[v3,2/3] spi: Add SPI_NO_TX/RX support
diff mbox series

Message ID 20201127130834.136348-2-alexandru.ardelean@analog.com
State New, archived
Headers show
Series
  • [v3,1/3] spi: uapi: unify SPI modes into a single spi.h header
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Commit Message

Alexandru Ardelean Nov. 27, 2020, 1:08 p.m. UTC
From: Dragos Bogdan <dragos.bogdan@analog.com>

Transmit/receive only is a valid SPI mode. For example, the MOSI/TX line
might be missing from an ADC while for a DAC the MISO/RX line may be
optional. This patch adds these two new modes: SPI_NO_TX and
SPI_NO_RX. This way, the drivers will be able to identify if any of
these two lines is missing and to adjust the transfers accordingly.

Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 drivers/spi/spi.c            | 26 +++++++++++++++++++++-----
 include/uapi/linux/spi/spi.h |  2 ++
 2 files changed, 23 insertions(+), 5 deletions(-)

Comments

Andy Shevchenko Nov. 27, 2020, 2:22 p.m. UTC | #1
On Fri, Nov 27, 2020 at 3:08 PM Alexandru Ardelean
<alexandru.ardelean@analog.com> wrote:
> Transmit/receive only is a valid SPI mode. For example, the MOSI/TX line
> might be missing from an ADC while for a DAC the MISO/RX line may be
> optional. This patch adds these two new modes: SPI_NO_TX and
> SPI_NO_RX. This way, the drivers will be able to identify if any of
> these two lines is missing and to adjust the transfers accordingly.

...

> +       /*
> +        * check mode to prevent that any two of DUAL, QUAD and NO_MOSI/MISO
> +        * are set at the same time
>          */

Since you are here,
 check -> Check
 time -> time.

...

> +       if ((hweight_long(spi->mode &
> +               (SPI_TX_DUAL | SPI_TX_QUAD | SPI_NO_TX)) > 1) ||
> +           (hweight_long(spi->mode &
> +               (SPI_RX_DUAL | SPI_RX_QUAD | SPI_NO_RX)) > 1)) {
>                 dev_err(&spi->dev,
> -               "setup: can not select dual and quad at the same time\n");
> +               "setup: can not select any two of dual, quad and no-rx/tx "
> +               "at the same time\n");

Don't split literals, and probably rephrase (If I can't set 2, can I set 3?)
   "setup: can't select more than one out of dual, quad, and no-Rx /
no-Tx at the same time\n");

> --- a/include/uapi/linux/spi/spi.h
> +++ b/include/uapi/linux/spi/spi.h
> @@ -43,5 +43,7 @@
>  #define        SPI_TX_OCTAL            0x2000          /* transmit with 8 wires */
>  #define        SPI_RX_OCTAL            0x4000          /* receive with 8 wires */
>  #define        SPI_3WIRE_HIZ           0x8000          /* high impedance turnaround */
> +#define        SPI_NO_TX               0x10000         /* no transmit wire */
> +#define        SPI_NO_RX               0x20000         /* no receive wire */

Is it really material for uAPI?
Perhaps we may have something like
SPI_MODE_USER_MASK in uAPI and
in internal headers

SPI_MODE_KERNEL_MASK with
static_assert(_USER_MASK & _KERNEL_MASK); // check conditional

?
Andy Shevchenko Nov. 27, 2020, 2:23 p.m. UTC | #2
On Fri, Nov 27, 2020 at 4:22 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> On Fri, Nov 27, 2020 at 3:08 PM Alexandru Ardelean
> <alexandru.ardelean@analog.com> wrote:

...

> > --- a/include/uapi/linux/spi/spi.h
> > +++ b/include/uapi/linux/spi/spi.h
> > @@ -43,5 +43,7 @@
> >  #define        SPI_TX_OCTAL            0x2000          /* transmit with 8 wires */
> >  #define        SPI_RX_OCTAL            0x4000          /* receive with 8 wires */
> >  #define        SPI_3WIRE_HIZ           0x8000          /* high impedance turnaround */
> > +#define        SPI_NO_TX               0x10000         /* no transmit wire */
> > +#define        SPI_NO_RX               0x20000         /* no receive wire */
>
> Is it really material for uAPI?
> Perhaps we may have something like
> SPI_MODE_USER_MASK in uAPI and
> in internal headers
>
> SPI_MODE_KERNEL_MASK with
> static_assert(_USER_MASK & _KERNEL_MASK); // check conditional
>
> ?

And logically start bits for the kernel from the end (31, 30, ...).
Alexandru Ardelean Dec. 3, 2020, 8:20 a.m. UTC | #3
> -----Original Message-----
> From: Andy Shevchenko <andy.shevchenko@gmail.com>
> Sent: Friday, November 27, 2020 4:24 PM
> To: Ardelean, Alexandru <alexandru.Ardelean@analog.com>
> Cc: linux-spi <linux-spi@vger.kernel.org>; devicetree
> <devicetree@vger.kernel.org>; Linux Kernel Mailing List <linux-
> kernel@vger.kernel.org>; Rob Herring <robh+dt@kernel.org>; Mark Brown
> <broonie@kernel.org>; Bogdan, Dragos <Dragos.Bogdan@analog.com>
> Subject: Re: [PATCH v3 2/3] spi: Add SPI_NO_TX/RX support
> 
> On Fri, Nov 27, 2020 at 4:22 PM Andy Shevchenko
> <andy.shevchenko@gmail.com> wrote:
> > On Fri, Nov 27, 2020 at 3:08 PM Alexandru Ardelean
> > <alexandru.ardelean@analog.com> wrote:
> 
> ...
> 
> > > --- a/include/uapi/linux/spi/spi.h
> > > +++ b/include/uapi/linux/spi/spi.h
> > > @@ -43,5 +43,7 @@
> > >  #define        SPI_TX_OCTAL            0x2000          /* transmit with 8 wires */
> > >  #define        SPI_RX_OCTAL            0x4000          /* receive with 8 wires */
> > >  #define        SPI_3WIRE_HIZ           0x8000          /* high impedance turnaround
> */
> > > +#define        SPI_NO_TX               0x10000         /* no transmit wire */
> > > +#define        SPI_NO_RX               0x20000         /* no receive wire */
> >
> > Is it really material for uAPI?
> > Perhaps we may have something like
> > SPI_MODE_USER_MASK in uAPI and
> > in internal headers

Hmm, in a way this could make sense for some SPIDEVs as well, to set these flags and get an error if they try to TX with the NO_TX flag set.
Not really sure about this.
Initially I mechanically added these here as an inertia to the previous patch which is just unifying the headers.

Any other opinions? Thoughts?
Mark?

> >
> > SPI_MODE_KERNEL_MASK with
> > static_assert(_USER_MASK & _KERNEL_MASK); // check conditional
> >
> > ?
> 
> And logically start bits for the kernel from the end (31, 30, ...).
> 
> --
> With Best Regards,
> Andy Shevchenko
Mark Brown Dec. 3, 2020, 9:47 a.m. UTC | #4
On Thu, Dec 03, 2020 at 08:20:57AM +0000, Ardelean, Alexandru wrote:

> > > > @@ -43,5 +43,7 @@
> > > >  #define        SPI_TX_OCTAL            0x2000          /* transmit with 8 wires */
> > > >  #define        SPI_RX_OCTAL            0x4000          /* receive with 8 wires */
> > > >  #define        SPI_3WIRE_HIZ           0x8000          /* high impedance turnaround
> > */
> > > > +#define        SPI_NO_TX               0x10000         /* no transmit wire */
> > > > +#define        SPI_NO_RX               0x20000         /* no receive wire */

> > > Is it really material for uAPI?
> > > Perhaps we may have something like
> > > SPI_MODE_USER_MASK in uAPI and
> > > in internal headers

> Hmm, in a way this could make sense for some SPIDEVs as well, to set these flags and get an error if they try to TX with the NO_TX flag set.
> Not really sure about this.
> Initially I mechanically added these here as an inertia to the previous patch which is just unifying the headers.

> Any other opinions? Thoughts?
> Mark?

spidev is hacky at the best of times...  It *is* probably better to only
have the usefully mainpulable modes exposed in uapi and then define the
rest internally though.

Patch
diff mbox series

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index cd3c395b4e90..17d4004bd2c6 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1941,6 +1941,9 @@  static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
 	/* Device DUAL/QUAD mode */
 	if (!of_property_read_u32(nc, "spi-tx-bus-width", &value)) {
 		switch (value) {
+		case 0:
+			spi->mode |= SPI_NO_TX;
+			break;
 		case 1:
 			break;
 		case 2:
@@ -1962,6 +1965,9 @@  static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
 
 	if (!of_property_read_u32(nc, "spi-rx-bus-width", &value)) {
 		switch (value) {
+		case 0:
+			spi->mode |= SPI_NO_RX;
+			break;
 		case 1:
 			break;
 		case 2:
@@ -3329,12 +3335,17 @@  int spi_setup(struct spi_device *spi)
 	unsigned	bad_bits, ugly_bits;
 	int		status;
 
-	/* check mode to prevent that DUAL and QUAD set at the same time
+	/*
+	 * check mode to prevent that any two of DUAL, QUAD and NO_MOSI/MISO
+	 * are set at the same time
 	 */
-	if (((spi->mode & SPI_TX_DUAL) && (spi->mode & SPI_TX_QUAD)) ||
-		((spi->mode & SPI_RX_DUAL) && (spi->mode & SPI_RX_QUAD))) {
+	if ((hweight_long(spi->mode &
+		(SPI_TX_DUAL | SPI_TX_QUAD | SPI_NO_TX)) > 1) ||
+	    (hweight_long(spi->mode &
+		(SPI_RX_DUAL | SPI_RX_QUAD | SPI_NO_RX)) > 1)) {
 		dev_err(&spi->dev,
-		"setup: can not select dual and quad at the same time\n");
+		"setup: can not select any two of dual, quad and no-rx/tx "
+		"at the same time\n");
 		return -EINVAL;
 	}
 	/* if it is SPI_3WIRE mode, DUAL and QUAD should be forbidden
@@ -3348,7 +3359,8 @@  int spi_setup(struct spi_device *spi)
 	 * SPI_CS_WORD has a fallback software implementation,
 	 * so it is ignored here.
 	 */
-	bad_bits = spi->mode & ~(spi->controller->mode_bits | SPI_CS_WORD);
+	bad_bits = spi->mode & ~(spi->controller->mode_bits | SPI_CS_WORD |
+				 SPI_NO_TX | SPI_NO_RX);
 	/* nothing prevents from working with active-high CS in case if it
 	 * is driven by GPIO.
 	 */
@@ -3609,6 +3621,8 @@  static int __spi_validate(struct spi_device *spi, struct spi_message *message)
 		 * 2. check tx/rx_nbits match the mode in spi_device
 		 */
 		if (xfer->tx_buf) {
+			if (spi->mode & SPI_NO_TX)
+				return -EINVAL;
 			if (xfer->tx_nbits != SPI_NBITS_SINGLE &&
 				xfer->tx_nbits != SPI_NBITS_DUAL &&
 				xfer->tx_nbits != SPI_NBITS_QUAD)
@@ -3622,6 +3636,8 @@  static int __spi_validate(struct spi_device *spi, struct spi_message *message)
 		}
 		/* check transfer rx_nbits */
 		if (xfer->rx_buf) {
+			if (spi->mode & SPI_NO_RX)
+				return -EINVAL;
 			if (xfer->rx_nbits != SPI_NBITS_SINGLE &&
 				xfer->rx_nbits != SPI_NBITS_DUAL &&
 				xfer->rx_nbits != SPI_NBITS_QUAD)
diff --git a/include/uapi/linux/spi/spi.h b/include/uapi/linux/spi/spi.h
index ae028d64c779..b504e46a6f18 100644
--- a/include/uapi/linux/spi/spi.h
+++ b/include/uapi/linux/spi/spi.h
@@ -43,5 +43,7 @@ 
 #define	SPI_TX_OCTAL		0x2000		/* transmit with 8 wires */
 #define	SPI_RX_OCTAL		0x4000		/* receive with 8 wires */
 #define	SPI_3WIRE_HIZ		0x8000		/* high impedance turnaround */
+#define	SPI_NO_TX		0x10000		/* no transmit wire */
+#define	SPI_NO_RX		0x20000		/* no receive wire */
 
 #endif /* _UAPI_SPI_H */