From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.bootlin.com ([62.4.15.54]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gHqNe-0005TC-BQ for linux-mtd@lists.infradead.org; Wed, 31 Oct 2018 13:17:56 +0000 Date: Wed, 31 Oct 2018 14:17:42 +0100 From: Boris Brezillon To: "Grandbois, Brett" Cc: Richard Weinberger , "linux-kernel@vger.kernel.org" , Marek Vasut , "linux-mtd@lists.infradead.org" , Brian Norris , David Woodhouse Subject: Re: [PATCH v2] mtd: spi-nor: Add support for SPI boot flash access for AMD Family 16h Message-ID: <20181031141742.4fd2d33b@bbrezillon> In-Reply-To: <1912426d-8189-0508-d152-8dfcf6192162@opengear.com> References: <20181016005726.26813-1-brett.grandbois@opengear.com> <20181027173945.241e87b2@bbrezillon> <20181030092605.38851906@bbrezillon> <1912426d-8189-0508-d152-8dfcf6192162@opengear.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 31 Oct 2018 03:18:28 +0000 "Grandbois, Brett" wrote: > On 30/10/18 6:26 pm, Boris Brezillon wrote: > > On Mon, 29 Oct 2018 23:15:42 +0000 > > "Grandbois, Brett" wrote: > > > >> On 28/10/18 1:39 am, Boris Brezillon wrote: > >>> Hi Brett, > >>> > >>> On Tue, 16 Oct 2018 00:57:41 +0000 > >>> "Grandbois, Brett" wrote: > >>> > >>>> Add support to expose the SPI boot flash on AMD Family 16h CPUs > >>>> as a standard mtd device to give userspace BIOS updaters greater > >>>> feature support. The BIOS and Kernel Developer's Guide refers to > >>>> this as the 'SPI ROM' controller and so the driver follows that > >>>> naming convention for consistency. > >>>> > >>> We're currently trying to convert spi-nor controller drivers to > >>> the spi-mem interface [1]. Can you look at this new interface and > >>> tell me if you'd be able to implement it? If that's not possible, > >>> then I'd prefer to have this driver implement the mtd_info > >>> interface directly. > >> So from going over the spi-mem interface it looks like the intent > >> is for these sorts of devices to be a standard spi_controller with > >> only mem_ops defined and the transfer/_one/_one_message left as > >> NULL? Is that correct? > > Yes > > > >> That's a bit of a pivot from how it's currently done > >> (it's conceptually similar to the intel-spi-pci driver so I was > >> following that) > > Yes, and that's exactly what I'd like to avoid. intel-spi-pci will > > probably be the trickiest conversion, so I'd like to avoid having > > another one ;-). > > > >> but I should be able to rework it to the new > >> interface. This then lives under drivers/spi and thus should be > >> submitted to linux-spi? > > Actually, if the controller is only ever connected to the same SPI > > NOR chip (no need for advanced detection scheme) and does not > > support support Octo/Quad/Dual modes (or any other advanced > > features), you'll be better off implementing > > mtd->_read/_write/_erase() directly (the driver would then live in > > drivers/mtd/devices/). > > Hmm, conceptually the device is better suited to the mtd layer than > the spi layer. The HW is designed to only ever access spi flash > chips, not as a general spi master controller, so really the end > result of it should always only ever be 1 mtd device. Unfortunately > as the device probing and command sequences for this are the same as > implemented in spi-nor I'd either be duplicating a lot of existing > code, or just wrapping around spi_nor_scan which sounds like we're > back to the dedicated spi-nor controller you're trying to move away > from. > > The spi-mem interface ops do nicely match up with what the controller > supports, including the new direct mapping mode which I'd be able to > make use of, so as long as there aren't any issues with supporting > only mem_ops and not the message transfers That's allowed. > then it's probably the way to go. Sounds good then.