From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heinrich Schuchardt Date: Fri, 27 Dec 2019 08:51:00 +0100 Subject: [PATCH v5 3/8] stm32mp1: rng: Add a driver for random number generator(rng) device In-Reply-To: <1577381108-6320-4-git-send-email-sughosh.ganu@linaro.org> References: <1577381108-6320-1-git-send-email-sughosh.ganu@linaro.org> <1577381108-6320-4-git-send-email-sughosh.ganu@linaro.org> Message-ID: <633d26d0-a7c9-1984-1f50-e67cc8ed8628@gmx.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 12/26/19 6:25 PM, Sughosh Ganu wrote: > Add a driver for the rng device found on stm32mp1 platforms. The > driver provides a routine for reading the random number seed from the > hardware device. > > Signed-off-by: Sughosh Ganu > Reviewed-by: Patrice Chotard > Acked-by: Patrick Delaunay > --- > Changes since V4: > * Return number of bytes read on a successful read, and a -ve value on > error. > > drivers/rng/Kconfig | 7 ++ > drivers/rng/Makefile | 1 + > drivers/rng/stm32mp1_rng.c | 165 +++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 173 insertions(+) > create mode 100644 drivers/rng/stm32mp1_rng.c > > diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig > index dd44cc0..c9c4751 100644 > --- a/drivers/rng/Kconfig > +++ b/drivers/rng/Kconfig > @@ -5,3 +5,10 @@ config DM_RNG > Enable driver model for random number generator(rng) devices. > This interface is used to initialise the rng device and to > read the random seed from the device. > + > +config RNG_STM32MP1 > + bool "Enable random number generator for STM32MP1" > + depends on ARCH_STM32MP && DM_RNG > + default n > + help > + Enable STM32MP1 rng driver. > diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile > index 311705b..699beb3 100644 > --- a/drivers/rng/Makefile > +++ b/drivers/rng/Makefile > @@ -4,3 +4,4 @@ > # > > obj-$(CONFIG_DM_RNG) += rng-uclass.o > +obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o > diff --git a/drivers/rng/stm32mp1_rng.c b/drivers/rng/stm32mp1_rng.c > new file mode 100644 > index 0000000..56ad848 > --- /dev/null > +++ b/drivers/rng/stm32mp1_rng.c > @@ -0,0 +1,165 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * Copyright (c) 2019, Linaro Limited > + */ > + > +#include > +#include > +#include > +#include > +#include > + > +#include > +#include > +#include > + > +#define RNG_CR 0x00 > +#define RNG_CR_RNGEN BIT(2) > +#define RNG_CR_CED BIT(5) > + > +#define RNG_SR 0x04 > +#define RNG_SR_SEIS BIT(6) > +#define RNG_SR_CEIS BIT(5) > +#define RNG_SR_SECS BIT(2) > +#define RNG_SR_DRDY BIT(0) > + > +#define RNG_DR 0x08 > + > +struct stm32_rng_platdata { > + fdt_addr_t base; > + struct clk clk; > + struct reset_ctl rst; > +}; > + > +static int stm32_rng_read(struct udevice *dev, void *data, size_t len) > +{ > + int retval = 0, i, nbytes; > + u32 sr, count, reg; > + size_t increment; > + struct stm32_rng_platdata *pdata = dev_get_platdata(dev); > + > + /* > + * Only INT_MAX number of bytes can be returned. If more > + * bytes need to be read, the caller must do it in a loop. > + */ > + if (len > INT_MAX) > + len = INT_MAX; > + > + nbytes = len; > + while (len > 0) { > + retval = readl_poll_timeout(pdata->base + RNG_SR, sr, > + sr & RNG_SR_DRDY, 10000); > + if (retval) > + return retval; > + > + if (sr & (RNG_SR_SEIS | RNG_SR_SECS)) { > + /* As per SoC TRM */ > + clrbits_le32(pdata->base + RNG_SR, RNG_SR_SEIS); > + for (i = 0; i < 12; i++) > + readl(pdata->base + RNG_DR); > + if (readl(pdata->base + RNG_SR) & RNG_SR_SEIS) { > + printf("RNG Noise"); > + return -EIO; The SEIS bit indicates a seed error. According to the RM0090 Reference manual for the STM32F429/439 you should clear the SEIS bit and set the RNGEN bit to restart the RNG. https://www.st.com/content/ccc/resource/technical/document/reference_manual/3d/6d/5a/66/b4/99/40/d4/DM00031020.pdf/files/DM00031020.pdf/jcr:content/translations/en.DM00031020.pdf, page 768. So why do you return an error code here? What do you expect the caller to do? Should we check the CEIS flag which indicates a clock error? > + } > + /* start again */ > + continue; > + } > + It took me some time to understand what this loop does. Please, add a comment indicating that we copy up to 16 random bytes from the RNG. Best regards Heinrich > + count = 4; > + while (len && count) { > + reg = readl(pdata->base + RNG_DR); > + memcpy(data, ®, min(len, sizeof(u32))); > + increment = min(len, sizeof(u32)); > + data += increment; > + len -= increment; > + count--; > + } > + } > + > + return nbytes; > +} > + > +static int stm32_rng_init(struct stm32_rng_platdata *pdata) > +{ > + int err; > + > + err = clk_enable(&pdata->clk); > + if (err) > + return err; > + > + /* Disable CED */ > + writel(RNG_CR_RNGEN | RNG_CR_CED, pdata->base + RNG_CR); > + > + /* clear error indicators */ > + writel(0, pdata->base + RNG_SR); > + > + return 0; > +} > + > +static int stm32_rng_cleanup(struct stm32_rng_platdata *pdata) > +{ > + > + writel(0, pdata->base + RNG_CR); > + > + return clk_disable(&pdata->clk); > +} > + > +static int stm32_rng_probe(struct udevice *dev) > +{ > + struct stm32_rng_platdata *pdata = dev_get_platdata(dev); > + > + reset_assert(&pdata->rst); > + udelay(20); > + reset_deassert(&pdata->rst); > + > + return stm32_rng_init(pdata); > +} > + > +static int stm32_rng_remove(struct udevice *dev) > +{ > + struct stm32_rng_platdata *pdata = dev_get_platdata(dev); > + > + return stm32_rng_cleanup(pdata); > +} > + > +static int stm32_rng_ofdata_to_platdata(struct udevice *dev) > +{ > + struct stm32_rng_platdata *pdata = dev_get_platdata(dev); > + int err; > + > + pdata->base = dev_read_addr(dev); > + if (!pdata->base) > + return -ENOMEM; > + > + err = clk_get_by_index(dev, 0, &pdata->clk); > + if (err) > + return err; > + > + err = reset_get_by_index(dev, 0, &pdata->rst); > + if (err) > + return err; > + > + return 0; > +} > + > +static const struct dm_rng_ops stm32_rng_ops = { > + .read = stm32_rng_read, > +}; > + > +static const struct udevice_id stm32_rng_match[] = { > + { > + .compatible = "st,stm32-rng", > + }, > + {}, > +}; > + > +U_BOOT_DRIVER(stm32_rng) = { > + .name = "stm32-rng", > + .id = UCLASS_RNG, > + .of_match = stm32_rng_match, > + .ops = &stm32_rng_ops, > + .probe = stm32_rng_probe, > + .remove = stm32_rng_remove, > + .platdata_auto_alloc_size = sizeof(struct stm32_rng_platdata), > + .ofdata_to_platdata = stm32_rng_ofdata_to_platdata, > +}; >