From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pali =?utf-8?B?Um9ow6Fy?= Subject: Re: [RFC] ARM: omap3: Enable HWMODS for HW Random Number Generator Date: Tue, 10 Sep 2019 16:44:52 +0200 Message-ID: <20190910144452.vmhmls3xhh6hd5xw@pali> References: <20190828150037.2640-1-aford173@gmail.com> <20190905230443.GA52127@atomide.com> <20190910143732.3g3q4acvnx2pqvjx@earth.universe> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <20190910143732.3g3q4acvnx2pqvjx@earth.universe> Sender: linux-kernel-owner@vger.kernel.org To: Sebastian Reichel Cc: Adam Ford , Tony Lindgren , Mark Rutland , devicetree , Paul Walmsley , Aaro Koskinen , Russell King , Linux Kernel Mailing List , Tero Kristo , Rob Herring , =?utf-8?Q?Beno=C3=AEt?= Cousson , Linux-OMAP , Adam Ford , arm-soc List-Id: devicetree@vger.kernel.org On Tuesday 10 September 2019 15:37:32 Sebastian Reichel wrote: > Hi, > > On Tue, Sep 10, 2019 at 08:56:49AM -0500, Adam Ford wrote: > > On Thu, Sep 5, 2019 at 6:04 PM Tony Lindgren wrote: > > > Oh and this needs to default to status = "disabled" for > > > HS devices like n900 as it needs to use the omap3-rom-rng. > > > > I don't know enough about the HS version of the OMAP3, but what's the > > main difference between omap3-rom-rng and this one? > > The OMAP HS chips have the bus firewall configured to block direct > access to some cryptography related devices. The kernel will crash > with a bus error, if you try to read/write the registers for > protected devices. And if you try to read it more times, SOC would be rebooted for security reasons. > The omap3-rom-rng avoids this by communicating > with the security middleware component instead of directly accessing > the RNG hardware. And that component is loaded by signed bootloader into "secure" area not accessible by "non-secure" work (like kernel) and communication is done via arm smc instruction. -- Pali Rohár pali.rohar@gmail.com