diff options
| -rw-r--r-- | drivers/spi/spi-imx.c | 95 |
1 files changed, 85 insertions, 10 deletions
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c index a43b6a81d89e..0b6b0151b3a3 100644 --- a/drivers/spi/spi-imx.c +++ b/drivers/spi/spi-imx.c @@ -3,6 +3,7 @@ // Copyright (C) 2008 Juergen Beisert #include <linux/bits.h> +#include <linux/bitfield.h> #include <linux/clk.h> #include <linux/completion.h> #include <linux/delay.h> @@ -13,7 +14,10 @@ #include <linux/io.h> #include <linux/irq.h> #include <linux/kernel.h> +#include <linux/math.h> +#include <linux/math64.h> #include <linux/module.h> +#include <linux/overflow.h> #include <linux/pinctrl/consumer.h> #include <linux/platform_device.h> #include <linux/pm_runtime.h> @@ -302,6 +306,18 @@ static bool spi_imx_can_dma(struct spi_controller *controller, struct spi_device #define MX51_ECSPI_STAT 0x18 #define MX51_ECSPI_STAT_RR (1 << 3) +#define MX51_ECSPI_PERIOD 0x1c +#define MX51_ECSPI_PERIOD_MASK 0x7fff +/* + * As measured on the i.MX6, the SPI host controller inserts a 4 SPI-Clock + * (SCLK) delay after each burst if the PERIOD reg is 0x0. This value will be + * called MX51_ECSPI_PERIOD_MIN_DELAY_SCK. + * + * If the PERIOD register is != 0, the controller inserts a delay of + * MX51_ECSPI_PERIOD_MIN_DELAY_SCK + register value + 1 SCLK after each burst. + */ +#define MX51_ECSPI_PERIOD_MIN_DELAY_SCK 4 + #define MX51_ECSPI_TESTREG 0x20 #define MX51_ECSPI_TESTREG_LBC BIT(31) @@ -652,6 +668,7 @@ static int mx51_ecspi_prepare_transfer(struct spi_imx_data *spi_imx, struct spi_device *spi, struct spi_transfer *t) { u32 ctrl = readl(spi_imx->base + MX51_ECSPI_CTRL); + u64 word_delay_sck; u32 clk; /* Clear BL field and set the right value */ @@ -683,6 +700,49 @@ static int mx51_ecspi_prepare_transfer(struct spi_imx_data *spi_imx, writel(ctrl, spi_imx->base + MX51_ECSPI_CTRL); + /* calculate word delay in SPI Clock (SCLK) cycles */ + if (t->word_delay.value == 0) { + word_delay_sck = 0; + } else if (t->word_delay.unit == SPI_DELAY_UNIT_SCK) { + word_delay_sck = t->word_delay.value; + + if (word_delay_sck <= MX51_ECSPI_PERIOD_MIN_DELAY_SCK) + word_delay_sck = 0; + else if (word_delay_sck <= MX51_ECSPI_PERIOD_MIN_DELAY_SCK + 1) + word_delay_sck = 1; + else + word_delay_sck -= MX51_ECSPI_PERIOD_MIN_DELAY_SCK + 1; + } else { + int word_delay_ns; + + word_delay_ns = spi_delay_to_ns(&t->word_delay, t); + if (word_delay_ns < 0) + return word_delay_ns; + + if (word_delay_ns <= mul_u64_u32_div(NSEC_PER_SEC, + MX51_ECSPI_PERIOD_MIN_DELAY_SCK, + spi_imx->spi_bus_clk)) { + word_delay_sck = 0; + } else if (word_delay_ns <= mul_u64_u32_div(NSEC_PER_SEC, + MX51_ECSPI_PERIOD_MIN_DELAY_SCK + 1, + spi_imx->spi_bus_clk)) { + word_delay_sck = 1; + } else { + word_delay_ns -= mul_u64_u32_div(NSEC_PER_SEC, + MX51_ECSPI_PERIOD_MIN_DELAY_SCK + 1, + spi_imx->spi_bus_clk); + + word_delay_sck = DIV_U64_ROUND_UP((u64)word_delay_ns * spi_imx->spi_bus_clk, + NSEC_PER_SEC); + } + } + + if (!FIELD_FIT(MX51_ECSPI_PERIOD_MASK, word_delay_sck)) + return -EINVAL; + + writel(FIELD_PREP(MX51_ECSPI_PERIOD_MASK, word_delay_sck), + spi_imx->base + MX51_ECSPI_PERIOD); + return 0; } @@ -1263,11 +1323,13 @@ static int spi_imx_setupxfer(struct spi_device *spi, /* * Initialize the functions for transfer. To transfer non byte-aligned - * words, we have to use multiple word-size bursts, we can't use - * dynamic_burst in that case. + * words, we have to use multiple word-size bursts. To insert word + * delay, the burst size has to equal the word size. We can't use + * dynamic_burst in these cases. */ if (spi_imx->devtype_data->dynamic_burst && !spi_imx->target_mode && !(spi->mode & SPI_CS_WORD) && + !(t->word_delay.value) && (spi_imx->bits_per_word == 8 || spi_imx->bits_per_word == 16 || spi_imx->bits_per_word == 32)) { @@ -1610,12 +1672,30 @@ static int spi_imx_pio_transfer_target(struct spi_device *spi, return ret; } +static unsigned int spi_imx_transfer_estimate_time_us(struct spi_transfer *transfer) +{ + u64 result; + + result = DIV_U64_ROUND_CLOSEST((u64)USEC_PER_SEC * transfer->len * BITS_PER_BYTE, + transfer->effective_speed_hz); + if (transfer->word_delay.value) { + unsigned int word_delay_us; + unsigned int words; + + words = DIV_ROUND_UP(transfer->len * BITS_PER_BYTE, transfer->bits_per_word); + word_delay_us = DIV_ROUND_CLOSEST(spi_delay_to_ns(&transfer->word_delay, transfer), + NSEC_PER_USEC); + result += words * word_delay_us; + } + + return min(result, U32_MAX); +} + static int spi_imx_transfer_one(struct spi_controller *controller, struct spi_device *spi, struct spi_transfer *transfer) { struct spi_imx_data *spi_imx = spi_controller_get_devdata(spi->controller); - unsigned long hz_per_byte, byte_limit; spi_imx_setupxfer(spi, transfer); transfer->effective_speed_hz = spi_imx->spi_bus_clk; @@ -1634,15 +1714,10 @@ static int spi_imx_transfer_one(struct spi_controller *controller, */ if (spi_imx->usedma) return spi_imx_dma_transfer(spi_imx, transfer); - /* - * Calculate the estimated time in us the transfer runs. Find - * the number of Hz per byte per polling limit. - */ - hz_per_byte = polling_limit_us ? ((8 + 4) * USEC_PER_SEC) / polling_limit_us : 0; - byte_limit = hz_per_byte ? transfer->effective_speed_hz / hz_per_byte : 1; /* run in polling mode for short transfers */ - if (transfer->len < byte_limit) + if (transfer->len == 1 || (polling_limit_us && + spi_imx_transfer_estimate_time_us(transfer) < polling_limit_us)) return spi_imx_poll_transfer(spi, transfer); return spi_imx_pio_transfer(spi, transfer); |