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/[email protected]
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/[email protected]
Changelog v3:
- Add Andy' Rb tag.
- Rebase onto the kernel v6.9 and resubmit.
Link: https://lore.kernel.org/linux-spi/[email protected]
Changelog v4:
- Just resend.
Signed-off-by: Serge Semin <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: [email protected]
Cc: [email protected]
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
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 <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
---
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
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 <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
---
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