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Tue, 12 May 2020 04:49:13 -0500 Received: from DFLE113.ent.ti.com (10.64.6.34) by DFLE100.ent.ti.com (10.64.6.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1979.3; Tue, 12 May 2020 04:49:13 -0500 Received: from fllv0039.itg.ti.com (10.64.41.19) by DFLE113.ent.ti.com (10.64.6.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1979.3 via Frontend Transport; Tue, 12 May 2020 04:49:13 -0500 Received: from [10.250.234.195] (ileax41-snat.itg.ti.com [10.172.224.153]) by fllv0039.itg.ti.com (8.15.2/8.15.2) with ESMTP id 04C9n7cO076689; Tue, 12 May 2020 04:49:08 -0500 Subject: Re: [PATCH v4 00/16] mtd: spi-nor: add xSPI Octal DTR support To: , References: <20200424184410.8578-1-p.yadav@ti.com> <3649933.zuh8VGJVCz@192.168.0.120> <20200511112712.466f7246@collabora.com> <144878625.o7txgtY6sz@192.168.0.120> From: Vignesh Raghavendra Message-ID: <49abc8f3-5bb5-bc6d-b2ec-f14b115c58dc@ti.com> Date: Tue, 12 May 2020 15:19:07 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <144878625.o7txgtY6sz@192.168.0.120> Content-Language: en-US X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200512_024924_040398_1778FCFD X-CRM114-Status: GOOD ( 15.33 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alexandre.belloni@bootlin.com, richard@nod.at, nsekhar@ti.com, linux-kernel@vger.kernel.org, Nicolas.Ferre@microchip.com, Ludovic.Desroches@microchip.com, broonie@kernel.org, linux-mtd@lists.infradead.org, miquel.raynal@bootlin.com, linux-spi@vger.kernel.org, p.yadav@ti.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On 12/05/20 11:46 am, Tudor.Ambarus@microchip.com wrote: > Hi, Boris, Pratyush, > > I stripped case 2/, we'll not treat it for now. > > On Monday, May 11, 2020 12:27:12 PM EEST Boris Brezillon wrote: >> EXTERNAL EMAIL: Do not click links or open attachments unless you know the >> content is safe >> >> On Mon, 11 May 2020 09:00:35 +0000 >> >> wrote: >>> Hi, Pratyush, Boris, >>> >>> On Friday, April 24, 2020 9:43:54 PM EEST Pratyush Yadav wrote: >>>> This series adds support for octal DTR flashes in the spi-nor framework, >>> >>> I'm still learning about this, but I can give you my 2 cents as of now, to >>> open the discussion. Enabling 2-2-2, 4-4-4, and 8-8-8 modes is dangerous >>> because the flash may not recover from unexpected resets. Entering one of >>> these modes can be: >>> 1/ volatile selectable, the device return to the 1-1-1 protocol after the >>> next power-on. I guess this is conditioned by the optional RESET pin, but >>> I'll have to check. Also the flash can return to the 1-1-1 mode using the >>> software reset or through writing to its Configuration Register, without >>> power-on or power- off. >> >> My understanding is that there's no standard software reset procedure >> that guarantees no conflict with existing 1S commands, so even the >> software reset approach doesn't work here. >> > > The software reset procedure can't protect you from unexpected resets, but the > hardware with its optional reset pin can. Pratyush to confirm. > > cut > >> >>> Not recovering from unexpected resets is unacceptable. One should always >>> prefer option 1/ and condition the entering in 2-2-2, 4-4-4 and 8-8-8 with >>> the presence of the optional RESET pin. >> >> Totally agree with you on that one, but we know what happens in >> practice... > > What I proposed is to condition the entering in the state-full modes with the > presence of the optional RESET pin. We would introduce an optional device tree > property for the RESET pin. If hardware doesn't implement the optional RESET# > signal, then we will not enter in the state-full modes. > Are you asking for dedicated SW controllable reset line or just an indication from DT that OSPI reset line is connected to board level soft/hard reset lines? Mandating SW controllable RESET line is bit of a stretch IMO... Board design may not allow wasting dedicated pin due to lack of GPIOs perhaps.. For eg.: TI EVM has OSPI reset line connected to board level reset out. This ensures any soft/warm/hard CPU reset will trigger OSPI Flash reset, but there is no SW control that allows OSPI flash alone to be reset. Isn't such a reset mechanism sufficient? Regards Vignesh ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/