[PATCH v4 38/40] spi: fsi: Calculate clock divider from local bus frequency

Eddie James
2024-06-05T21:23:44Z

Use the new FSI device local bus clock to calculate the proper SPI
clock divider.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Acked-by: Mark Brown <broonie@kernel.org>
---
drivers/spi/spi-fsi.c | 33 ++++++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-fsi.c b/drivers/spi/spi-fsi.c
index fc9e33be1e0e7..e762690f1a390 100644
--- a/drivers/spi/spi-fsi.c
+++ b/drivers/spi/spi-fsi.c
@@ -40,6 +40,7 @@
#define SPI_FSI_CLOCK_CFG_SCK_RECV_DEL GENMASK_ULL(51, 44)
#define SPI_FSI_CLOCK_CFG_SCK_NO_DEL BIT_ULL(51)
#define SPI_FSI_CLOCK_CFG_SCK_DIV GENMASK_ULL(63, 52)
+#define SPI_FSI_CLOCK_CFG_SCK_DIV_MIN 0x4
#define SPI_FSI_MMAP 0x4
#define SPI_FSI_DATA_TX 0x5
#define SPI_FSI_DATA_RX 0x6
@@ -70,6 +71,7 @@
struct fsi2spi {
struct fsi_device *fsi; /* FSI2SPI CFAM engine device */
struct mutex lock; /* lock access to the device */
+ u32 lbus_freq;
};

struct fsi_spi {
@@ -359,7 +361,7 @@ static int fsi_spi_transfer_data(struct fsi_spi *ctx,
return 0;
}

-static int fsi_spi_transfer_init(struct fsi_spi *ctx)
+static int fsi_spi_transfer_init(struct fsi_spi *ctx, u32 clock_div)
{
int loops = 0;
int rc;
@@ -370,7 +372,7 @@ static int fsi_spi_transfer_init(struct fsi_spi *ctx)
u64 status = 0ULL;
u64 wanted_clock_cfg = SPI_FSI_CLOCK_CFG_ECC_DISABLE |
SPI_FSI_CLOCK_CFG_SCK_NO_DEL |
- FIELD_PREP(SPI_FSI_CLOCK_CFG_SCK_DIV, 19);
+ FIELD_PREP(SPI_FSI_CLOCK_CFG_SCK_DIV, clock_div);

end = jiffies + msecs_to_jiffies(SPI_FSI_TIMEOUT_MS);
do {
@@ -421,6 +423,24 @@ static int fsi_spi_transfer_init(struct fsi_spi *ctx)
return rc;
}

+static u32 fsi_spi_calculate_clock_div(struct fsi2spi *bridge, struct spi_device *dev,
+ struct spi_transfer *transfer)
+{
+ u32 div = 19;
+
+ if (bridge->lbus_freq) {
+ u32 desired_speed_hz = transfer->speed_hz ?: dev->max_speed_hz;
+
+ div = DIV_ROUND_UP(bridge->lbus_freq, desired_speed_hz);
+ if (div < SPI_FSI_CLOCK_CFG_SCK_DIV_MIN)
+ div = SPI_FSI_CLOCK_CFG_SCK_DIV_MIN;
+
+ transfer->effective_speed_hz = bridge->lbus_freq / div;
+ }
+
+ return div;
+}
+
static int fsi_spi_transfer_one_message(struct spi_controller *ctlr,
struct spi_message *mesg)
{
@@ -429,6 +449,7 @@ static int fsi_spi_transfer_one_message(struct spi_controller *ctlr,
unsigned int len;
struct spi_transfer *transfer;
struct fsi_spi *ctx = spi_controller_get_devdata(ctlr);
+ u32 div;

rc = fsi_spi_check_mux(ctx->bridge->fsi, ctx->dev);
if (rc)
@@ -446,7 +467,8 @@ static int fsi_spi_transfer_one_message(struct spi_controller *ctlr,

dev_dbg(ctx->dev, "Start tx of %d bytes.\n", transfer->len);

- rc = fsi_spi_transfer_init(ctx);
+ div = fsi_spi_calculate_clock_div(ctx->bridge, mesg->spi, transfer);
+ rc = fsi_spi_transfer_init(ctx, div);
if (rc < 0)
goto error;

@@ -533,6 +555,7 @@ static int fsi_spi_probe(struct device *dev)

bridge->fsi = fsi;
mutex_init(&bridge->lock);
+ bridge->lbus_freq = fsi_device_local_bus_frequency(fsi);

for_each_available_child_of_node(dev->of_node, np) {
u32 base;
@@ -550,6 +573,10 @@ static int fsi_spi_probe(struct device *dev)

ctlr->dev.of_node = np;
ctlr->num_chipselect = of_get_available_child_count(np) ?: 1;
+ if (bridge->lbus_freq) {
+ ctlr->min_speed_hz = DIV_ROUND_UP(bridge->lbus_freq, 0xfff);
+ ctlr->max_speed_hz = bridge->lbus_freq / SPI_FSI_CLOCK_CFG_SCK_DIV_MIN;
+ }
ctlr->flags = SPI_CONTROLLER_HALF_DUPLEX;
ctlr->max_transfer_size = fsi_spi_max_transfer_size;
ctlr->transfer_one_message = fsi_spi_transfer_one_message;
--
2.39.3