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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-05 20:26:43 +07:00
hwrng: timeriomem - Improve performance for sub-jiffie update periods
Some hardware RNGs provide a single register for obtaining random data. Instead of signaling when new data is available, the reader must wait a fixed amount of time between reads for new data to be generated. timeriomem_rng implements this scheme with the period specified in platform data or device tree. While the period is specified in microseconds, the implementation used a standard timer which has a minimum delay of 1 jiffie and caused a significant bottleneck for devices that can update at 1us. By switching to an hrtimer, 1us periods now only delay at most 2us per read. Signed-off-by: Rick Altherr <raltherr@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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@ -21,23 +21,24 @@
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*/
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*/
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#include <linux/completion.h>
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#include <linux/completion.h>
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#include <linux/delay.h>
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#include <linux/hrtimer.h>
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#include <linux/hw_random.h>
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#include <linux/hw_random.h>
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#include <linux/io.h>
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#include <linux/io.h>
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#include <linux/jiffies.h>
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#include <linux/ktime.h>
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#include <linux/module.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/of.h>
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#include <linux/platform_device.h>
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#include <linux/platform_device.h>
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#include <linux/slab.h>
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#include <linux/slab.h>
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#include <linux/time.h>
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#include <linux/timeriomem-rng.h>
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#include <linux/timeriomem-rng.h>
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#include <linux/timer.h>
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struct timeriomem_rng_private {
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struct timeriomem_rng_private {
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void __iomem *io_base;
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void __iomem *io_base;
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unsigned int expires;
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ktime_t period;
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unsigned int period;
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unsigned int present:1;
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unsigned int present:1;
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struct timer_list timer;
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struct hrtimer timer;
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struct completion completion;
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struct completion completion;
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struct hwrng rng_ops;
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struct hwrng rng_ops;
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@ -48,10 +49,13 @@ static int timeriomem_rng_read(struct hwrng *hwrng, void *data,
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{
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{
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struct timeriomem_rng_private *priv =
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struct timeriomem_rng_private *priv =
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container_of(hwrng, struct timeriomem_rng_private, rng_ops);
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container_of(hwrng, struct timeriomem_rng_private, rng_ops);
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unsigned long cur;
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int retval = 0;
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s32 delay;
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int period_us = ktime_to_us(priv->period);
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/* The RNG provides 32-bit per read. Ensure there is enough space. */
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/*
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* The RNG provides 32-bits per read. Ensure there is enough space for
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* at minimum one read.
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*/
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if (max < sizeof(u32))
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if (max < sizeof(u32))
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return 0;
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return 0;
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@ -66,33 +70,44 @@ static int timeriomem_rng_read(struct hwrng *hwrng, void *data,
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wait_for_completion(&priv->completion);
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wait_for_completion(&priv->completion);
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do {
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/*
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* After the first read, all additional reads will need to wait
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* for the RNG to generate new data. Since the period can have
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* a wide range of values (1us to 1s have been observed), allow
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* for 1% tolerance in the sleep time rather than a fixed value.
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*/
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if (retval > 0)
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usleep_range(period_us,
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period_us + min(1, period_us / 100));
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*(u32 *)data = readl(priv->io_base);
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*(u32 *)data = readl(priv->io_base);
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retval += sizeof(u32);
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data += sizeof(u32);
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max -= sizeof(u32);
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} while (wait && max > sizeof(u32));
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/*
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/*
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* Block any new callers until the RNG has had time to generate new
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* Block any new callers until the RNG has had time to generate new
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* data.
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* data.
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*/
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*/
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cur = jiffies;
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delay = cur - priv->expires;
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delay = priv->period - (delay % priv->period);
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priv->expires = cur + delay;
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priv->present = 0;
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priv->present = 0;
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reinit_completion(&priv->completion);
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reinit_completion(&priv->completion);
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mod_timer(&priv->timer, priv->expires);
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hrtimer_forward_now(&priv->timer, priv->period);
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hrtimer_restart(&priv->timer);
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return 4;
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return retval;
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}
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}
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static void timeriomem_rng_trigger(unsigned long data)
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static enum hrtimer_restart timeriomem_rng_trigger(struct hrtimer *timer)
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{
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{
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struct timeriomem_rng_private *priv
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struct timeriomem_rng_private *priv
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= (struct timeriomem_rng_private *)data;
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= container_of(timer, struct timeriomem_rng_private, timer);
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priv->present = 1;
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priv->present = 1;
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complete(&priv->completion);
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complete(&priv->completion);
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return HRTIMER_NORESTART;
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}
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}
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static int timeriomem_rng_probe(struct platform_device *pdev)
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static int timeriomem_rng_probe(struct platform_device *pdev)
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@ -140,43 +155,33 @@ static int timeriomem_rng_probe(struct platform_device *pdev)
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period = pdata->period;
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period = pdata->period;
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}
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}
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priv->period = usecs_to_jiffies(period);
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priv->period = ns_to_ktime(period * NSEC_PER_USEC);
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if (priv->period < 1) {
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dev_err(&pdev->dev, "period is less than one jiffy\n");
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return -EINVAL;
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}
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priv->expires = jiffies;
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priv->present = 1;
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init_completion(&priv->completion);
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init_completion(&priv->completion);
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complete(&priv->completion);
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hrtimer_init(&priv->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
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priv->timer.function = timeriomem_rng_trigger;
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setup_timer(&priv->timer, timeriomem_rng_trigger, (unsigned long)priv);
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priv->rng_ops.name = dev_name(&pdev->dev);
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priv->rng_ops.name = dev_name(&pdev->dev);
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priv->rng_ops.read = timeriomem_rng_read;
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priv->rng_ops.read = timeriomem_rng_read;
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priv->io_base = devm_ioremap_resource(&pdev->dev, res);
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priv->io_base = devm_ioremap_resource(&pdev->dev, res);
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if (IS_ERR(priv->io_base)) {
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if (IS_ERR(priv->io_base)) {
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err = PTR_ERR(priv->io_base);
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return PTR_ERR(priv->io_base);
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goto out_timer;
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}
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}
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/* Assume random data is already available. */
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priv->present = 1;
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complete(&priv->completion);
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err = hwrng_register(&priv->rng_ops);
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err = hwrng_register(&priv->rng_ops);
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if (err) {
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if (err) {
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dev_err(&pdev->dev, "problem registering\n");
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dev_err(&pdev->dev, "problem registering\n");
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goto out_timer;
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return err;
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}
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}
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dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
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dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
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priv->io_base, period);
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priv->io_base, period);
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return 0;
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return 0;
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out_timer:
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del_timer_sync(&priv->timer);
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return err;
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}
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}
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static int timeriomem_rng_remove(struct platform_device *pdev)
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static int timeriomem_rng_remove(struct platform_device *pdev)
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@ -184,8 +189,7 @@ static int timeriomem_rng_remove(struct platform_device *pdev)
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struct timeriomem_rng_private *priv = platform_get_drvdata(pdev);
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struct timeriomem_rng_private *priv = platform_get_drvdata(pdev);
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hwrng_unregister(&priv->rng_ops);
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hwrng_unregister(&priv->rng_ops);
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hrtimer_cancel(&priv->timer);
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del_timer_sync(&priv->timer);
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return 0;
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return 0;
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}
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}
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