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

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Date:   Tue, 3 Jul 2018 09:10:06 -0500
From:   Timur Tabi <timur@...nel.org>
To:     Vinod Koul <vkoul@...nel.org>, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     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 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.