linux-crypto.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Hadar Gat <Hadar.Gat@arm.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Matt Mackall <mpm@selenic.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <Mark.Rutland@arm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Alexander Sverdlin <alexander.sverdlin@nokia.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Tomer Maimon <tmaimon77@gmail.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Zaibo Xu <xuzaibo@huawei.com>,
	Daniel Thompson <daniel.thompson@linaro.org>,
	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Gilad Ben-Yossef <gilad@benyossef.com>,
	Ofir Drang <Ofir.Drang@arm.com>, nd <nd@arm.com>
Subject: RE: [PATCH v7 2/3] hw_random: cctrng: introduce Arm CryptoCell driver
Date: Tue, 21 Apr 2020 13:16:16 +0000	[thread overview]
Message-ID: <DB6PR0802MB25338BD19DD2F7E662BB1065E9D50@DB6PR0802MB2533.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <CAMuHMdV6Uce79MPs7jfJfX3WOqAMH22vf2V_=Ui0zLHYqsJ+Xg@mail.gmail.com>

Thank you Geert for reviewing the cctrng code.

> -----Original Message-----
> From: Geert Uytterhoeven <geert@linux-m68k.org>
> Sent: Monday, 20 April 2020 16:45
> 
> 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?

I'm not sure what do you mean in your question...
I assume you're suggesting that the registration of the driver ISR function should be done only after clearing the pending interrupts?!
Anyway, any pending interrupt that might exist is irrelevant to the current cctrng driver which just started (we're in the probe function)

> > +       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...

That is right.

> > +
> > +       /* 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.

It is assumed that when the driver is probed it is already powered. Only then, the driver initializes and enables the runtime PM to allow power down of the HW when it is not in use.

> 
> 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

  reply	other threads:[~2020-04-21 13:16 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-27  6:10 [PATCH v7 0/3] hw_random: introduce Arm CryptoCell TRNG driver Hadar Gat
2020-03-27  6:10 ` [PATCH v7 1/3] dt-bindings: add device tree binding for Arm CryptoCell trng engine Hadar Gat
2020-04-05  1:30   ` Rob Herring
2020-03-27  6:10 ` [PATCH v7 2/3] hw_random: cctrng: introduce Arm CryptoCell driver Hadar Gat
2020-04-20 13:44   ` Geert Uytterhoeven
2020-04-21 13:16     ` Hadar Gat [this message]
2020-04-21 13:34       ` Geert Uytterhoeven
2020-04-21 15:13         ` Hadar Gat
2020-04-21 16:26           ` Geert Uytterhoeven
2020-04-22 10:37             ` Hadar Gat
2020-03-27  6:10 ` [PATCH v7 3/3] MAINTAINERS: add HG as cctrng maintainer Hadar Gat
2020-04-16  6:51 ` [PATCH v7 0/3] hw_random: introduce Arm CryptoCell TRNG driver Herbert Xu
2020-04-20  9:34 ` Geert Uytterhoeven
2020-04-20 12:27   ` Hadar Gat
2020-04-20 13:45     ` Geert Uytterhoeven
2020-04-21 13:12       ` Hadar Gat
2020-04-21 13:39         ` Geert Uytterhoeven

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=DB6PR0802MB25338BD19DD2F7E662BB1065E9D50@DB6PR0802MB2533.eurprd08.prod.outlook.com \
    --to=hadar.gat@arm.com \
    --cc=Jonathan.Cameron@huawei.com \
    --cc=Mark.Rutland@arm.com \
    --cc=Ofir.Drang@arm.com \
    --cc=alexander.sverdlin@nokia.com \
    --cc=arnd@arndb.de \
    --cc=daniel.thompson@linaro.org \
    --cc=davem@davemloft.net \
    --cc=devicetree@vger.kernel.org \
    --cc=f.fainelli@gmail.com \
    --cc=geert@linux-m68k.org \
    --cc=gilad@benyossef.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=herbert@gondor.apana.org.au \
    --cc=krzk@kernel.org \
    --cc=linux-crypto@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mchehab+samsung@kernel.org \
    --cc=mpm@selenic.com \
    --cc=nd@arm.com \
    --cc=rdunlap@infradead.org \
    --cc=robh+dt@kernel.org \
    --cc=tglx@linutronix.de \
    --cc=tmaimon77@gmail.com \
    --cc=xuzaibo@huawei.com \
    --subject='RE: [PATCH v7 2/3] hw_random: cctrng: introduce Arm CryptoCell driver' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).