forked from mirrors/linux
b58a36008b
The last RCU stall fix caused a massive throughput regression of the
hwrng on Raspberry Pi 0 - 3. hwrng_msleep doesn't sleep precisely enough
and usleep_range doesn't allow scheduling. So try to restore the
best possible throughput by introducing hwrng_yield which interruptable
sleeps for one jiffy.
Some performance measurements on Raspberry Pi 3B+ (arm64/defconfig):
sudo dd if=/dev/hwrng of=/dev/null count=1 bs=10000
cpu_relax ~138025 Bytes / sec
hwrng_msleep(1000) ~13 Bytes / sec
hwrng_yield ~2510 Bytes / sec
Fixes: 96cb9d0554 ("hwrng: bcm2835 - use hwrng_msleep() instead of cpu_relax()")
Link: https://lore.kernel.org/linux-arm-kernel/bc97ece5-44a3-4c4e-77da-2db3eb66b128@gmx.net/
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
68 lines
2.3 KiB
C
68 lines
2.3 KiB
C
/*
|
|
Hardware Random Number Generator
|
|
|
|
Please read Documentation/admin-guide/hw_random.rst for details on use.
|
|
|
|
----------------------------------------------------------
|
|
This software may be used and distributed according to the terms
|
|
of the GNU General Public License, incorporated herein by reference.
|
|
|
|
*/
|
|
|
|
#ifndef LINUX_HWRANDOM_H_
|
|
#define LINUX_HWRANDOM_H_
|
|
|
|
#include <linux/completion.h>
|
|
#include <linux/types.h>
|
|
#include <linux/list.h>
|
|
#include <linux/kref.h>
|
|
|
|
/**
|
|
* struct hwrng - Hardware Random Number Generator driver
|
|
* @name: Unique RNG name.
|
|
* @init: Initialization callback (can be NULL).
|
|
* @cleanup: Cleanup callback (can be NULL).
|
|
* @data_present: Callback to determine if data is available
|
|
* on the RNG. If NULL, it is assumed that
|
|
* there is always data available. *OBSOLETE*
|
|
* @data_read: Read data from the RNG device.
|
|
* Returns the number of lower random bytes in "data".
|
|
* Must not be NULL. *OBSOLETE*
|
|
* @read: New API. drivers can fill up to max bytes of data
|
|
* into the buffer. The buffer is aligned for any type
|
|
* and max is a multiple of 4 and >= 32 bytes.
|
|
* @priv: Private data, for use by the RNG driver.
|
|
* @quality: Estimation of true entropy in RNG's bitstream
|
|
* (in bits of entropy per 1024 bits of input;
|
|
* valid values: 1 to 1024, or 0 for maximum).
|
|
*/
|
|
struct hwrng {
|
|
const char *name;
|
|
int (*init)(struct hwrng *rng);
|
|
void (*cleanup)(struct hwrng *rng);
|
|
int (*data_present)(struct hwrng *rng, int wait);
|
|
int (*data_read)(struct hwrng *rng, u32 *data);
|
|
int (*read)(struct hwrng *rng, void *data, size_t max, bool wait);
|
|
unsigned long priv;
|
|
unsigned short quality;
|
|
|
|
/* internal. */
|
|
struct list_head list;
|
|
struct kref ref;
|
|
struct completion cleanup_done;
|
|
struct completion dying;
|
|
};
|
|
|
|
struct device;
|
|
|
|
/** Register a new Hardware Random Number Generator driver. */
|
|
extern int hwrng_register(struct hwrng *rng);
|
|
extern int devm_hwrng_register(struct device *dev, struct hwrng *rng);
|
|
/** Unregister a Hardware Random Number Generator driver. */
|
|
extern void hwrng_unregister(struct hwrng *rng);
|
|
extern void devm_hwrng_unregister(struct device *dve, struct hwrng *rng);
|
|
|
|
extern long hwrng_msleep(struct hwrng *rng, unsigned int msecs);
|
|
extern long hwrng_yield(struct hwrng *rng);
|
|
|
|
#endif /* LINUX_HWRANDOM_H_ */
|