From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean-Christophe PLAGNIOL-VILLARD Subject: Re: [PATCH 1/4 v5] of_spi: add generic binding support to specify cs gpio Date: Sun, 11 Mar 2012 19:25:37 +0100 Message-ID: <20120311182537.GS27213@game.jcrosoft.org> References: <1331122989-14451-1-git-send-email-plagnioj@jcrosoft.co> <1331317544-21735-1-git-send-email-plagnioj@jcrosoft.com> <20120311140731.2D4F93E0979@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20120311140731.2D4F93E0979@localhost> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Grant Likely Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: devicetree@vger.kernel.org On 08:07 Sun 11 Mar , Grant Likely wrote: > On Fri, 9 Mar 2012 19:25:44 +0100, Jean-Christophe PLAGNIOL-VILLARD wrote: > > This will allow to use gpio for chip select with no modification in the > > driver binding > > > > When use the cs-gpios, the gpio number will be passed via the cs_gpio field > > and the number of chip select will automatically increased. > > > > Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD > > Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org > > Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org > > --- > > v5: > > update grant comment to simplify the cs_gpio management > > > > Best Regards, > > J. > > Documentation/devicetree/bindings/spi/spi-bus.txt | 6 ++ > > drivers/spi/spi.c | 55 +++++++++++++++++++- > > include/linux/spi/spi.h | 4 ++ > > 3 files changed, 62 insertions(+), 3 deletions(-) > > > > diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt > > index e782add..c253379 100644 > > --- a/Documentation/devicetree/bindings/spi/spi-bus.txt > > +++ b/Documentation/devicetree/bindings/spi/spi-bus.txt > > @@ -12,6 +12,7 @@ The SPI master node requires the following properties: > > - #size-cells - should be zero. > > - compatible - name of SPI bus controller following generic names > > recommended practice. > > +- cs-gpios - (optional) gpios chip select. > > No other properties are required in the SPI bus node. It is assumed > > that a driver for an SPI bus device will understand that it is an SPI bus. > > However, the binding does not attempt to define the specific method for > > @@ -21,6 +22,8 @@ assumption that board specific platform code will be used to manage > > chip selects. Individual drivers can define additional properties to > > support describing the chip select layout. > > > > +If cs-gpios is used the number of chip select will automatically increased. > > + > > SPI slave nodes must be children of the SPI master node and can > > contain the following properties. > > - reg - (required) chip select address of device. > > @@ -34,6 +37,9 @@ contain the following properties. > > - spi-cs-high - (optional) Empty property indicating device requires > > chip select active high > > > > +If a gpio chipselect is used for the SPI slave the gpio number will be passed > > +via the cs_gpio > > + > > SPI example for an MPC5200 SPI bus: > > spi@f00 { > > #address-cells = <1>; > > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c > > index b2ccdea..446eee5 100644 > > --- a/drivers/spi/spi.c > > +++ b/drivers/spi/spi.c > > @@ -28,6 +28,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > > > @@ -322,6 +323,7 @@ struct spi_device *spi_alloc_device(struct spi_master *master) > > spi->dev.parent = &master->dev; > > spi->dev.bus = &spi_bus_type; > > spi->dev.release = spidev_release; > > + spi->cs_gpio = -EINVAL; > > device_initialize(&spi->dev); > > return spi; > > } > > @@ -339,15 +341,16 @@ EXPORT_SYMBOL_GPL(spi_alloc_device); > > int spi_add_device(struct spi_device *spi) > > { > > static DEFINE_MUTEX(spi_add_lock); > > - struct device *dev = spi->master->dev.parent; > > + struct spi_master *master = spi->master; > > + struct device *dev = master->dev.parent; > > struct device *d; > > int status; > > > > /* Chipselects are numbered 0..max; validate. */ > > - if (spi->chip_select >= spi->master->num_chipselect) { > > + if (spi->chip_select >= master->num_chipselect) { > > dev_err(dev, "cs%d >= max %d\n", > > spi->chip_select, > > - spi->master->num_chipselect); > > + master->num_chipselect); > > return -EINVAL; > > } > > > > @@ -371,6 +374,9 @@ int spi_add_device(struct spi_device *spi) > > goto done; > > } > > > > + if (master->cs_gpios) > > + spi->cs_gpio = master->cs_gpios[spi->chip_select]; > > + > > I still don't understand the need for this. Only the master driver will need > this data, and it is already stored in the master->cs_gpios array. Why > does it need to get duplicated into the spi_device? yeah can drop it > > > /* Drivers may modify this initial i/o setup, but will > > * normally rely on the device being setup. Devices > > * using SPI_CS_HIGH can't coexist well otherwise... > > @@ -561,6 +567,45 @@ struct spi_master *spi_alloc_master(struct device *dev, unsigned size) > > } > > EXPORT_SYMBOL_GPL(spi_alloc_master); > > > > +#ifdef CONFIG_OF > > +static int of_spi_register_master(struct spi_master *master) > > +{ > > + int nb, i; > > + int *cs; > > + struct device_node *np = master->dev.of_node; > > + > > + if (!np) > > + return 0; > > + > > + nb = of_gpio_named_count(np, "cs-gpios"); > > + > > + if (nb < 1) > > + return 0; > > + > > + cs = devm_kzalloc(&master->dev, > > + sizeof(int) * (master->num_chipselect + nb), > > + GFP_KERNEL); > > sizeof(*cs) > > > + master->cs_gpios = cs; > > + > > + if (!master->cs_gpios) > > + return -ENOMEM; > > + > > + memset(cs, -EINVAL, master->num_chipselect); > > + master->num_chipselect += nb; > > Looks buggy. Should be: > if (nb > master->num_chipselect) > master->num_chipselect = nb; > > However, this is actually quite risky. Changing the size of > num_chipselect without the driver knowing about it will most likely > cause breakage in drivers. Drivers may use it as an array index, and > if it gets increased then there will be problems. In fact, drivers > are probably using spi->chip_select as an array or register index so I > don't think it can be transparently extended to include gpios. > > So, this function must change. It cannot be called automatically > from spi_register_master(). It needs to be a library function that spi bus > drivers must call explicitly so they are prepared for a change in the > num_chipselect value. I'll prefer to let the spi framework manage it > > Also, if we're doing this, then the gpio cs manipulation hook should be > moved out of spi_bitbang and into the core spi_master. There should > also be a stock function for manipulating gpio chip selects. I don't want > spi driver authors under the impression that they should open code the > chip select manipulation. yeah I was thinking about it too how about we split it in two num_hw_cs manage by the drivers and num_gpio_cs for cs gpio and num_chipselect (hw + cs) will for internal use the gpio cs will be after the hw cs. and we move the gpio cs from spi_bitbang to spi_master Best Regards, J. > > + cs += master->num_chipselect; > > + > > + for (i = 0; i < nb; i++) > > + cs[i] = of_get_named_gpio(np, "cs-gpios", i); > > + > > + return 0; > > +} > > +#else > > +static int of_spi_register_master(struct spi_master *master) > > +{ > > + return 0; > > +} > > +#endif > > + > > /** > > * spi_register_master - register SPI master controller > > * @master: initialized master, originally from spi_alloc_master() > > @@ -592,6 +637,10 @@ int spi_register_master(struct spi_master *master) > > if (!dev) > > return -ENODEV; > > > > + status = of_spi_register_master(master); > > + if (status) > > + return status; > > + > > /* even if it's just one always-selected device, there must > > * be at least one chipselect > > */ > > diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h > > index 176fce9..328d492 100644 > > --- a/include/linux/spi/spi.h > > +++ b/include/linux/spi/spi.h > > @@ -89,6 +89,7 @@ struct spi_device { > > void *controller_state; > > void *controller_data; > > char modalias[SPI_NAME_SIZE]; > > + int cs_gpio; /* chip select gpio */ > > > > /* > > * likely need more hooks for more protocol options affecting how > > @@ -318,6 +319,9 @@ struct spi_master { > > > > /* called on release() to free memory provided by spi_master */ > > void (*cleanup)(struct spi_device *spi); > > + > > + /* gpio chip select */ > > + int *cs_gpios; > > }; > > > > static inline void *spi_master_get_devdata(struct spi_master *master) > > -- > > 1.7.7 > > > > _______________________________________________ > > devicetree-discuss mailing list > > devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org > > https://lists.ozlabs.org/listinfo/devicetree-discuss > > -- > Grant Likely, B.Sc, P.Eng. > Secret Lab Technologies,Ltd. ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/