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rng: detect RISC-V Zkr RNG device in bind method

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The existence of devices should be checked in the bind method and not in
the probe method. Adjust the RISC-V Zkr RNG driver accordingly.

Use ENOENT (and not ENODEV) to signal that the device is not available.

Fixes: ceec977ba1 ("rng: Provide a RNG based on the RISC-V Zkr ISA extension")
Reported-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
This commit is contained in:
Heinrich Schuchardt 2023-11-04 08:51:07 +02:00
parent badef4cd4a
commit 1351cd3b4b
1 changed files with 26 additions and 8 deletions
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34
drivers/rng/riscv_zkr_rng.c
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@ -55,7 +55,7 @@ static int riscv_zkr_read(struct udevice *dev, void *data, size_t len)
} }
break; break;
case DEAD: case DEAD:
return -ENODEV; return -ENOENT;
} }
} }
@ -63,16 +63,16 @@ static int riscv_zkr_read(struct udevice *dev, void *data, size_t len)
} }
/** /**
* riscv_zkr_probe() - check if the seed register is available * riscv_zkr_bind() - check if the seed register is available
* *
* If the SBI software has not set mseccfg.sseed=1 or the Zkr * If the SBI software has not set mseccfg.sseed=1 or the Zkr extension is not
* extension is not available this probe function will result * available, reading the seed register will result in an exception from which
* in an exception. Currently we cannot recover from this. * this function safely resumes.
* *
* @dev: RNG device * @dev: RNG device
* Return: 0 if successfully probed * Return: 0 if successfully probed
*/ */
static int riscv_zkr_probe(struct udevice *dev) static int riscv_zkr_bind(struct udevice *dev)
{ {
struct resume_data resume; struct resume_data resume;
int ret; int ret;
@ -87,7 +87,24 @@ static int riscv_zkr_probe(struct udevice *dev)
val = read_seed(); val = read_seed();
set_resume(NULL); set_resume(NULL);
if (ret) if (ret)
return -ENODEV; return -ENOENT;
return 0;
}
/**
* riscv_zkr_probe() - check if entropy is available
*
* The bind method already checked that the seed register can be read without
* excpetiong. Here we wait for the self test to finish and entropy becoming
* available.
*
* @dev: RNG device
* Return: 0 if successfully probed
*/
static int riscv_zkr_probe(struct udevice *dev)
{
u32 val;
do { do {
val = read_seed(); val = read_seed();
@ -95,7 +112,7 @@ static int riscv_zkr_probe(struct udevice *dev)
} while (val == BIST || val == WAIT); } while (val == BIST || val == WAIT);
if (val == DEAD) if (val == DEAD)
return -ENODEV; return -ENOENT;
return 0; return 0;
} }
@ -108,6 +125,7 @@ U_BOOT_DRIVER(riscv_zkr) = {
.name = DRIVER_NAME, .name = DRIVER_NAME,
.id = UCLASS_RNG, .id = UCLASS_RNG,
.ops = &riscv_zkr_ops, .ops = &riscv_zkr_ops,
.bind = riscv_zkr_bind,
.probe = riscv_zkr_probe, .probe = riscv_zkr_probe,
}; };