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 1fSRT4-0004HJ-O3 for linux-mtd@lists.infradead.org; Mon, 11 Jun 2018 18:23:14 +0000 Date: Mon, 11 Jun 2018 20:22:49 +0200 From: Boris Brezillon To: Ladislav Michl Cc: linux-mtd@lists.infradead.org, Alexandre Belloni , Nicolas Ferre Subject: Re: atmel-nand-controller: NAND chip selects? Message-ID: <20180611202249.63a11950@bbrezillon> In-Reply-To: <20180611144214.GA19449@lenoch> References: <20180611110425.GA4059@lenoch> <20180611132131.4f175aea@bbrezillon> <20180611144214.GA19449@lenoch> 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 Mon, 11 Jun 2018 16:42:14 +0200 Ladislav Michl wrote: > On Mon, Jun 11, 2018 at 01:21:31PM +0200, Boris Brezillon wrote: > > On Mon, 11 Jun 2018 13:04:25 +0200 > > Ladislav Michl wrote: > > > > > Consider there are more NAND chips connected to the same lines and only nCE > > > (connected to GPIO line one per each chip) is used to select them. > > > How is driver supposed to work in such situation? > > > Common memory region cannot be requested multiple times as well as the > > > same gpio for R/B cannot be requested. > > > > I thought you could request several times the same GPIO if it's in input > > mode, but maybe I'm wrong. > > Well, it does not seem to work: > atmel-nand-controller 10000000.ebi:nand-controller: Failed to get R/B gpio (err = -16) Okay, that's a problem. > > > > Something as davinci_nand for > > > memory region? Use 'ranges' property? How should one express in DT gpio > > > is shared between child nodes? > > > > For both problems, the solution is to reserve the resources at the NAND > > controller level instead of the NAND level. It's pretty easy for the CS > > memory range, because the driver can easily detect when the same CS is > > used by different NAND chips. It's a bit more complicated for the R/B > > pins. > > Do you mean something like this? > > ebi: ebi@10000000 { > status = "okay"; > pinctrl-0 = <&pinctrl_nand_cs &pinctrl_nand_cs1 &pinctrl_nand_rb>; > pinctrl-names = "default"; > > nand_controller: nand-controller { > status = "okay"; > /* reg = <0x3 0x0 0x800000>; */ > nand@3,0 { > reg = <0x3 0x0 0x800000>; > rb-gpios = <&pioC 13 GPIO_ACTIVE_HIGH>; > cs-gpios = <&pioC 8 GPIO_ACTIVE_HIGH>; > nand-bus-width = <8>; > nand-ecc-mode = "soft"; > nand-ecc-algo = "bch"; > nand-ecc-strength = <8>; > nand-on-flash-bbt; > label = "atmel_nand"; > }; > nand@3,1 { > reg = <0x3 0x0 0x800000>; > rb-gpios = <&pioC 13 GPIO_ACTIVE_HIGH>; > cs-gpios = <&pioC 14 GPIO_ACTIVE_HIGH>; > nand-bus-width = <8>; > nand-ecc-mode = "soft"; > nand-ecc-algo = "bch"; > nand-ecc-strength = <8>; > nand-on-flash-bbt; > label = "atmel_nand"; Two devices with the same label, that probably won't work correctly. > }; > }; > }; > > Note the commented out 'reg' property. I'm not sure if you meant to actively > compare 'reg's of nand child nodes or put 'reg' property on 'nand-controller' I thought about doing the former. The first cell in reg is encoding the EBI CS, so it's pretty easy to have a table of already requested CS ids in struct atmel_nand_controller, and when you see the same CS, you just have to get the already requested iomem region. > level (latter does not currently fly): > atmel-ebi 10000000.ebi: missing or invalid timings definition in /ahb/ebi@10000000/nand-controller > atmel-ebi 10000000.ebi: failed to configure EBI bus for /ahb/ebi@10000000/nand-controller, disabling the device It's caused by this check [1] because I assumed the NAND controller would never have a reg prop defined. If we need to, we can extend the check to make sure the child not does not have an "atmel,xxx-nand-controller" compat. [1]https://elixir.bootlin.com/linux/v4.17/source/drivers/memory/atmel-ebi.c#L573 [2]https://elixir.bootlin.com/linux/v4.17/source/drivers/mtd/nand/raw/atmel/nand-controller.c#L2435