Message-ID: <BN7PR12MB28026E2EBD64F0D49A1084ABDCBBA@BN7PR12MB2802.namprd12.prod.outlook.com>
Date:   Tue, 21 Nov 2023 07:39:06 +0000
From:   "Mahapatra, Amit Kumar" <amit.kumar-mahapatra@....com>
To:     Stefan Binding <sbinding@...nsource.cirrus.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "tudor.ambarus@...aro.org" <tudor.ambarus@...aro.org>,
        "pratyush@...nel.org" <pratyush@...nel.org>,
        "miquel.raynal@...tlin.com" <miquel.raynal@...tlin.com>,
        "richard@....at" <richard@....at>,
        "vigneshr@...com" <vigneshr@...com>
CC:     "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "michael@...le.cc" <michael@...le.cc>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        "claudiu.beznea@...on.dev" <claudiu.beznea@...on.dev>,
        "Simek, Michal" <michal.simek@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "git (AMD-Xilinx)" <git@....com>,
        "amitrkcian2002@...il.com" <amitrkcian2002@...il.com>,
        "patches@...nsource.cirrus.com" <patches@...nsource.cirrus.com>
Subject: RE: [PATCH v10 1/8] spi: Add multi-cs memories support in SPI core

Hello Stefan,

> -----Original Message-----
> From: Stefan Binding <sbinding@...nsource.cirrus.com>
> Sent: Monday, November 20, 2023 8:00 PM
> To: Mahapatra, Amit Kumar <amit.kumar-mahapatra@....com>;
> broonie@...nel.org; tudor.ambarus@...aro.org; pratyush@...nel.org;
> miquel.raynal@...tlin.com; richard@....at; vigneshr@...com
> Cc: linux-spi@...r.kernel.org; linux-kernel@...r.kernel.org;
> michael@...le.cc; linux-mtd@...ts.infradead.org;
> nicolas.ferre@...rochip.com; alexandre.belloni@...tlin.com;
> claudiu.beznea@...on.dev; Simek, Michal <michal.simek@....com>; linux-
> arm-kernel@...ts.infradead.org; git (AMD-Xilinx) <git@....com>;
> amitrkcian2002@...il.com; patches@...nsource.cirrus.com
> Subject: Re: [PATCH v10 1/8] spi: Add multi-cs memories support in SPI core
> 
> 
> On 18/11/2023 13:54, Amit Kumar Mahapatra wrote:
> > AMD-Xilinx GQSPI controller has two advanced mode that allows the
> > controller to consider two flashes as one single device.
> >
> > One of these two mode is the parallel mode in which each byte of data
> > is stored in both devices, the even bits in the lower flash & the odd
> > bits in the upper flash. The byte split is automatically handled by
> > the QSPI controller.
> >
> > The other mode is the stacked mode in which both the flashes share the
> > same SPI bus but each of the device contain half of the data. In this
> > mode, the controller does not follow CS requests but instead
> > internally wires the two CS levels with the value of the most significant
> address bit.
> >
> > For supporting both these modes SPI core need to be updated for
> > providing multiple CS for a single SPI device.
> >
> > For adding multi CS support the SPI device need to be aware of all the
> > CS values. So, the "chip_select" member in the spi_device structure is
> > now an array that holds all the CS values.
> >
> > spi_device structure now has a "cs_index_mask" member. This acts as an
> > index to the chip_select array. If nth bit of spi->cs_index_mask is
> > set then the driver would assert spi->chip_select[n].
> >
> > In parallel mode all the chip selects are asserted/de-asserted
> > simultaneously and each byte of data is stored in both devices, the
> > even bits in one, the odd bits in the other. The split is
> > automatically handled by the GQSPI controller. The GQSPI controller
> > supports a maximum of two flashes connected in parallel mode. A
> > SPI_CONTROLLER_MULTI_CS flag bit is added in the spi controller flags,
> > through ctlr->flags the spi core will make sure that the controller is
> > capable of handling multiple chip selects at once.
> >
> > For supporting multiple CS via GPIO the cs_gpiod member of the
> > spi_device structure is now an array that holds the gpio descriptor
> > for each chipselect.
> >
> > CS GPIO is not tested due to unavailability of necessary hardware setup.
> >
> > Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>
> > ---
> > Hello @Stefen,
> > We restructured the SPI core implementation, for handling arbitrary
> > number of devices connected in parallel(multi-cs) or stacked mode. We
> > have tested this updated patch on native-cs setup but couldn't test
> > cs-gpio due to unavailability of a proper setup. If possible,  could
> > you please retest the cs-gpio use case with this updated patch and provide
> your feedback.
> 
> Hi,
> 
> I tested this chain on 2 different systems using GPIOs as chip selects, and see
> the same error on both:
> [    2.842045] pxa2xx-spi pxa2xx-spi.6: chipselect 0 already in use
> 
> Let me know if you need any further testing.
> 
> Thanks,
> 
> Stefan Binding
> 
> > ---
> >   drivers/spi/spi.c       | 192 +++++++++++++++++++++++++++++++---------
> >   include/linux/spi/spi.h |  51 ++++++++---
> >   2 files changed, 191 insertions(+), 52 deletions(-)
> >
> > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index
> > 8ead7acb99f3..ff66147ba95f 100644
> > --- a/drivers/spi/spi.c
> > +++ b/drivers/spi/spi.c
> > @@ -612,10 +612,21 @@ static int spi_dev_check(struct device *dev, void
> *data)
> >   {
> >   	struct spi_device *spi = to_spi_device(dev);
> >   	struct spi_device *new_spi = data;
> > -
> > -	if (spi->controller == new_spi->controller &&
> > -	    spi_get_chipselect(spi, 0) == spi_get_chipselect(new_spi, 0))
> > -		return -EBUSY;
> > +	int idx, nw_idx;
> > +	u8 cs, cs_nw;
> > +
> > +	if (spi->controller == new_spi->controller) {
> > +		for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> > +			cs = spi_get_chipselect(spi, idx);
> > +			for (nw_idx = 0; nw_idx < SPI_CS_CNT_MAX;
> nw_idx++) {
> > +				cs_nw = spi_get_chipselect(spi, nw_idx);

Thank you for dedicating your time to test my patch.
As per my analysis the error is reported from here as we are 
supplying the former SPI device structure to retrieve the CS 
value for the new SPI devices.
To fix this, could you kindly substitute the above line with 

cs_nw = spi_get_chipselect(new_spi, nw_idx);

and rerun your tests? 
If it works correctly, I will incorporate this fix into my 
upcoming series.

Regards,
Amit

> > +				if (cs != 0xFF && cs_nw != 0xFF && cs ==
> cs_nw) {
> > +					dev_err(dev, "chipselect %d already in
> use\n", cs_nw);
> > +					return -EBUSY;
> > +				}
> > +			}
> > +		}
> > +	}
> >   	return 0;
> >   }
> >
> > @@ -629,13 +640,32 @@ static int __spi_add_device(struct spi_device *spi)
> >   {
> >   	struct spi_controller *ctlr = spi->controller;
> >   	struct device *dev = ctlr->dev.parent;
> > -	int status;
> > +	int status, idx, nw_idx;
> > +	u8 cs, nw_cs;
> > +
> > +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> > +		/* Chipselects are numbered 0..max; validate. */
> > +		cs = spi_get_chipselect(spi, idx);
> > +		if (cs != 0xFF && cs >= ctlr->num_chipselect) {
> > +			dev_err(dev, "cs%d >= max %d\n",
> spi_get_chipselect(spi, idx),
> > +				ctlr->num_chipselect);
> > +			return -EINVAL;
> > +		}
> > +	}
> >
> > -	/* Chipselects are numbered 0..max; validate. */
> > -	if (spi_get_chipselect(spi, 0) >= ctlr->num_chipselect) {
> > -		dev_err(dev, "cs%d >= max %d\n", spi_get_chipselect(spi, 0),
> > -			ctlr->num_chipselect);
> > -		return -EINVAL;
> > +	/*
> > +	 * Make sure that multiple logical CS doesn't map to the same
> physical CS.
> > +	 * For example, spi->chip_select[0] != spi->chip_select[1] and so on.
> > +	 */
> > +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> > +		cs = spi_get_chipselect(spi, idx);
> > +		for (nw_idx = idx + 1; nw_idx < SPI_CS_CNT_MAX; nw_idx++) {
> > +			nw_cs = spi_get_chipselect(spi, nw_idx);
> > +			if (cs != 0xFF && nw_cs != 0xFF && cs == nw_cs) {
> > +				dev_err(dev, "chipselect %d already in use\n",
> nw_cs);
> > +				return -EBUSY;
> > +			}
> > +		}
> >   	}
> >
> >   	/* Set the bus ID string */
> > @@ -647,11 +677,8 @@ static int __spi_add_device(struct spi_device *spi)
> >   	 * its configuration.
> >   	 */
> >   	status = bus_for_each_dev(&spi_bus_type, NULL, spi, spi_dev_check);
> > -	if (status) {
> > -		dev_err(dev, "chipselect %d already in use\n",
> > -				spi_get_chipselect(spi, 0));
> > +	if (status)
> >   		return status;
> > -	}
> >
> >   	/* Controller may unregister concurrently */
> >   	if (IS_ENABLED(CONFIG_SPI_DYNAMIC) && @@ -659,8 +686,15 @@
> static
> > int __spi_add_device(struct spi_device *spi)
> >   		return -ENODEV;
> >   	}
> >
> > -	if (ctlr->cs_gpiods)
> > -		spi_set_csgpiod(spi, 0, ctlr->cs_gpiods[spi_get_chipselect(spi,
> 0)]);
> > +	if (ctlr->cs_gpiods) {
> > +		u8 cs;
> > +
> > +		for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> > +			cs = spi_get_chipselect(spi, idx);
> > +			if (cs != 0xFF)
> > +				spi_set_csgpiod(spi, idx, ctlr->cs_gpiods[cs]);
> > +		}
> > +	}
> >
> >   	/*
> >   	 * Drivers may modify this initial i/o setup, but will @@ -701,6
> > +735,9 @@ int spi_add_device(struct spi_device *spi)
> >   	struct spi_controller *ctlr = spi->controller;
> >   	int status;
> >
> > +	/* Set the bus ID string */
> > +	spi_dev_set_name(spi);
> > +
> >   	mutex_lock(&ctlr->add_lock);
> >   	status = __spi_add_device(spi);
> >   	mutex_unlock(&ctlr->add_lock);
> > @@ -942,32 +979,51 @@ static void spi_res_release(struct spi_controller
> *ctlr, struct spi_message *mes
> >   }
> >
> >
> > /*--------------------------------------------------------------------
> > -----*/
> > +static inline bool spi_is_last_cs(struct spi_device *spi) {
> > +	u8 idx;
> > +	bool last = false;
> > +
> > +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> > +		if ((spi->cs_index_mask >> idx) & 0x01) {
> > +			if (spi->controller->last_cs[idx] ==
> spi_get_chipselect(spi, idx))
> > +				last = true;
> > +		}
> > +	}
> > +	return last;
> > +}
> > +
> >
> >   static void spi_set_cs(struct spi_device *spi, bool enable, bool force)
> >   {
> >   	bool activate = enable;
> > +	u8 idx;
> >
> >   	/*
> >   	 * Avoid calling into the driver (or doing delays) if the chip select
> >   	 * isn't actually changing from the last time this was called.
> >   	 */
> > -	if (!force && ((enable && spi->controller->last_cs ==
> spi_get_chipselect(spi, 0)) ||
> > -		       (!enable && spi->controller->last_cs !=
> spi_get_chipselect(spi, 0))) &&
> > +	if (!force && ((enable && spi->controller->last_cs_index_mask == spi-
> >cs_index_mask &&
> > +			spi_is_last_cs(spi)) ||
> > +		       (!enable && spi->controller->last_cs_index_mask == spi-
> >cs_index_mask &&
> > +			!spi_is_last_cs(spi))) &&
> >   	    (spi->controller->last_cs_mode_high == (spi->mode &
> SPI_CS_HIGH)))
> >   		return;
> >
> >   	trace_spi_set_cs(spi, activate);
> >
> > -	spi->controller->last_cs = enable ? spi_get_chipselect(spi, 0) : -1;
> > +	spi->controller->last_cs_index_mask = spi->cs_index_mask;
> > +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++)
> > +		spi->controller->last_cs[idx] = enable ? spi_get_chipselect(spi,
> 0)
> > +: -1;
> >   	spi->controller->last_cs_mode_high = spi->mode & SPI_CS_HIGH;
> >
> > -	if ((spi_get_csgpiod(spi, 0) || !spi->controller->set_cs_timing) &&
> !activate)
> > -		spi_delay_exec(&spi->cs_hold, NULL);
> > -
> >   	if (spi->mode & SPI_CS_HIGH)
> >   		enable = !enable;
> >
> > -	if (spi_get_csgpiod(spi, 0)) {
> > +	if (spi_is_csgpiod(spi)) {
> > +		if (!spi->controller->set_cs_timing && !activate)
> > +			spi_delay_exec(&spi->cs_hold, NULL);
> > +
> >   		if (!(spi->mode & SPI_NO_CS)) {
> >   			/*
> >   			 * Historically ACPI has no means of the GPIO polarity
> and @@
> > -979,26 +1035,38 @@ static void spi_set_cs(struct spi_device *spi, bool
> enable, bool force)
> >   			 * ambiguity. That's why we use enable, that takes
> SPI_CS_HIGH
> >   			 * into account.
> >   			 */
> > -			if (has_acpi_companion(&spi->dev))
> > -
> 	gpiod_set_value_cansleep(spi_get_csgpiod(spi, 0), !enable);
> > -			else
> > -				/* Polarity handled by GPIO library */
> > -
> 	gpiod_set_value_cansleep(spi_get_csgpiod(spi, 0), activate);
> > +			for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> > +				if (((spi->cs_index_mask >> idx) & 0x01) &&
> > +				    spi_get_csgpiod(spi, idx)) {
> > +					if (has_acpi_companion(&spi->dev))
> > +
> 	gpiod_set_value_cansleep(spi_get_csgpiod(spi, idx),
> > +
> !enable);
> > +					else
> > +						/* Polarity handled by GPIO
> library */
> > +
> 	gpiod_set_value_cansleep(spi_get_csgpiod(spi, idx),
> > +
> activate);
> > +
> > +					if (activate)
> > +						spi_delay_exec(&spi-
> >cs_setup, NULL);
> > +					else
> > +						spi_delay_exec(&spi-
> >cs_inactive, NULL);
> > +				}
> > +			}
> >   		}
> >   		/* Some SPI masters need both GPIO CS & slave_select */
> >   		if ((spi->controller->flags & SPI_CONTROLLER_GPIO_SS) &&
> >   		    spi->controller->set_cs)
> >   			spi->controller->set_cs(spi, !enable);
> > +
> > +		if (!spi->controller->set_cs_timing) {
> > +			if (activate)
> > +				spi_delay_exec(&spi->cs_setup, NULL);
> > +			else
> > +				spi_delay_exec(&spi->cs_inactive, NULL);
> > +		}
> >   	} else if (spi->controller->set_cs) {
> >   		spi->controller->set_cs(spi, !enable);
> >   	}
> > -
> > -	if (spi_get_csgpiod(spi, 0) || !spi->controller->set_cs_timing) {
> > -		if (activate)
> > -			spi_delay_exec(&spi->cs_setup, NULL);
> > -		else
> > -			spi_delay_exec(&spi->cs_inactive, NULL);
> > -	}
> >   }
> >
> >   #ifdef CONFIG_HAS_DMA
> > @@ -2222,8 +2290,8 @@ static void of_spi_parse_dt_cs_delay(struct
> device_node *nc,
> >   static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
> >   			   struct device_node *nc)
> >   {
> > -	u32 value;
> > -	int rc;
> > +	u32 value, cs[SPI_CS_CNT_MAX];
> > +	int rc, idx;
> >
> >   	/* Mode (clock phase/polarity/etc.) */
> >   	if (of_property_read_bool(nc, "spi-cpha")) @@ -2295,14 +2363,52
> @@
> > static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
> >   		return 0;
> >   	}
> >
> > +	if (ctlr->num_chipselect > SPI_CS_CNT_MAX) {
> > +		dev_err(&ctlr->dev, "No. of CS is more than max. no. of
> supported CS\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	/*
> > +	 * Zero(0) is a valid physical CS value and can be located at any
> > +	 * logical CS in the spi->chip_select[]. If all the physical CS
> > +	 * are initialized to 0 then It would be difficult to differentiate
> > +	 * between a valid physical CS 0 & an unused logical CS whose
> physical
> > +	 * CS can be 0. As a solution to this issue initialize all the CS to 0xFF.
> > +	 * Now all the unused logical CS will have 0xFF physical CS value & can
> be
> > +	 * ignore while performing physical CS validity checks.
> > +	 */
> > +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++)
> > +		spi_set_chipselect(spi, idx, 0xFF);
> > +
> >   	/* Device address */
> > -	rc = of_property_read_u32(nc, "reg", &value);
> > -	if (rc) {
> > +	rc = of_property_read_variable_u32_array(nc, "reg", &cs[0], 1,
> > +						 SPI_CS_CNT_MAX);
> > +	if (rc < 0) {
> >   		dev_err(&ctlr->dev, "%pOF has no valid 'reg' property
> (%d)\n",
> >   			nc, rc);
> >   		return rc;
> >   	}
> > -	spi_set_chipselect(spi, 0, value);
> > +	if (rc > ctlr->num_chipselect) {
> > +		dev_err(&ctlr->dev, "%pOF has number of CS > ctlr-
> >num_chipselect (%d)\n",
> > +			nc, rc);
> > +		return rc;
> > +	}
> > +	if ((of_property_read_bool(nc, "parallel-memories")) &&
> > +	    (!(ctlr->flags & SPI_CONTROLLER_MULTI_CS))) {
> > +		dev_err(&ctlr->dev, "SPI controller doesn't support multi
> CS\n");
> > +		return -EINVAL;
> > +	}
> > +	for (idx = 0; idx < rc; idx++)
> > +		spi_set_chipselect(spi, idx, cs[idx]);
> > +
> > +	/* spi->chip_select[i] gives the corresponding physical CS for logical CS
> i
> > +	 * logical CS number is represented by setting the ith bit in spi-
> >cs_index_mask
> > +	 * So, for example, if spi->cs_index_mask = 0x01 then logical CS
> number is 0 and
> > +	 * spi->chip_select[0] will give the physical CS.
> > +	 * By default spi->chip_select[0] will hold the physical CS number so,
> set
> > +	 * spi->cs_index_mask as 0x01.
> > +	 */
> > +	spi->cs_index_mask = 0x01;
> >
> >   	/* Device speed */
> >   	if (!of_property_read_u32(nc, "spi-max-frequency", &value)) @@
> > -3100,6 +3206,7 @@ int spi_register_controller(struct spi_controller *ctlr)
> >   	struct boardinfo	*bi;
> >   	int			first_dynamic;
> >   	int			status;
> > +	int			idx;
> >
> >   	if (!dev)
> >   		return -ENODEV;
> > @@ -3164,7 +3271,8 @@ int spi_register_controller(struct spi_controller
> *ctlr)
> >   	}
> >
> >   	/* Setting last_cs to -1 means no chip selected */
> > -	ctlr->last_cs = -1;
> > +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++)
> > +		ctlr->last_cs[idx] = -1;
> >
> >   	status = device_add(&ctlr->dev);
> >   	if (status < 0)
> > @@ -3889,7 +3997,7 @@ static int __spi_validate(struct spi_device *spi,
> struct spi_message *message)
> >   	 * cs_change is set for each transfer.
> >   	 */
> >   	if ((spi->mode & SPI_CS_WORD) && (!(ctlr->mode_bits &
> SPI_CS_WORD) ||
> > -					  spi_get_csgpiod(spi, 0))) {
> > +					  spi_is_csgpiod(spi))) {
> >   		size_t maxsize = BITS_TO_BYTES(spi->bits_per_word);
> >   		int ret;
> >
> > diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index
> > 7b4baff63c5c..871d3a6d879b 100644
> > --- a/include/linux/spi/spi.h
> > +++ b/include/linux/spi/spi.h
> > @@ -20,6 +20,9 @@
> >
> >   #include <uapi/linux/spi/spi.h>
> >
> > +/* Max no. of CS supported per spi device */ #define SPI_CS_CNT_MAX 4
> > +
> >   struct dma_chan;
> >   struct software_node;
> >   struct ptp_system_timestamp;
> > @@ -132,7 +135,8 @@ extern void
> spi_transfer_cs_change_delay_exec(struct spi_message *msg,
> >    * @max_speed_hz: Maximum clock rate to be used with this chip
> >    *	(on this board); may be changed by the device's driver.
> >    *	The spi_transfer.speed_hz can override this for each transfer.
> > - * @chip_select: Chipselect, distinguishing chips handled by @controller.
> > + * @chip_select: Array of physical chipselect, spi->chipselect[i] gives
> > + *	the corresponding physical CS for logical CS i.
> >    * @mode: The spi mode defines how data is clocked out and in.
> >    *	This may be changed by the device's driver.
> >    *	The "active low" default for chipselect mode can be overridden
> > @@ -157,8 +161,8 @@ extern void
> spi_transfer_cs_change_delay_exec(struct spi_message *msg,
> >    *	the device will bind to the named driver and only the named driver.
> >    *	Do not set directly, because core frees it; use driver_set_override() to
> >    *	set or clear it.
> > - * @cs_gpiod: GPIO descriptor of the chipselect line (optional, NULL when
> > - *	not using a GPIO line)
> > + * @cs_gpiod: Array of GPIO descriptors of the corresponding chipselect
> lines
> > + *	(optional, NULL when not using a GPIO line)
> >    * @word_delay: delay to be inserted between consecutive
> >    *	words of a transfer
> >    * @cs_setup: delay to be introduced by the controller after CS is
> > asserted @@ -167,6 +171,7 @@ extern void
> spi_transfer_cs_change_delay_exec(struct spi_message *msg,
> >    *	deasserted. If @cs_change_delay is used from @spi_transfer, then
> the
> >    *	two delays will be added up.
> >    * @pcpu_statistics: statistics for the spi_device
> > + * @cs_index_mask: Bit mask of the active chipselect(s) in the
> > + chipselect array
> >    *
> >    * A @spi_device is used to interchange data between an SPI slave
> >    * (usually a discrete chip) and CPU memory.
> > @@ -182,7 +187,7 @@ struct spi_device {
> >   	struct spi_controller	*controller;
> >   	struct spi_controller	*master;	/* Compatibility layer */
> >   	u32			max_speed_hz;
> > -	u8			chip_select;
> > +	u8			chip_select[SPI_CS_CNT_MAX];
> >   	u8			bits_per_word;
> >   	bool			rt;
> >   #define SPI_NO_TX		BIT(31)		/* No transmit wire */
> > @@ -213,7 +218,7 @@ struct spi_device {
> >   	void			*controller_data;
> >   	char			modalias[SPI_NAME_SIZE];
> >   	const char		*driver_override;
> > -	struct gpio_desc	*cs_gpiod;	/* Chip select GPIO descriptor
> */
> > +	struct gpio_desc	*cs_gpiod[SPI_CS_CNT_MAX];	/* Chip select
> gpio desc */
> >   	struct spi_delay	word_delay; /* Inter-word delay */
> >   	/* CS delays */
> >   	struct spi_delay	cs_setup;
> > @@ -223,6 +228,13 @@ struct spi_device {
> >   	/* The statistics */
> >   	struct spi_statistics __percpu	*pcpu_statistics;
> >
> > +	/* Bit mask of the chipselect(s) that the driver need to use from
> > +	 * the chipselect array.When the controller is capable to handle
> > +	 * multiple chip selects & memories are connected in parallel
> > +	 * then more than one bit need to be set in cs_index_mask.
> > +	 */
> > +	u32			cs_index_mask : SPI_CS_CNT_MAX;
> > +
> >   	/*
> >   	 * Likely need more hooks for more protocol options affecting how
> >   	 * the controller talks to each chip, like:
> > @@ -279,22 +291,33 @@ static inline void *spi_get_drvdata(const struct
> > spi_device *spi)
> >
> >   static inline u8 spi_get_chipselect(const struct spi_device *spi, u8 idx)
> >   {
> > -	return spi->chip_select;
> > +	return spi->chip_select[idx];
> >   }
> >
> >   static inline void spi_set_chipselect(struct spi_device *spi, u8 idx, u8
> chipselect)
> >   {
> > -	spi->chip_select = chipselect;
> > +	spi->chip_select[idx] = chipselect;
> >   }
> >
> >   static inline struct gpio_desc *spi_get_csgpiod(const struct spi_device *spi,
> u8 idx)
> >   {
> > -	return spi->cs_gpiod;
> > +	return spi->cs_gpiod[idx];
> >   }
> >
> >   static inline void spi_set_csgpiod(struct spi_device *spi, u8 idx, struct
> gpio_desc *csgpiod)
> >   {
> > -	spi->cs_gpiod = csgpiod;
> > +	spi->cs_gpiod[idx] = csgpiod;
> > +}
> > +
> > +static inline bool spi_is_csgpiod(struct spi_device *spi) {
> > +	u8 idx;
> > +
> > +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> > +		if (spi_get_csgpiod(spi, idx))
> > +			return true;
> > +	}
> > +	return false;
> >   }
> >
> >   /**
> > @@ -399,6 +422,8 @@ extern struct spi_device
> *spi_new_ancillary_device(struct spi_device *spi, u8 ch
> >    * @bus_lock_spinlock: spinlock for SPI bus locking
> >    * @bus_lock_mutex: mutex for exclusion of multiple callers
> >    * @bus_lock_flag: indicates that the SPI bus is locked for
> > exclusive use
> > + * @multi_cs_cap: indicates that the SPI Controller can assert/de-assert
> > + *	more than one chip select at once.
> >    * @setup: updates the device mode and clocking records used by a
> >    *	device's SPI controller; protocol code may call this.  This
> >    *	must fail if an unrecognized or unsupported mode is requested.
> > @@ -567,6 +592,11 @@ struct spi_controller {
> >   #define SPI_CONTROLLER_MUST_TX		BIT(4)	/* Requires tx */
> >   #define SPI_CONTROLLER_GPIO_SS		BIT(5)	/* GPIO CS must
> select slave */
> >   #define SPI_CONTROLLER_SUSPENDED	BIT(6)	/* Currently
> suspended */
> > +	/*
> > +	 * The spi-controller has multi chip select capability and can
> > +	 * assert/de-assert more than one chip select at once.
> > +	 */
> > +#define SPI_CONTROLLER_MULTI_CS		BIT(7)
> >
> >   	/* Flag indicating if the allocation of this struct is devres-managed */
> >   	bool			devm_allocated;
> > @@ -677,7 +707,8 @@ struct spi_controller {
> >   	bool				rt;
> >   	bool				auto_runtime_pm;
> >   	bool				cur_msg_mapped;
> > -	char				last_cs;
> > +	char				last_cs[SPI_CS_CNT_MAX];
> > +	char				last_cs_index_mask;
> >   	bool				last_cs_mode_high;
> >   	bool                            fallback;
> >   	struct completion               xfer_completion;

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