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Received: from shell.armlinux.org.uk ([2001:4d48:ad52:3201:5054:ff:fe00:4ec]:49630) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jh8dR-0001kC-TS; Fri, 05 Jun 2020 10:27:34 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1jh8dC-0007LF-Q0; Fri, 05 Jun 2020 10:27:18 +0100 Date: Fri, 5 Jun 2020 10:27:18 +0100 From: Russell King - ARM Linux admin To: Neal Liu Subject: Re: Security Random Number Generator support Message-ID: <20200605092718.GH1551@shell.armlinux.org.uk> References: <1591085678-22764-1-git-send-email-neal.liu@mediatek.com> <85dfc0142d3879d50c0ba18bcc71e199@misterjones.org> <1591169342.4878.9.camel@mtkswgap22> <20200603093416.GY1551@shell.armlinux.org.uk> <1591341543.19510.4.camel@mtkswgap22> <20200605080905.GF1551@shell.armlinux.org.uk> <1591347582.21704.9.camel@mtkswgap22> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1591347582.21704.9.camel@mtkswgap22> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200605_022807_738268_4DDE41EC X-CRM114-Status: GOOD ( 21.17 ) X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Julius Werner , Herbert Xu , Arnd Bergmann , Marc Zyngier , Matt Mackall , Sean Wang , lkml , wsd_upstream , Rob Herring , "linux-mediatek@lists.infradead.org" , Linux Crypto Mailing List , Greg Kroah-Hartman , Matthias Brugger , Crystal Guo =?utf-8?B?KOmDreaZtik=?= , Ard Biesheuvel , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org On Fri, Jun 05, 2020 at 04:59:42PM +0800, Neal Liu wrote: > On Fri, 2020-06-05 at 09:09 +0100, Russell King - ARM Linux admin wrote: > > On Fri, Jun 05, 2020 at 03:19:03PM +0800, Neal Liu wrote: > > > On Wed, 2020-06-03 at 17:34 +0800, Russell King - ARM Linux admin wrote: > > > > This kind of thing is something that ARM have seems to shy away from > > > > doing - it's a point I brought up many years ago when the whole > > > > trustzone thing first appeared with its SMC call. Those around the > > > > conference table were not interested - ARM seemed to prefer every > > > > vendor to do off and do their own thing with the SMC interface. > > > > > > Does that mean it make sense to model a sec-rng driver, and get each > > > vendor's SMC function id by DT node? > > > > _If_ vendors have already gone off and decided to use different SMC > > function IDs for this, while keeping the rest of the SMC interface > > the same, then the choice has already been made. > > > > I know on 32-bit that some of the secure world implementations can't > > be changed; they're burnt into the ROM. I believe on 64-bit that isn't > > the case, which makes it easier to standardise. > > > > Do you have visibility of how this SMC is implemented in the secure > > side? Is it in ATF, and is it done as a vendor hack or is there an > > element of generic implementation to it? Has it been submitted > > upstream to the main ATF repository? > > > > Take MediaTek as an example, some SoCs are implemented in ATF, some of > them are implemented in TEE. We have no plan to make generic > implementation in "secure world". I think you have your answer right there - by _not_ making the API generic and giving no motivation to use it, different vendors are going to do different things (maybe even with a different API as well) so there's no point the kernel driver pretending to be a generic driver. If the driver isn't going to be generic, I see little point in the SMC function number being in DT. I think that as a _whole_ is a big mistake - there should be a generic kernel driver for this, and there should be a standardised interface to it through firmware. So, I would encourage you to try to get it accepted one way or another amongst vendors as a standardised interface. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC for 0.8m (est. 1762m) line in suburbia: sync at 13.1Mbps down 424kbps up _______________________________________________ Linux-mediatek mailing list Linux-mediatek@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek