@IA1PR20MB4953.namprd20.prod.outlook.com
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The clint of Sophgo's sg2042 is based off IP designed by T-HEAD, but
Sophgo changes this IP layout to fit its cpu design and is incompatible
with the standard sifive clint. The timer and ipi device are on the
different address, and can not be handled by the sifive,clint dt-bindings.
If we use the same compatible string for mswi and timer of the sg2042
clint like sifive,clint, the DT may be like this:
mswi: interrupt-controller@94000000 {
compatible = "sophgo,sg2042-clint", "thead,c900-clint";
interrupts-extended = <&cpu1intc 3>;
reg = <0x94000000 0x00010000>;
};
timer: timer@ac000000 {
compatible = "sophgo,sg2042-clint", "thead,c900-clint";
interrupts-extended = <&cpu1intc 7>;
reg = <0xac000000 0x00010000>;
};
Since the address of mswi and timer are different, it is hard to merge
them directly. So we need two DT nodes to handle both devices.
If we use this DT for SBI, it will parse the mswi device in the timer
initialization as the compatible string is the same, so will mswi.
As they are different devices, this incorrect initialization will cause
the system unusable.
There is a more robust ACLINT spec. can handle this situation, but
the spec. seems to be abandoned and will not be frozen in the predictable
future.
So it is not the time to add ACLINT spec in the kernel bindings. Instead,
using vendor bindings is more acceptable.
Add new vendor specific compatible strings to identify timer of sg2042
clint.
Signed-off-by: Inochi Amaoto <inochiama@outlook.com>
Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
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