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    SubjectRe: [PATCH 07/12] hwrng: bcm2835-rng: Manage an optional clock

    > Florian Fainelli <f.fainelli@gmail.com> hat am 4. November 2017 um 18:59 geschrieben:
    >
    >
    > Hi Stefan,
    >
    > On 11/04/2017 06:50 AM, Stefan Wahren wrote:
    > > Hi Florian,
    > >
    > >> Florian Fainelli <f.fainelli@gmail.com> hat am 2. November 2017 um 02:04 geschrieben:
    > >>
    > >>
    > >> One of the last steps before bcm63xx-rng can be eliminated is to manage
    > >> a clock during hwrng::init and hwrng::cleanup, so fetch it in the probe
    > >> function, and manage it during these two steps when valid.
    > >>
    > >> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
    > >> ---
    > >> drivers/char/hw_random/bcm2835-rng.c | 14 ++++++++++++++
    > >> 1 file changed, 14 insertions(+)
    > >>
    > >> diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c
    > >> index ed20e0b6b7ae..35928efb52e7 100644
    > >> --- a/drivers/char/hw_random/bcm2835-rng.c
    > >> +++ b/drivers/char/hw_random/bcm2835-rng.c
    > >> @@ -15,6 +15,7 @@
    > >> #include <linux/of_platform.h>
    > >> #include <linux/platform_device.h>
    > >> #include <linux/printk.h>
    > >> +#include <linux/clk.h>
    > >>
    > >> #define RNG_CTRL 0x0
    > >> #define RNG_STATUS 0x4
    > >> @@ -33,6 +34,7 @@ struct bcm2835_rng_priv {
    > >> struct hwrng rng;
    > >> void __iomem *base;
    > >> bool mask_interrupts;
    > >> + struct clk *clk;
    > >> };
    > >>
    > >> static inline struct bcm2835_rng_priv *to_rng_priv(struct hwrng *rng)
    > >> @@ -67,6 +69,11 @@ static int bcm2835_rng_init(struct hwrng *rng)
    > >> {
    > >> struct bcm2835_rng_priv *priv = to_rng_priv(rng);
    > >> u32 val;
    > >> + int ret;
    > >> +
    > >> + ret = clk_prepare_enable(priv->clk);
    > >> + if (ret)
    > >> + return ret;
    > >>
    > >> if (priv->mask_interrupts) {
    > >> /* mask the interrupt */
    > >> @@ -88,6 +95,8 @@ static void bcm2835_rng_cleanup(struct hwrng *rng)
    > >>
    > >> /* disable rng hardware */
    > >> __raw_writel(0, priv->base + RNG_CTRL);
    > >> +
    > >> + clk_disable_unprepare(priv->clk);
    > >> }
    > >>
    > >> struct bcm2835_rng_of_data {
    > >> @@ -130,6 +139,11 @@ static int bcm2835_rng_probe(struct platform_device *pdev)
    > >> return PTR_ERR(priv->base);
    > >> }
    > >>
    > >> + /* Clock is optional on most platforms */
    > >> + priv->clk = devm_clk_get(dev, NULL);
    > >> + if (IS_ERR(priv->clk))
    > >> + priv->clk = NULL;
    > >
    > > at least in case of EPROBE_DEFERED this isn't the expected behavior. Maybe we should better trigger on non-existing clock?
    >
    > Good point, so more like:
    >
    > if (IS_ERR(priv->clk) && PTR_ERR(priv->clk) == -ENODEV)?

    Unfortunately we need to return the error in all other cases. Please take a look at devm_usb_get_phy in dwc2 [1]. AFAIK we don't need to take care of ENXIO in our case.

    http://elixir.free-electrons.com/linux/latest/source/drivers/usb/dwc2/platform.c#L247

    >
    > --
    > Florian
    >
    > _______________________________________________
    > linux-arm-kernel mailing list
    > linux-arm-kernel@lists.infradead.org
    > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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