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Date:   Wed, 06 Dec 2017 14:42:56 +0100
From:   Łukasz Stelmach <l.stelmach@...sung.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     robh+dt@...nel.org, Stephan Mueller <smueller@...onox.de>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Kukjin Kim <kgene@...nel.org>, linux-crypto@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Bartłomiej Żołnierkiewicz 
        <b.zolnierkie@...sung.com>
Subject: Re: [PATCH 1/3] crypto: exynos - Support Exynos5250+ SoCs

It was <2017-12-05 wto 14:34>, when Krzysztof Kozlowski wrote:
> On Tue, Dec 5, 2017 at 1:35 PM, Łukasz Stelmach <l.stelmach@...sung.com> wrote:
>> Add support for PRNG in Exynos5250+ SoCs.
>>
>> Signed-off-by: Łukasz Stelmach <l.stelmach@...sung.com>
>> ---
>>  .../bindings/crypto/samsung,exynos-rng4.txt        |  4 ++-
>>  drivers/crypto/exynos-rng.c                        | 36 ++++++++++++++++++++--
>>  2 files changed, 36 insertions(+), 4 deletions(-)
>>
>> diff --git
>> a/Documentation/devicetree/bindings/crypto/samsung,exynos-rng4.txt
>> b/Documentation/devicetree/bindings/crypto/samsung,exynos-rng4.txt
>> index 4ca8dd4d7e66..a13fbdb4bd88 100644
>> --- a/Documentation/devicetree/bindings/crypto/samsung,exynos-rng4.txt
>> +++ b/Documentation/devicetree/bindings/crypto/samsung,exynos-rng4.txt
>> @@ -2,7 +2,9 @@ Exynos Pseudo Random Number Generator
>>
>>  Required properties:
>>
>> -- compatible  : Should be "samsung,exynos4-rng".
>> +- compatible  : One of:
>> +                - "samsung,exynos4-rng" for Exynos4210 and Exynos4412
>> +                - "samsung,exynos5250-prng" for Exynos5250+
>>  - reg         : Specifies base physical address and size of the registers map.
>>  - clocks      : Phandle to clock-controller plus clock-specifier pair.
>>  - clock-names : "secss" as a clock name.
>> diff --git a/drivers/crypto/exynos-rng.c b/drivers/crypto/exynos-rng.c
>> index 451620b475a0..894ef93ef5ec 100644
>> --- a/drivers/crypto/exynos-rng.c
>> +++ b/drivers/crypto/exynos-rng.c
>> @@ -22,12 +22,17 @@
>>  #include <linux/err.h>
>>  #include <linux/io.h>
>>  #include <linux/module.h>
>> +#include <linux/of_device.h>
>>  #include <linux/platform_device.h>
>>
>>  #include <crypto/internal/rng.h>
>>
>>  #define EXYNOS_RNG_CONTROL             0x0
>>  #define EXYNOS_RNG_STATUS              0x10
>> +
>> +#define EXYNOS_RNG_SEED_CONF           0x14
>> +#define EXYNOS_RNG_GEN_PRNG            0x02
>
> Use BIT(1) instead.
>
>> +
>>  #define EXYNOS_RNG_SEED_BASE           0x140
>>  #define EXYNOS_RNG_SEED(n)             (EXYNOS_RNG_SEED_BASE + (n * 0x4))
>>  #define EXYNOS_RNG_OUT_BASE            0x160
>> @@ -43,6 +48,11 @@
>>  #define EXYNOS_RNG_SEED_REGS           5
>>  #define EXYNOS_RNG_SEED_SIZE           (EXYNOS_RNG_SEED_REGS * 4)
>>
>> +enum exynos_prng_type {
>> +       EXYNOS_PRNG_TYPE4 = 4,
>> +       EXYNOS_PRNG_TYPE5 = 5,
>
> That's unusual numbering and naming, so just:
> enum exynos_prng_type {
>       EXYNOS_PRNG_EXYNOS4,
>       EXYNOS_PRNG_EXYNOS5,
> };
>
> Especially that TYPE4 and TYPE5 suggest so kind of sub-type (like
> versions of some IP blocks, e.g. MFC) but it is just the family of
> Exynos.

Half done. I've changed TYPE to EXYNOS.

I used explicit numbering in the enum because I want both values to act
same true-false-wise. If one is 0 this condition is not met.

>> +};
>> +
>>  /*
>>   * Driver re-seeds itself with generated random numbers to increase
>>   * the randomness.
>> @@ -63,6 +73,7 @@ struct exynos_rng_ctx {
>>  /* Device associated memory */
>>  struct exynos_rng_dev {
>>         struct device                   *dev;
>> +       enum exynos_prng_type           type;
>>         void __iomem                    *mem;
>>         struct clk                      *clk;
>>         /* Generated numbers stored for seeding during resume */
>> @@ -160,8 +171,13 @@ static int exynos_rng_get_random(struct exynos_rng_dev *rng,
>>  {
>>         int retry = EXYNOS_RNG_WAIT_RETRIES;
>>
>> -       exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START,
>> -                         EXYNOS_RNG_CONTROL);
>> +       if (rng->type == EXYNOS_PRNG_TYPE4) {
>> +               exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START,
>> +                                 EXYNOS_RNG_CONTROL);
>> +       } else if (rng->type == EXYNOS_PRNG_TYPE5) {
>> +               exynos_rng_writel(rng, EXYNOS_RNG_GEN_PRNG,
>> +                                 EXYNOS_RNG_SEED_CONF);
>> +       }
>>
>>         while (!(exynos_rng_readl(rng,
>>                         EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) && --retry)
>> @@ -279,6 +295,13 @@ static int exynos_rng_probe(struct platform_device *pdev)
>>         if (!rng)
>>                 return -ENOMEM;
>>
>> +       rng->type = (enum exynos_prng_type)of_device_get_match_data(&pdev->dev);
>> +       if (rng->type != EXYNOS_PRNG_TYPE4 &&
>> +           rng->type != EXYNOS_PRNG_TYPE5) {
>> +               dev_err(&pdev->dev, "Unsupported PRNG type: %d", rng->type);
>> +               return -ENOTSUPP;
>> +       }
>> +
>>         rng->dev = &pdev->dev;
>>         rng->clk = devm_clk_get(&pdev->dev, "secss");
>>         if (IS_ERR(rng->clk)) {
>> @@ -300,7 +323,10 @@ static int exynos_rng_probe(struct platform_device *pdev)
>>                 dev_err(&pdev->dev,
>>                         "Couldn't register rng crypto alg: %d\n", ret);
>>                 exynos_rng_dev = NULL;
>> -       }
>> +       } else
>
> Missing {} around else clause. Probably checkpatch should point it.

It doesn't. Fixed.

>> +               dev_info(&pdev->dev,
>> +                        "Exynos Pseudo Random Number Generator (type:%d)\n",
>
> dev_dbg, this is not that important information to affect the boot time.

Quite many devices report their presence during boot with such
messages. For example:

[    3.390247] exynos-ehci 12110000.usb: EHCI Host Controller
[    3.395493] exynos-ehci 12110000.usb: new USB bus registered, assigned bus number 1
[    3.403702] exynos-ehci 12110000.usb: irq 80, io mem 0x12110000
[    3.431793] exynos-ehci 12110000.usb: USB 2.0 started, EHCI 1.00

From my experience it isn't printk() itself that slows down boot but the
serial console.

-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics

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