From: Lee Jones <lee.jones@linaro.org>
To: Daniel Thompson <daniel.thompson@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kernel@stlinux.com,
herbert@gondor.apana.org.au, peter@korsgaard.com,
festevam@gmail.com, pankaj.dev@st.com
Subject: Re: [PATCH 2/3] hwrng: st: Report correct FIFO size
Date: Tue, 6 Oct 2015 16:23:26 +0100 [thread overview]
Message-ID: <20151006152326.GE17172@x1> (raw)
In-Reply-To: <5613ED47.1040608@linaro.org>
On Tue, 06 Oct 2015, Daniel Thompson wrote:
> On 06/10/15 15:43, Lee Jones wrote:
> >The values supplied to the 'read random data from FIFO' arithmetic
> >are not correct. The value fed in to initialise the iterator
> >describes the FIFO depth, but then the iterator is treated in
> >Bytes and subsequently increased by 2 in value for every read
> >word. This means only 4 of the 8 available values are being read
> >during each invocation of .read().
> >
> >This change increased the device bandwidth by a factor of 2.
> >
> >Reported-by: Daniel Thompson <daniel.thompson@linaro.org>
> >Signed-off-by: Lee Jones <lee.jones@linaro.org>
> >---
> > drivers/char/hw_random/st-rng.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> >diff --git a/drivers/char/hw_random/st-rng.c b/drivers/char/hw_random/st-rng.c
> >index 8c8a435..44480fe 100644
> >--- a/drivers/char/hw_random/st-rng.c
> >+++ b/drivers/char/hw_random/st-rng.c
> >@@ -29,8 +29,9 @@
> > #define ST_RNG_STATUS_BAD_ALTERNANCE BIT(1)
> > #define ST_RNG_STATUS_FIFO_FULL BIT(5)
> >
> >-#define ST_RNG_FIFO_SIZE 8
> > #define ST_RNG_SAMPLE_SIZE 2 /* 2 Byte (16bit) samples */
> >+#define ST_RNG_FIFO_DEPTH 8
> >+#define ST_RNG_FIFO_SIZE (ST_RNG_FIFO_DEPTH * ST_RNG_SAMPLE_SIZE)
> >
> > /* Samples are available every 0.667us, which we round to 1us */
> > #define ST_RNG_FILL_FIFO_TIMEOUT (1 * (ST_RNG_FIFO_SIZE / ST_RNG_SAMPLE_SIZE))
>
> This change doubles the timeout and doesn't mention it in the
> changelog.
The next patch renders this point moot.
> Changing the order of 2/3 and 3/3 would avoid this.
Right, if this is a real concern the patches can be applied in a
different order.
> Other than that:
>
> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Thanking you.
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
next prev parent reply other threads:[~2015-10-06 15:23 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-06 14:43 [RESEND 1/3] hwrng: st: dt: Fix trivial typo in node address Lee Jones
2015-10-06 14:43 ` [PATCH 2/3] hwrng: st: Report correct FIFO size Lee Jones
2015-10-06 15:48 ` Daniel Thompson
2015-10-06 15:23 ` Lee Jones [this message]
2015-10-06 14:44 ` [PATCH 3/3] hwrng: st: Use real-world device timings for timeout Lee Jones
2015-10-06 19:37 ` Russell King - ARM Linux
2015-10-06 20:51 ` Lee Jones
2015-10-06 20:56 ` Russell King - ARM Linux
2015-10-07 7:53 ` Lee Jones
2015-10-06 15:24 ` [RESEND 1/3] hwrng: st: dt: Fix trivial typo in node address Herbert Xu
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