linux-kernel - Re: [PATCH v3 6/6] crypto: qcom: Add ACPI support

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Message-ID: <20180704041154.GU22377@vkoul-mobl>
Date:   Wed, 4 Jul 2018 09:41:54 +0530
From:   Vinod <vkoul@...nel.org>
To:     Timur Tabi <timur@...nel.org>
Cc:     linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Matt Mackall <mpm@...enic.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-msm@...r.kernel.org, Stephen Boyd <swboyd@...omium.org>,
        Jeffrey Hugo <jhugo@...eaurora.org>
Subject: Re: [PATCH v3 6/6] crypto: qcom: Add ACPI support

On 03-07-18, 09:10, Timur Tabi wrote:
> On 7/3/18 1:04 AM, Vinod Koul wrote:
> > Add support for probing on ACPI systems, with ACPI HID QCOM8160.
> > 
> > On ACPI systems, clocks are always enabled, the PRNG should
> > already be enabled, and the register region is read-only.
> > The driver only verifies that the hardware is already
> > enabled never tries to disable or configure it.
> > 
> > Signed-off-by: Timur Tabi<timur@...eaurora.org>
> > [port to crypto API]
> > Signed-off-by: Vinod Koul<vkoul@...nel.org>
> 
> I've asked a colleague who still works at Qualcomm to test this code on
> silicon.  It looks okay, but I just want to be sure.
> 
> > +	/*
> > +	 * ACPI systems have v2 hardware. The clocks are always enabled,
> > +	 * the PRNG register space is read-only and the PRNG should
> > +	 * already be enabled.
> > +	 */
> > +	if (has_acpi_companion(&pdev->dev)) {
> > +		val = readl(rng->base + PRNG_CONFIG);
> > +		if (!(val & PRNG_CONFIG_HW_ENABLE)) {
> > +			dev_err(&pdev->dev, "device is not enabled\n");
> > +			return -ENODEV;
> > +		}
> 
> I'm having second thoughts about this PRNG_CONFIG_HW_ENABLE check.  The PRNG
> on the QDF2400 is the same as the one on the 8996, so it should have the
> same register interface.  Currently, the ACPI table points to a full PRNG
> register block, but I'm beginning to believe that it should instead point to
> a "reduced" block that doesn't have a PRNG_CONFIG register.

That was my doubt too. I will go ahead and make it skip this then...

-- 
~Vinod