From: "Mahapatra, Amit Kumar" <amit.kumar-mahapatra@amd.com>
To: Mark Brown <broonie@kernel.org>
Cc: Amit Kumar Mahapatra <amit.kumar-mahapatra@xilinx.com>,
"p.yadav@ti.com" <p.yadav@ti.com>,
"miquel.raynal@bootlin.com" <miquel.raynal@bootlin.com>,
"richard@nod.at" <richard@nod.at>,
"vigneshr@ti.com" <vigneshr@ti.com>,
"git@xilinx.com" <git@xilinx.com>,
"michal.simek@xilinx.com" <michal.simek@xilinx.com>,
"linux-spi@vger.kernel.org" <linux-spi@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"michael@walle.cc" <michael@walle.cc>,
"linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
"git (AMD-Xilinx)" <git@amd.com>
Subject: RE: [RFC PATCH 1/2] spi: Add multiple CS support for a single SPI device
Date: Tue, 19 Jul 2022 13:21:41 +0000 [thread overview]
Message-ID: <BN7PR12MB280220006B18F06E9ADA31F5DC8F9@BN7PR12MB2802.namprd12.prod.outlook.com> (raw)
In-Reply-To: <YtGNnT2cP5HIayp3@sirena.org.uk>
Hello Mark,
> -----Original Message-----
> From: Mark Brown <broonie@kernel.org>
> Sent: Friday, July 15, 2022 9:24 PM
> To: Mahapatra, Amit Kumar <amit.kumar-mahapatra@amd.com>
> Cc: Amit Kumar Mahapatra <amit.kumar-mahapatra@xilinx.com>;
> 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) <git@amd.com>
> 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
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next prev parent reply other threads:[~2022-07-19 13:22 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-06 11:26 [RFC PATCH 0/2] spi: Add support for stacked/parallel memories Amit Kumar Mahapatra
2022-06-06 11:26 ` [RFC PATCH 1/2] spi: Add multiple CS support for a single SPI device Amit Kumar Mahapatra
2022-06-09 11:54 ` Mark Brown
2022-06-23 11:39 ` Mahapatra, Amit Kumar
2022-06-23 12:06 ` Mark Brown
2022-07-15 15:35 ` Mahapatra, Amit Kumar
2022-07-15 15:54 ` Mark Brown
2022-07-19 13:21 ` Mahapatra, Amit Kumar [this message]
2022-07-19 17:53 ` Mark Brown
2022-07-27 13:02 ` Mahapatra, Amit Kumar
2022-07-11 12:47 ` Michal Simek
2022-07-11 14:52 ` Mark Brown
2022-07-15 15:36 ` Mahapatra, Amit Kumar
2022-07-15 16:03 ` Mark Brown
2022-06-06 11:26 ` [RFC PATCH 2/2] mtd: spi-nor: Add support for stacked/parallel memories Amit Kumar Mahapatra
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