[PATCH 1/1] rng: detect RISC-V Zkr RNG device in bind method

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: ceec977ba1a9 ("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 --- drivers/rng/riscv_zkr_rng.c | 34 ++++++++++++++++++++++++++-------- 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/rng/riscv_zkr_rng.c b/drivers/rng/riscv_zkr_rng.c index 8c9e111e2e..48a5251988 100644 --- a/drivers/rng/riscv_zkr_rng.c +++ b/drivers/rng/riscv_zkr_rng.c @@ -55,7 +55,7 @@ static int riscv_zkr_read(struct udevice *dev, void *data, size_t len) } break; 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 - * extension is not available this probe function will result - * in an exception. Currently we cannot recover from this. + * If the SBI software has not set mseccfg.sseed=1 or the Zkr extension is not + * available, reading the seed register will result in an exception from which + * this function safely resumes. * * @dev: RNG device * 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; int ret; @@ -87,7 +87,24 @@ static int riscv_zkr_probe(struct udevice *dev) val = read_seed(); set_resume(NULL); 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 { val = read_seed(); @@ -95,7 +112,7 @@ static int riscv_zkr_probe(struct udevice *dev) } while (val == BIST || val == WAIT);

if (val == DEAD) - return -ENODEV; + return -ENOENT;

return 0; } @@ -108,6 +125,7 @@ U_BOOT_DRIVER(riscv_zkr) = { .name = DRIVER_NAME, .id = UCLASS_RNG, .ops = &riscv_zkr_ops, + .bind = riscv_zkr_bind, .probe = riscv_zkr_probe, };