[PATCH RESEND v3 0/4] spi: dw: Auto-detect number of native CS

[PATCH RESEND v3 0/4] spi: dw: Auto-detect number of native CS

[Serge Semin]

The main goal of the short series is to provide a procedure implementing
the auto-detection of the number of native Chip-Select signals supported
by the controller. The suggested algorithm is straightforward. It relies
on the fact that the SER register writable flags reflects the actual
number of available native chip-select signals. So the DW APB/AHB SSI
driver now tests the SER register for having the writable bits,
calculates the number of CS signals based on the number of set flags and
then initializes the num_cs private data field based on that, which then
will be passed to the SPI-core subsystem indicating the number of
supported hardware chip-selects. The implemented procedure will be useful
for the DW SSI device nodes not having the explicitly set "num-cs"
property. In case if the property is specified it will be utilized instead
of the auto-detection procedure.

Besides of that a small cleanup patch is introduced in the head of the
series. It converts the driver to using the BITS_TO_BYTES() macro instead
of the hard-coded DIV_ROUND_UP()-based calculation of the number of
bytes-per-transfer-word.

Link: https://lore.kernel.org/linux-spi/20240215180102.13887-1-fancer.lancer@gmail.com
Changelog v2:
- Add a new patch:
  [PATCH v2 3/4] spi: dw: Convert dw_spi::num_cs to u32
- Fix some spelling notes (@Andy).

Link: https://lore.kernel.org/linux-spi/20240222172853.25082-1-fancer.lancer@gmail.com/
Changelog v3:
- Add Andy' Rb tag.
- Rebase onto the kernel v6.9 and resubmit.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: linux-spi@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Serge Semin (4):
  spi: dw: Convert to using BITS_TO_BYTES() macro
  spi: dw: Add a number of native CS auto-detection
  spi: dw: Convert dw_spi::num_cs to u32
  spi: dw: Drop default number of CS setting

 drivers/spi/spi-dw-core.c | 20 ++++++++++++++++----
 drivers/spi/spi-dw-mmio.c |  8 ++------
 drivers/spi/spi-dw.h      |  2 +-
 3 files changed, 19 insertions(+), 11 deletions(-)

-- 
2.43.0

[PATCH RESEND v3 1/4] spi: dw: Convert to using BITS_TO_BYTES() macro

[Serge Semin]

Since commit dd3e7cba1627 ("ocfs2/dlm: move BITS_TO_BYTES() to bitops.h
for wider use") there is a generic helper available to calculate a number
of bytes needed to accommodate the specified number of bits. Let's use it
instead of the hard-coded DIV_ROUND_UP() macro function.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 drivers/spi/spi-dw-core.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
index 0274c9295514..722b5eb1f709 100644
--- a/drivers/spi/spi-dw-core.c
+++ b/drivers/spi/spi-dw-core.c
@@ -6,6 +6,7 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/bitops.h>
 #include <linux/dma-mapping.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
@@ -421,10 +422,7 @@ static int dw_spi_transfer_one(struct spi_controller *host,
 	int ret;
 
 	dws->dma_mapped = 0;
-	dws->n_bytes =
-		roundup_pow_of_two(DIV_ROUND_UP(transfer->bits_per_word,
-						BITS_PER_BYTE));
-
+	dws->n_bytes = roundup_pow_of_two(BITS_TO_BYTES(transfer->bits_per_word));
 	dws->tx = (void *)transfer->tx_buf;
 	dws->tx_len = transfer->len / dws->n_bytes;
 	dws->rx = transfer->rx_buf;
-- 
2.43.0

[PATCH RESEND v3 2/4] spi: dw: Add a number of native CS auto-detection

[Serge Semin]

Aside with the FIFO depth and DFS field size it's possible to auto-detect
a number of native chip-select synthesized in the DW APB/AHB SSI IP-core.
It can be done just by writing ones to the SER register. The number of
writable flags in the register is limited by the SSI_NUM_SLAVES IP-core
synthesize parameter. All the upper flags are read-only and wired to zero.
Based on that let's add the number of native CS auto-detection procedure
so the low-level platform drivers wouldn't need to manually set it up
unless it's required to set a constraint due to platform-specific reasons
(for instance, due to a hardware bug).

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
---
 drivers/spi/spi-dw-core.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
index 722b5eb1f709..ddfdb903047a 100644
--- a/drivers/spi/spi-dw-core.c
+++ b/drivers/spi/spi-dw-core.c
@@ -834,6 +834,20 @@ static void dw_spi_hw_init(struct device *dev, struct dw_spi *dws)
 			DW_SPI_GET_BYTE(dws->ver, 1));
 	}
 
+	/*
+	 * Try to detect the number of native chip-selects if the platform
+	 * driver didn't set it up. There can be up to 16 lines configured.
+	 */
+	if (!dws->num_cs) {
+		u32 ser;
+
+		dw_writel(dws, DW_SPI_SER, 0xffff);
+		ser = dw_readl(dws, DW_SPI_SER);
+		dw_writel(dws, DW_SPI_SER, 0);
+
+		dws->num_cs = hweight16(ser);
+	}
+
 	/*
 	 * Try to detect the FIFO depth if not set by interface driver,
 	 * the depth could be from 2 to 256 from HW spec
-- 
2.43.0

[PATCH RESEND v3 3/4] spi: dw: Convert dw_spi::num_cs to u32

[Serge Semin]

Number of native chip-select lines is either retrieved from the "num-cs"
DT-property or auto-detected in the generic DW APB/AHB SSI probe method.
In the former case the property is supposed to be of the "u32" size.
Convert the field type to being u32 then to be able to drop the temporary
variable afterwards.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>

---

Changelog v2:
- Just added.
---
 drivers/spi/spi-dw.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h
index 6cafeee8ee2a..fc267c6437ae 100644
--- a/drivers/spi/spi-dw.h
+++ b/drivers/spi/spi-dw.h
@@ -164,8 +164,8 @@ struct dw_spi {
 	u32			max_freq;	/* max bus freq supported */
 
 	u32			reg_io_width;	/* DR I/O width in bytes */
+	u32			num_cs;		/* chip select lines */
 	u16			bus_num;
-	u16			num_cs;		/* supported slave numbers */
 	void (*set_cs)(struct spi_device *spi, bool enable);
 
 	/* Current message transfer state info */
-- 
2.43.0

[PATCH RESEND v3 4/4] spi: dw: Drop default number of CS setting

[Serge Semin]

DW APB/AHB SSI core now supports the procedure automatically detecting the
number of native chip-select lines. Thus there is no longer point in
defaulting to four CS if the platform doesn't specify the real number
especially seeing the default number didn't correspond to any original DW
APB/AHB databook.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>

---

Changelog v2:
- Drop temporal variable and pass dws_spi::num_cs directly.
---
 drivers/spi/spi-dw-mmio.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
index cc74cbe03431..c56de35eca98 100644
--- a/drivers/spi/spi-dw-mmio.c
+++ b/drivers/spi/spi-dw-mmio.c
@@ -320,7 +320,6 @@ static int dw_spi_mmio_probe(struct platform_device *pdev)
 	struct resource *mem;
 	struct dw_spi *dws;
 	int ret;
-	int num_cs;
 
 	dwsmmio = devm_kzalloc(&pdev->dev, sizeof(struct dw_spi_mmio),
 			GFP_KERNEL);
@@ -364,11 +363,8 @@ static int dw_spi_mmio_probe(struct platform_device *pdev)
 				     &dws->reg_io_width))
 		dws->reg_io_width = 4;
 
-	num_cs = 4;
-
-	device_property_read_u32(&pdev->dev, "num-cs", &num_cs);
-
-	dws->num_cs = num_cs;
+	/* Rely on the auto-detection if no property specified */
+	device_property_read_u32(&pdev->dev, "num-cs", &dws->num_cs);
 
 	init_func = device_get_match_data(&pdev->dev);
 	if (init_func) {
-- 
2.43.0