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SubjectRe: [PATCH v7 2/3] hw_random: cctrng: introduce Arm CryptoCell driver
Hi Hadar,

On Fri, Mar 27, 2020 at 7:11 AM Hadar Gat <hadar.gat@arm.com> wrote:
> Introduce low level Arm CryptoCell TRNG HW support.
>
> Signed-off-by: Hadar Gat <hadar.gat@arm.com>

Thanks for your patch!

> --- /dev/null
> +++ b/drivers/char/hw_random/cctrng.c

> +static int cctrng_probe(struct platform_device *pdev)
> +{
> + struct resource *req_mem_cc_regs = NULL;
> + struct cctrng_drvdata *drvdata;
> + struct device *dev = &pdev->dev;
> + int rc = 0;
> + u32 val;
> + int irq;
> +
> + drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> + if (!drvdata)
> + return -ENOMEM;
> +
> + drvdata->rng.name = devm_kstrdup(dev, dev_name(dev), GFP_KERNEL);
> + if (!drvdata->rng.name)
> + return -ENOMEM;
> +
> + drvdata->rng.read = cctrng_read;
> + drvdata->rng.priv = (unsigned long)drvdata;
> + drvdata->rng.quality = CC_TRNG_QUALITY;
> +
> + platform_set_drvdata(pdev, drvdata);
> + drvdata->pdev = pdev;
> +
> + drvdata->circ.buf = (char *)drvdata->data_buf;
> +
> + /* Get device resources */
> + /* First CC registers space */
> + req_mem_cc_regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + /* Map registers space */
> + drvdata->cc_base = devm_ioremap_resource(dev, req_mem_cc_regs);
> + if (IS_ERR(drvdata->cc_base)) {
> + dev_err(dev, "Failed to ioremap registers");
> + return PTR_ERR(drvdata->cc_base);
> + }
> +
> + dev_dbg(dev, "Got MEM resource (%s): %pR\n", req_mem_cc_regs->name,
> + req_mem_cc_regs);
> + dev_dbg(dev, "CC registers mapped from %pa to 0x%p\n",
> + &req_mem_cc_regs->start, drvdata->cc_base);
> +
> + /* Then IRQ */
> + irq = platform_get_irq(pdev, 0);
> + if (irq < 0) {
> + dev_err(dev, "Failed getting IRQ resource\n");
> + return irq;
> + }
> +
> + /* parse sampling rate from device tree */
> + rc = cc_trng_parse_sampling_ratio(drvdata);
> + if (rc) {
> + dev_err(dev, "Failed to get legal sampling ratio for rosc\n");
> + return rc;
> + }
> +
> + rc = cc_trng_clk_init(drvdata);
> + if (rc) {
> + dev_err(dev, "cc_trng_clk_init failed\n");
> + return rc;
> + }
> +
> + INIT_WORK(&drvdata->compwork, cc_trng_compwork_handler);
> + INIT_WORK(&drvdata->startwork, cc_trng_startwork_handler);
> + spin_lock_init(&drvdata->read_lock);
> +
> + /* register the driver isr function */
> + rc = devm_request_irq(dev, irq, cc_isr, IRQF_SHARED, "cctrng", drvdata);

Shoudn't this be done after clearing the pending interrupts below?

> + if (rc) {
> + dev_err(dev, "Could not register to interrupt %d\n", irq);
> + goto post_clk_err;
> + }
> + dev_dbg(dev, "Registered to IRQ: %d\n", irq);
> +
> + /* Clear all pending interrupts */
> + val = cc_ioread(drvdata, CC_HOST_RGF_IRR_REG_OFFSET);
> + dev_dbg(dev, "IRR=0x%08X\n", val);
> + cc_iowrite(drvdata, CC_HOST_RGF_ICR_REG_OFFSET, val);

The above accesses the engine's registers...

> +
> + /* unmask HOST RNG interrupt */
> + cc_iowrite(drvdata, CC_HOST_RGF_IMR_REG_OFFSET,
> + cc_ioread(drvdata, CC_HOST_RGF_IMR_REG_OFFSET) &
> + ~CC_HOST_RNG_IRQ_MASK);
> +
> + /* init PM */
> + rc = cc_trng_pm_init(drvdata);
> + if (rc) {
> + dev_err(dev, "cc_trng_pm_init failed\n");
> + goto post_clk_err;
> + }

> +
> + /* increment device's usage counter */
> + rc = cc_trng_pm_get(dev);

... but only here is Runtime PM initialized, and the device guaranteed
to be powered. If a device is accessed while powered down, this may
lead to an asynchronous external abort, or a plain lockup.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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