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Tue, 19 Jul 2022 13:21:42 +0000 Received: from BN7PR12MB2802.namprd12.prod.outlook.com ([fe80::30c4:f356:a806:509a]) by BN7PR12MB2802.namprd12.prod.outlook.com ([fe80::30c4:f356:a806:509a%7]) with mapi id 15.20.5438.023; Tue, 19 Jul 2022 13:21:42 +0000 From: "Mahapatra, Amit Kumar" To: Mark Brown CC: Amit Kumar Mahapatra , "p.yadav@ti.com" , "miquel.raynal@bootlin.com" , "richard@nod.at" , "vigneshr@ti.com" , "git@xilinx.com" , "michal.simek@xilinx.com" , "linux-spi@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "michael@walle.cc" , "linux-mtd@lists.infradead.org" , "git (AMD-Xilinx)" Subject: RE: [RFC PATCH 1/2] spi: Add multiple CS support for a single SPI device Thread-Topic: [RFC PATCH 1/2] spi: Add multiple CS support for a single SPI device Thread-Index: AQHYeZhXApErq+32kkmuJFVVfXogSAG7F8aMAeAoVR+snXQgIICishAAgCJ4JhCAAFqwgIAF7C1A Date: Tue, 19 Jul 2022 13:21:41 +0000 Message-ID: References: <20220606112607.20800-1-amit.kumar-mahapatra@xilinx.com> <20220606112607.20800-2-amit.kumar-mahapatra@xilinx.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org Hello Mark, > -----Original Message----- > From: Mark Brown > Sent: Friday, July 15, 2022 9:24 PM > To: Mahapatra, Amit Kumar > Cc: Amit Kumar Mahapatra ; > p.yadav@ti.com; miquel.raynal@bootlin.com; richard@nod.at; > vigneshr@ti.com; git@xilinx.com; michal.simek@xilinx.com; linux- > spi@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux- > kernel@vger.kernel.org; michael@walle.cc; linux-mtd@lists.infradead.org; > git (AMD-Xilinx) > Subject: Re: [RFC PATCH 1/2] spi: Add multiple CS support for a single SPI > device > > On Fri, Jul 15, 2022 at 03:35:49PM +0000, Mahapatra, Amit Kumar wrote: > > > > That doesn't address the issue, the issue is checking that the > > > driver can support multiple chip selects. > > > To address this issue, in spi core we will check the number of items > > in the "reg" property of the flash node(which is nothing but the > > number of chip selects) against the "num-cs" property of the spi > > controller(which is total number of chip selects supported by the > > controller). If the number of items mentioned in the "reg" property is > > greater than "num-cs" value then we error out. > > > For eg., > > > rc = of_property_read_variable_u32_array(nc, "reg", &cs[0], 1, > > SPI_CS_CNT_MAX); > > if(rc > ctlr->num_chipselect) { > > dev_err(&ctlr->dev, "%pOF has invalid 'reg' property (%d)\n", > > nc, rc); > > return -EINVAL; > > } > > This would check that the controller has at least the number of chip selects > specified but it would not check that the controller is actually capable of > using more than one chip select at once. We should be validating both that I agree, so for checking the controller multiple chip select capability(using more than one chip select at once) we can define a new spi controller DT property like "multi-cs-cap"(please suggest a better name). The controller that can support multiple chip selects should have this property in the spi controller DT node. The spi core will check ctlr->multi-cs-cap to operate multiple chip select in parallel. > the chip selects are available and that the controller can do something useful > with them (and probably have an implementation in the core for doing so via > GPIO). Here are you referring to the usecase in which a controller implementing multi CS support using GPIO? Regards, Amit ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/