Re: [PATCH 08/12] hwrng: bcm2835-rng: Abstract I/O accessors
On 11/03/2017 01:19 PM, Eric Anholt wrote:
> Florian Fainelli writes:
>
>> In preparation for allowing BCM63xx to use this driver, we abstract I/O
>> accessors such that we can easily change those later on.
>>
>> Signed-off-by: Florian Fainelli
>> ---
>> drivers/char/hw_random/bcm2835-rng.c | 27 +++
>> 1 file changed, 19 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/char/hw_random/bcm2835-rng.c
>> b/drivers/char/hw_random/bcm2835-rng.c
>> index 35928efb52e7..500275d55044 100644
>> --- a/drivers/char/hw_random/bcm2835-rng.c
>> +++ b/drivers/char/hw_random/bcm2835-rng.c
>> @@ -42,6 +42,17 @@ static inline struct bcm2835_rng_priv *to_rng_priv(struct
>> hwrng *rng)
>> return container_of(rng, struct bcm2835_rng_priv, rng);
>> }
>>
>> +static inline u32 rng_readl(struct bcm2835_rng_priv *priv, u32 offset)
>> +{
>> +return readl(priv->base + offset);
>> +}
>> +
>> +static inline void rng_writel(struct bcm2835_rng_priv *priv, u32 val,
>> + u32 offset)
>> +{
>> +writel(val, priv->base + offset);
>> +}
>> +
>> static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
>> bool wait)
>> {
>> @@ -49,18 +60,18 @@ static int bcm2835_rng_read(struct hwrng *rng, void
>> *buf, size_t max,
>> u32 max_words = max / sizeof(u32);
>> u32 num_words, count;
>>
>> -while ((__raw_readl(priv->base + RNG_STATUS) >> 24) == 0) {
>> +while ((rng_readl(priv, RNG_STATUS) >> 24) == 0) {
>> if (!wait)
>> return 0;
>> cpu_relax();
>> }
>
> What was the difference between the __raw_readl and readl that's now
> being done in the new call? Is it important?
readl() on ARM contains a memory barrier, which has therefore stronger
ordering guarantees than __raw_readl() which does not.
In practice I don't think this makes a whole lot of difference in that
the above loop does not even have a barrier outside of it to try to have
any sort of ordering guarantee so it seems to me like this may be an
oversight.
I took the liberty to use the stronger operation here because it seems
to me like this is what is desired, or at least won't cause functional
problems, and because I am not intimately familiar with the 2835 busing
architecture. I know for a thing that the Broadcom STB and DSL busses
(named GISB and UBUS respectively) do not require such barriers since
they do not re-order transactions and are non-posted.
>
>> /* set warm-up count & enable */
>> -__raw_writel(RNG_WARMUP_COUNT, priv->base + RNG_STATUS);
>> -__raw_writel(RNG_RBGEN, priv->base + RNG_CTRL);
>> +rng_writel(priv, RNG_WARMUP_COUNT, RNG_STATUS);
>> +rng_writel(priv, RNG_RBGEN, RNG_CTRL);
>
> Similar question.
And here we definitively are not in a hot-path so the more "ordered"
variant is acceptable it seems.
--
Florian
Re: [PATCH 08/12] hwrng: bcm2835-rng: Abstract I/O accessors
Florian Fainelli writes:
> In preparation for allowing BCM63xx to use this driver, we abstract I/O
> accessors such that we can easily change those later on.
>
> Signed-off-by: Florian Fainelli
> ---
> drivers/char/hw_random/bcm2835-rng.c | 27 +++
> 1 file changed, 19 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/char/hw_random/bcm2835-rng.c
> b/drivers/char/hw_random/bcm2835-rng.c
> index 35928efb52e7..500275d55044 100644
> --- a/drivers/char/hw_random/bcm2835-rng.c
> +++ b/drivers/char/hw_random/bcm2835-rng.c
> @@ -42,6 +42,17 @@ static inline struct bcm2835_rng_priv *to_rng_priv(struct
> hwrng *rng)
> return container_of(rng, struct bcm2835_rng_priv, rng);
> }
>
> +static inline u32 rng_readl(struct bcm2835_rng_priv *priv, u32 offset)
> +{
> + return readl(priv->base + offset);
> +}
> +
> +static inline void rng_writel(struct bcm2835_rng_priv *priv, u32 val,
> + u32 offset)
> +{
> + writel(val, priv->base + offset);
> +}
> +
> static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
> bool wait)
> {
> @@ -49,18 +60,18 @@ static int bcm2835_rng_read(struct hwrng *rng, void *buf,
> size_t max,
> u32 max_words = max / sizeof(u32);
> u32 num_words, count;
>
> - while ((__raw_readl(priv->base + RNG_STATUS) >> 24) == 0) {
> + while ((rng_readl(priv, RNG_STATUS) >> 24) == 0) {
> if (!wait)
> return 0;
> cpu_relax();
> }
What was the difference between the __raw_readl and readl that's now
being done in the new call? Is it important?
> /* set warm-up count & enable */
> - __raw_writel(RNG_WARMUP_COUNT, priv->base + RNG_STATUS);
> - __raw_writel(RNG_RBGEN, priv->base + RNG_CTRL);
> + rng_writel(priv, RNG_WARMUP_COUNT, RNG_STATUS);
> + rng_writel(priv, RNG_RBGEN, RNG_CTRL);
Similar question.
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[PATCH 08/12] hwrng: bcm2835-rng: Abstract I/O accessors
In preparation for allowing BCM63xx to use this driver, we abstract I/O
accessors such that we can easily change those later on.
Signed-off-by: Florian Fainelli
---
drivers/char/hw_random/bcm2835-rng.c | 27 +++
1 file changed, 19 insertions(+), 8 deletions(-)
diff --git a/drivers/char/hw_random/bcm2835-rng.c
b/drivers/char/hw_random/bcm2835-rng.c
index 35928efb52e7..500275d55044 100644
--- a/drivers/char/hw_random/bcm2835-rng.c
+++ b/drivers/char/hw_random/bcm2835-rng.c
@@ -42,6 +42,17 @@ static inline struct bcm2835_rng_priv *to_rng_priv(struct
hwrng *rng)
return container_of(rng, struct bcm2835_rng_priv, rng);
}
+static inline u32 rng_readl(struct bcm2835_rng_priv *priv, u32 offset)
+{
+ return readl(priv->base + offset);
+}
+
+static inline void rng_writel(struct bcm2835_rng_priv *priv, u32 val,
+ u32 offset)
+{
+ writel(val, priv->base + offset);
+}
+
static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
bool wait)
{
@@ -49,18 +60,18 @@ static int bcm2835_rng_read(struct hwrng *rng, void *buf,
size_t max,
u32 max_words = max / sizeof(u32);
u32 num_words, count;
- while ((__raw_readl(priv->base + RNG_STATUS) >> 24) == 0) {
+ while ((rng_readl(priv, RNG_STATUS) >> 24) == 0) {
if (!wait)
return 0;
cpu_relax();
}
- num_words = readl(priv->base + RNG_STATUS) >> 24;
+ num_words = rng_readl(priv, RNG_STATUS) >> 24;
if (num_words > max_words)
num_words = max_words;
for (count = 0; count < num_words; count++)
- ((u32 *)buf)[count] = readl(priv->base + RNG_DATA);
+ ((u32 *)buf)[count] = rng_readl(priv, RNG_DATA);
return num_words * sizeof(u32);
}
@@ -77,14 +88,14 @@ static int bcm2835_rng_init(struct hwrng *rng)
if (priv->mask_interrupts) {
/* mask the interrupt */
- val = readl(priv->base + RNG_INT_MASK);
+ val = rng_readl(priv, RNG_INT_MASK);
val |= RNG_INT_OFF;
- writel(val, priv->base + RNG_INT_MASK);
+ rng_writel(priv, val, RNG_INT_MASK);
}
/* set warm-up count & enable */
- __raw_writel(RNG_WARMUP_COUNT, priv->base + RNG_STATUS);
- __raw_writel(RNG_RBGEN, priv->base + RNG_CTRL);
+ rng_writel(priv, RNG_WARMUP_COUNT, RNG_STATUS);
+ rng_writel(priv, RNG_RBGEN, RNG_CTRL);
return 0;
}
@@ -94,7 +105,7 @@ static void bcm2835_rng_cleanup(struct hwrng *rng)
struct bcm2835_rng_priv *priv = to_rng_priv(rng);
/* disable rng hardware */
- __raw_writel(0, priv->base + RNG_CTRL);
+ rng_writel(priv, 0, RNG_CTRL);
clk_disable_unprepare(priv->clk);
}
--
2.9.3
