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Subject[PATCH V1 22/26] spi: tegra114: add support for tuning clock delay
Date
Tegra SPI controller has TX_CLK_TAP_DELAY and RX_CLK_TAP_DELAY in
COMMAND2 register to tune delay of the clock going out to external
device during transmit and also for the clock coming in from external
device during receive.

TX/RX clock tap delays may vary based on the trace lengths of the
platform design for each of the slaves on the SPI bus.

This patch adds support for configuring TX/RX clock delays specified
through device tree properties.

Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
---
drivers/spi/spi-tegra114.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-tegra114.c b/drivers/spi/spi-tegra114.c
index e01962344bde..725d60364ec6 100644
--- a/drivers/spi/spi-tegra114.c
+++ b/drivers/spi/spi-tegra114.c
@@ -174,6 +174,8 @@ struct tegra_spi_client_data {
int cs_setup_clk_count;
int cs_hold_clk_count;
int cs_inactive_cycles;
+ int tx_clk_tap_delay;
+ int rx_clk_tap_delay;
};

struct tegra_spi_data {
@@ -215,8 +217,10 @@ struct tegra_spi_data {
u32 command1_reg;
u32 dma_control_reg;
u32 def_command1_reg;
+ u32 def_command2_reg;
u32 spi_cs_timing1;
u32 spi_cs_timing2;
+ u8 last_used_cs;

struct completion xfer_completion;
struct spi_transfer *curr_xfer;
@@ -780,7 +784,9 @@ static u32 tegra_spi_setup_transfer_one(struct spi_device *spi,
u32 speed = t->speed_hz;
u8 bits_per_word = t->bits_per_word;
u32 command1;
+ u32 command2;
int req_mode;
+ u32 tx_tap = 0, rx_tap = 0;

if (speed != tspi->cur_speed) {
clk_set_rate(tspi->clk, speed);
@@ -843,7 +849,18 @@ static u32 tegra_spi_setup_transfer_one(struct spi_device *spi,
command1 &= ~(SPI_CS_SW_HW | SPI_CS_SW_VAL);
}

- tegra_spi_writel(tspi, 0, SPI_COMMAND2);
+ if (tspi->last_used_cs != spi->chip_select) {
+ if (cdata && cdata->tx_clk_tap_delay)
+ tx_tap = cdata->tx_clk_tap_delay;
+ if (cdata && cdata->rx_clk_tap_delay)
+ rx_tap = cdata->rx_clk_tap_delay;
+ command2 = SPI_TX_TAP_DELAY(tx_tap) |
+ SPI_RX_TAP_DELAY(rx_tap);
+ if (command2 != tspi->def_command2_reg)
+ tegra_spi_writel(tspi, command2, SPI_COMMAND2);
+ tspi->last_used_cs = spi->chip_select;
+ }
+
} else {
command1 = tspi->command1_reg;
command1 &= ~SPI_BIT_LENGTH(~0);
@@ -923,6 +940,10 @@ static struct tegra_spi_client_data
&cdata->cs_hold_clk_count);
of_property_read_u32(slave_np, "nvidia,cs-inactive-cycles",
&cdata->cs_inactive_cycles);
+ of_property_read_u32(slave_np, "nvidia,tx-clk-tap-delay",
+ &cdata->tx_clk_tap_delay);
+ of_property_read_u32(slave_np, "nvidia,rx-clk-tap-delay",
+ &cdata->rx_clk_tap_delay);
return cdata;
}

@@ -1379,6 +1400,8 @@ static int tegra_spi_probe(struct platform_device *pdev)
tegra_spi_writel(tspi, tspi->def_command1_reg, SPI_COMMAND1);
tspi->spi_cs_timing1 = tegra_spi_readl(tspi, SPI_CS_TIMING1);
tspi->spi_cs_timing2 = tegra_spi_readl(tspi, SPI_CS_TIMING2);
+ tspi->def_command2_reg = tegra_spi_readl(tspi, SPI_COMMAND2);
+ tspi->last_used_cs = master->num_chipselect + 1;
pm_runtime_put(&pdev->dev);
ret = request_threaded_irq(tspi->irq, tegra_spi_isr,
tegra_spi_isr_thread, IRQF_ONESHOT,
@@ -1451,6 +1474,8 @@ static int tegra_spi_resume(struct device *dev)
return ret;
}
tegra_spi_writel(tspi, tspi->command1_reg, SPI_COMMAND1);
+ tegra_spi_writel(tspi, tspi->def_command2_reg, SPI_COMMAND2);
+ tspi->last_used_cs = master->num_chipselect + 1;
pm_runtime_put(dev);

return spi_master_resume(master);
--
2.7.4
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