[PATCH 1/4] spi: add per-driver bits-per-word mask

[PATCH 1/4] spi: add per-driver bits-per-word mask

[Philipp Zabel]

Allow SPI hosts to signal per-transfer bits-per-word switching
support and drivers to query it with spi_is_bpw_supported().

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 include/spi/spi.h | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/include/spi/spi.h b/include/spi/spi.h
index fa9329b08c80..809ebd8df1a8 100644
--- a/include/spi/spi.h
+++ b/include/spi/spi.h
@@ -131,6 +131,11 @@ struct spi_message;
  *	SPI slaves, and are numbered from zero to num_chipselects.
  *	each slave has a chipselect signal, but it's common that not
  *	every chipselect is connected to a slave.
+ * @bits_per_word_mask: A mask indicating which values of bits_per_word are
+ *	supported by the driver. Bit n indicates that a bits_per_word n+1 is
+ *	supported. If set, the SPI core will reject any transfer with an
+ *	unsupported bits_per_word. If not set, this value is simply ignored,
+ *	and it's up to the individual driver to perform any validation.
  * @max_speed_hz: Highest supported transfer speed
  * @setup: updates the device mode and clocking records used by a
  *	device's SPI controller; protocol code may call this.  This
@@ -165,6 +170,12 @@ struct spi_controller {
 
 	/* Optimized handlers for SPI memory-like operations */
 	const struct spi_controller_mem_ops *mem_ops;
+
+	/* Bitmask of supported bits_per_word for transfers */
+	u32			bits_per_word_mask;
+#define SPI_BPW_MASK(bits) BIT((bits) - 1)
+#define SPI_BPW_RANGE_MASK(min, max) GENMASK((max) - 1, (min) - 1)
+
 	/*
 	 * on some hardware transfer size may be constrained
 	 * the limit may depend on device transfer settings
@@ -435,6 +446,26 @@ spi_transfer_del(struct spi_transfer *t)
 	list_del(&t->transfer_list);
 }
 
+/**
+ * spi_is_bpw_supported - Check if bits per word is supported
+ * @spi: SPI device
+ * @bpw: Bits per word
+ *
+ * This function checks to see if the SPI controller supports @bpw.
+ *
+ * Returns:
+ * True if @bpw is supported, false otherwise.
+ */
+static inline bool spi_is_bpw_supported(struct spi_device *spi, u32 bpw)
+{
+	u32 bpw_mask = spi->master->bits_per_word_mask;
+
+	if (bpw == 8 || (bpw <= 32 && bpw_mask & SPI_BPW_MASK(bpw)))
+		return true;
+
+	return false;
+}
+
 /* All these synchronous SPI transfer routines are utilities layered
  * over the core async transfer primitive.  Here, "synchronous" means
  * they will sleep uninterruptibly until the async transfer completes.
-- 
2.39.2

[PATCH 2/4] spi: stm32: support per-transfer bits per word switching

[Philipp Zabel]

Allow dynamically switching data size between transfers.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 drivers/spi/stm32_spi.c | 50 ++++++++++++++++++++++++++++++++---------
 1 file changed, 39 insertions(+), 11 deletions(-)

diff --git a/drivers/spi/stm32_spi.c b/drivers/spi/stm32_spi.c
index 0d7407c279a2..1ac86fbe11e6 100644
--- a/drivers/spi/stm32_spi.c
+++ b/drivers/spi/stm32_spi.c
@@ -111,6 +111,24 @@ static inline struct stm32_spi_priv *to_stm32_spi_priv(struct spi_master *master
 	return container_of(master, struct stm32_spi_priv, master);
 }
 
+static int stm32_spi_get_bpw_mask(struct stm32_spi_priv *priv)
+{
+	u32 cfg1, max_bpw;
+
+	/*
+	 * The most significant bit at DSIZE bit field is reserved when the
+	 * maximum data size of periperal instances is limited to 16-bit
+	 */
+	setbits_le32(priv->base + STM32_SPI_CFG1, SPI_CFG1_DSIZE);
+
+	cfg1 = readl(priv->base + STM32_SPI_CFG1);
+	max_bpw = FIELD_GET(SPI_CFG1_DSIZE, cfg1) + 1;
+
+	dev_dbg(priv->master.dev, "%d-bit maximum data frame\n", max_bpw);
+
+	return SPI_BPW_RANGE_MASK(4, max_bpw);
+}
+
 static void stm32_spi_write_txfifo(struct stm32_spi_priv *priv)
 {
 	while ((priv->tx_len > 0) &&
@@ -261,19 +279,15 @@ static void stm32_spi_set_mode(struct stm32_spi_priv *priv, unsigned mode)
 
 static void stm32_spi_set_fthlv(struct stm32_spi_priv *priv, u32 xfer_len)
 {
-	u32 fthlv, half_fifo;
+	u32 fthlv, packet, bpw;
 
 	/* data packet should not exceed 1/2 of fifo space */
-	half_fifo = (priv->fifo_size / 2);
-
-	/* data_packet should not exceed transfer length */
-	fthlv = (half_fifo > xfer_len) ? xfer_len : half_fifo;
+	packet = clamp(xfer_len, 1U, priv->fifo_size / 2);
 
 	/* align packet size with data registers access */
-	fthlv -= (fthlv % 4);
+	bpw = DIV_ROUND_UP(priv->cur_bpw, 8);
+	fthlv = DIV_ROUND_UP(packet, bpw);
 
-	if (!fthlv)
-		fthlv = 1;
 	clrsetbits_le32(priv->base + STM32_SPI_CFG1, SPI_CFG1_FTHLV,
 			(fthlv - 1) << SPI_CFG1_FTHLV_SHIFT);
 }
@@ -344,9 +358,17 @@ static int stm32_spi_transfer_one(struct stm32_spi_priv *priv,
 	u32 ifcr = 0;
 	u32 mode;
 	int xfer_status = 0;
+	int nb_words;
 
-	if (t->len <= SPI_CR2_TSIZE)
-		writel(t->len, priv->base + STM32_SPI_CR2);
+	if (t->bits_per_word <= 8)
+		nb_words = t->len;
+	else if (t->bits_per_word <= 16)
+		nb_words = DIV_ROUND_UP(t->len * 8, 16);
+	else
+		nb_words = DIV_ROUND_UP(t->len * 8, 32);
+
+	if (nb_words <= SPI_CR2_TSIZE)
+		writel(nb_words, priv->base + STM32_SPI_CR2);
 	else
 		return -EMSGSIZE;
 
@@ -361,9 +383,11 @@ static int stm32_spi_transfer_one(struct stm32_spi_priv *priv,
 	else if (!priv->rx_buf)
 		mode = SPI_SIMPLEX_TX;
 
-	if (priv->cur_xferlen != t->len || priv->cur_mode != mode) {
+	if (priv->cur_xferlen != t->len || priv->cur_mode != mode ||
+	    priv->cur_bpw != t->bits_per_word) {
 		priv->cur_mode = mode;
 		priv->cur_xferlen = t->len;
+		priv->cur_bpw = t->bits_per_word;
 
 		/* Disable the SPI hardware to unlock CFG1/CFG2 registers */
 		stm32_spi_disable(priv);
@@ -373,6 +397,9 @@ static int stm32_spi_transfer_one(struct stm32_spi_priv *priv,
 
 		stm32_spi_set_fthlv(priv, t->len);
 
+		clrsetbits_le32(priv->base + STM32_SPI_CFG1, SPI_CFG1_DSIZE,
+				priv->cur_bpw - 1);
+
 		/* Enable the SPI hardware */
 		stm32_spi_enable(priv);
 	}
@@ -543,6 +570,7 @@ static int stm32_spi_probe(struct device *dev)
 	master->transfer = stm32_spi_transfer;
 	master->mem_ops = &stm32_spi_mem_ops;
 
+	master->bits_per_word_mask = stm32_spi_get_bpw_mask(priv);
 	master->bus_num = -1;
 	stm32_spi_dt_probe(priv);
 
-- 
2.39.2

[PATCH 3/4] video: mipi_dbi: disable byte swapping if 16-bit SPI transfers are supported

[Philipp Zabel]

If the SPI controller supports switching to 16-bit transfers, there
is no need to swap bytes on little-endian architectures. This also
allows to transfer directly from the 16-bit framebuffer.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 drivers/video/mipi_dbi.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/video/mipi_dbi.c b/drivers/video/mipi_dbi.c
index e6a147a9bf36..30fba07acfb2 100644
--- a/drivers/video/mipi_dbi.c
+++ b/drivers/video/mipi_dbi.c
@@ -632,8 +632,7 @@ int mipi_dbi_spi_init(struct spi_device *spi, struct mipi_dbi *dbi,
 
 	dbi->command = mipi_dbi_typec3_command;
 	dbi->dc = dc;
-	// TODO: can we just force 16 bit?
-	if (mipi_dbi_machine_little_endian() && spi->bits_per_word != 16)
+	if (mipi_dbi_machine_little_endian() && !spi_is_bpw_supported(spi, 16))
 		dbi->swap_bytes = true;
 
 	dev_dbg(dev, "SPI speed: %uMHz\n", spi->max_speed_hz / 1000000);
-- 
2.39.2

[PATCH 4/4] spi: update spi_board_info FIXME comment

[Philipp Zabel]

The spi-stm32 driver now supports the spi_transfer.bits_per_word
override.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 include/spi/spi.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/spi/spi.h b/include/spi/spi.h
index 809ebd8df1a8..d479e4f34f0c 100644
--- a/include/spi/spi.h
+++ b/include/spi/spi.h
@@ -44,7 +44,7 @@ struct spi_board_info {
  *	This may be changed by the device's driver, or left at the
  *	default (0) indicating protocol words are eight bit bytes.
  *	The spi_transfer.bits_per_word can override this for each transfer
- *	(FIXME: not currently implemented).
+ *	(FIXME: not currently implemented by most drivers).
  * @irq: Negative, or the number passed to request_irq() to receive
  *	interrupts from this device.
  * @controller_state: Controller's runtime state
-- 
2.39.2

Re: [PATCH 2/4] spi: stm32: support per-transfer bits per word switching

[Philipp Zabel]

On Thu, Mar 30, 2023 at 12:33:57PM +0200, Philipp Zabel wrote:
> Allow dynamically switching data size between transfers.
> 
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> ---
>  drivers/spi/stm32_spi.c | 50 ++++++++++++++++++++++++++++++++---------
>  1 file changed, 39 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/spi/stm32_spi.c b/drivers/spi/stm32_spi.c
> index 0d7407c279a2..1ac86fbe11e6 100644
> --- a/drivers/spi/stm32_spi.c
> +++ b/drivers/spi/stm32_spi.c
[...]
> @@ -543,6 +570,7 @@ static int stm32_spi_probe(struct device *dev)
>  	master->transfer = stm32_spi_transfer;
>  	master->mem_ops = &stm32_spi_mem_ops;
>  
> +	master->bits_per_word_mask = stm32_spi_get_bpw_mask(priv);

This has to be moved down a few lines, after the clock is enabled and
the device is reset. I'll fix this in v2.

regards
Philipp

Re: [PATCH 2/4] spi: stm32: support per-transfer bits per word switching

[Sascha Hauer]

On Thu, Mar 30, 2023 at 04:53:09PM +0200, Philipp Zabel wrote:
> On Thu, Mar 30, 2023 at 12:33:57PM +0200, Philipp Zabel wrote:
> > Allow dynamically switching data size between transfers.
> > 
> > Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> > ---
> >  drivers/spi/stm32_spi.c | 50 ++++++++++++++++++++++++++++++++---------
> >  1 file changed, 39 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/spi/stm32_spi.c b/drivers/spi/stm32_spi.c
> > index 0d7407c279a2..1ac86fbe11e6 100644
> > --- a/drivers/spi/stm32_spi.c
> > +++ b/drivers/spi/stm32_spi.c
> [...]
> > @@ -543,6 +570,7 @@ static int stm32_spi_probe(struct device *dev)
> >  	master->transfer = stm32_spi_transfer;
> >  	master->mem_ops = &stm32_spi_mem_ops;
> >  
> > +	master->bits_per_word_mask = stm32_spi_get_bpw_mask(priv);
> 
> This has to be moved down a few lines, after the clock is enabled and
> the device is reset. I'll fix this in v2.

Please do so. Otherwise the series looks good to me.

Sascha

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