Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1469085 > unrolled thread

Re: [PATCH v2 2/2] HWRNG: thunderx: Add Cavium HWRNG driver for ThunderX SoC.

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: [PATCH v2 2/2] HWRNG: thunderx: Add Cavium HWRNG driver for  ThunderX SoC. Corentin LABBE <clabbe.montjoie@gmail.com> - 2016-08-24 07:50 +0200
    Re: [PATCH v2 2/2] HWRNG: thunderx: Add Cavium HWRNG driver for ThunderX  SoC. David Daney <ddaney.cavm@gmail.com> - 2016-08-25 01:10 +0200

#1469085 — Re: [PATCH v2 2/2] HWRNG: thunderx: Add Cavium HWRNG driver for ThunderX SoC.

Hello

> +/* Read data from the RNG unit */
> +static int cavium_rng_read(struct hwrng *rng, void *dat, size_t max, bool wait)
> +{
> +	struct cavium_rng *p = container_of(rng, struct cavium_rng, ops);
> +	unsigned int size = max;
> +
> +	while (size >= 8) {
> +		*((u64 *)dat) = readq(p->result);
> +		size -= 8;
> +		dat += 8;
> +	}

I think you could use readsq()
This will increase throughput

Regards

LABBE Corentin

[toc] | [next] | [standalone]

#1469774 — Re: [PATCH v2 2/2] HWRNG: thunderx: Add Cavium HWRNG driver for ThunderX SoC.

On 08/23/2016 10:46 PM, Corentin LABBE wrote:
> Hello
>
>> +/* Read data from the RNG unit */
>> +static int cavium_rng_read(struct hwrng *rng, void *dat, size_t max, bool wait)
>> +{
>> +	struct cavium_rng *p = container_of(rng, struct cavium_rng, ops);
>> +	unsigned int size = max;
>> +
>> +	while (size >= 8) {
>> +		*((u64 *)dat) = readq(p->result);
>> +		size -= 8;
>> +		dat += 8;
>> +	}
>
> I think you could use readsq()
> This will increase throughput

If you look at the implementation of readsq(), you will see that it is a 
similar loop.  Since the overhead is primarily I/O latency from the RNG 
hardware, the throughput cannot really be changed with micro 
optimizations to this simple loop.

Also, on big-endian kernels, it appears that a loop of readq() and 
readsq() will give different results as readq will byte swap the result 
and readsq does not.  Since this is a RNG, the byte swapping is not 
important, but it is a difference.

Because of this, I think it should be acceptable to stick with the loop 
we currently have.

If the hwrng maintainers want to change the loop, to a readsq(), we 
might investigate this more.

Thanks,
David Daney

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web