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Date: Tue, 9 Jun 2015 14:24:24 +0200
From: Nicolas Ferre <nicolas.ferre@...el.com>
To: Cyrille Pitchen <cyrille.pitchen@...el.com>, <broonie@...nel.org>,
<linux-spi@...r.kernel.org>
CC: <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<devicetree@...r.kernel.org>, <robh+dt@...nel.org>,
<pawel.moll@....com>, <mark.rutland@....com>,
<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>
Subject: Re: [PATCH v3 3/3] spi: atmel: add support to FIFOs
Le 09/06/2015 13:53, Cyrille Pitchen a écrit :
> To enable the FIFO feature a "atmel,fifo-size" attribute with a strictly
> positive value must be added into the node of the device-tree describing
> the spi controller.
>
> When FIFOs are enabled, the RX one is forced to operate in SINGLE data
> mode because this driver configures the spi controller as a master. In
> master mode only, the Received Data Register has an additionnal Peripheral
> Chip Select field, which prevents us from reading more than a single data
> at each register access.
>
> Besides, the TX FIFO operates in MULTIPLE data mode. However, even when a
> 8bit data size is used, only two data by access could be written into the
> Transmit Data Register. Indeed the first data has to be written into the
> lowest 16 bits whereas the second data has to be written into the highest
> 16 bits of the TDR. When DMA transfers are used to send data, we don't
> rework the transmit buffer to cope with this hardware limitation: the
> additional copies required to prepare a new input buffer suited to both
> the DMA controller and the spi controller would waste all the benefit of
> the DMA transfer. Instead, the DMA controller is configured to write only
> one data at time into the TDR.
>
> In pio mode, two data are written in the TDR in a single access.
>
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@...el.com>
It's neat: thanks Cyrille:
Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>
> ---
> drivers/spi/spi-atmel.c | 255 ++++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 245 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
> index aa7d202..c9eca34 100644
> --- a/drivers/spi/spi-atmel.c
> +++ b/drivers/spi/spi-atmel.c
> @@ -41,6 +41,8 @@
> #define SPI_CSR1 0x0034
> #define SPI_CSR2 0x0038
> #define SPI_CSR3 0x003c
> +#define SPI_FMR 0x0040
> +#define SPI_FLR 0x0044
> #define SPI_VERSION 0x00fc
> #define SPI_RPR 0x0100
> #define SPI_RCR 0x0104
> @@ -62,6 +64,14 @@
> #define SPI_SWRST_SIZE 1
> #define SPI_LASTXFER_OFFSET 24
> #define SPI_LASTXFER_SIZE 1
> +#define SPI_TXFCLR_OFFSET 16
> +#define SPI_TXFCLR_SIZE 1
> +#define SPI_RXFCLR_OFFSET 17
> +#define SPI_RXFCLR_SIZE 1
> +#define SPI_FIFOEN_OFFSET 30
> +#define SPI_FIFOEN_SIZE 1
> +#define SPI_FIFODIS_OFFSET 31
> +#define SPI_FIFODIS_SIZE 1
>
> /* Bitfields in MR */
> #define SPI_MSTR_OFFSET 0
> @@ -114,6 +124,22 @@
> #define SPI_TXEMPTY_SIZE 1
> #define SPI_SPIENS_OFFSET 16
> #define SPI_SPIENS_SIZE 1
> +#define SPI_TXFEF_OFFSET 24
> +#define SPI_TXFEF_SIZE 1
> +#define SPI_TXFFF_OFFSET 25
> +#define SPI_TXFFF_SIZE 1
> +#define SPI_TXFTHF_OFFSET 26
> +#define SPI_TXFTHF_SIZE 1
> +#define SPI_RXFEF_OFFSET 27
> +#define SPI_RXFEF_SIZE 1
> +#define SPI_RXFFF_OFFSET 28
> +#define SPI_RXFFF_SIZE 1
> +#define SPI_RXFTHF_OFFSET 29
> +#define SPI_RXFTHF_SIZE 1
> +#define SPI_TXFPTEF_OFFSET 30
> +#define SPI_TXFPTEF_SIZE 1
> +#define SPI_RXFPTEF_OFFSET 31
> +#define SPI_RXFPTEF_SIZE 1
>
> /* Bitfields in CSR0 */
> #define SPI_CPOL_OFFSET 0
> @@ -157,6 +183,22 @@
> #define SPI_TXTDIS_OFFSET 9
> #define SPI_TXTDIS_SIZE 1
>
> +/* Bitfields in FMR */
> +#define SPI_TXRDYM_OFFSET 0
> +#define SPI_TXRDYM_SIZE 2
> +#define SPI_RXRDYM_OFFSET 4
> +#define SPI_RXRDYM_SIZE 2
> +#define SPI_TXFTHRES_OFFSET 16
> +#define SPI_TXFTHRES_SIZE 6
> +#define SPI_RXFTHRES_OFFSET 24
> +#define SPI_RXFTHRES_SIZE 6
> +
> +/* Bitfields in FLR */
> +#define SPI_TXFL_OFFSET 0
> +#define SPI_TXFL_SIZE 6
> +#define SPI_RXFL_OFFSET 16
> +#define SPI_RXFL_SIZE 6
> +
> /* Constants for BITS */
> #define SPI_BITS_8_BPT 0
> #define SPI_BITS_9_BPT 1
> @@ -167,6 +209,9 @@
> #define SPI_BITS_14_BPT 6
> #define SPI_BITS_15_BPT 7
> #define SPI_BITS_16_BPT 8
> +#define SPI_ONE_DATA 0
> +#define SPI_TWO_DATA 1
> +#define SPI_FOUR_DATA 2
>
> /* Bit manipulation macros */
> #define SPI_BIT(name) \
> @@ -185,11 +230,31 @@
> __raw_readl((port)->regs + SPI_##reg)
> #define spi_writel(port, reg, value) \
> __raw_writel((value), (port)->regs + SPI_##reg)
> +
> +#define spi_readw(port, reg) \
> + __raw_readw((port)->regs + SPI_##reg)
> +#define spi_writew(port, reg, value) \
> + __raw_writew((value), (port)->regs + SPI_##reg)
> +
> +#define spi_readb(port, reg) \
> + __raw_readb((port)->regs + SPI_##reg)
> +#define spi_writeb(port, reg, value) \
> + __raw_writeb((value), (port)->regs + SPI_##reg)
> #else
> #define spi_readl(port, reg) \
> readl_relaxed((port)->regs + SPI_##reg)
> #define spi_writel(port, reg, value) \
> writel_relaxed((value), (port)->regs + SPI_##reg)
> +
> +#define spi_readw(port, reg) \
> + readw_relaxed((port)->regs + SPI_##reg)
> +#define spi_writew(port, reg, value) \
> + writew_relaxed((value), (port)->regs + SPI_##reg)
> +
> +#define spi_readb(port, reg) \
> + readb_relaxed((port)->regs + SPI_##reg)
> +#define spi_writeb(port, reg, value) \
> + writeb_relaxed((value), (port)->regs + SPI_##reg)
> #endif
> /* use PIO for small transfers, avoiding DMA setup/teardown overhead and
> * cache operations; better heuristics consider wordsize and bitrate.
> @@ -252,6 +317,8 @@ struct atmel_spi {
>
> bool keep_cs;
> bool cs_active;
> +
> + u32 fifo_size;
> };
>
> /* Controller-specific per-slave state */
> @@ -410,6 +477,20 @@ static int atmel_spi_dma_slave_config(struct atmel_spi *as,
> slave_config->dst_maxburst = 1;
> slave_config->device_fc = false;
>
> + /*
> + * This driver uses fixed peripheral select mode (PS bit set to '0' in
> + * the Mode Register).
> + * So according to the datasheet, when FIFOs are available (and
> + * enabled), the Transmit FIFO operates in Multiple Data Mode.
> + * In this mode, up to 2 data, not 4, can be written into the Transmit
> + * Data Register in a single access.
> + * However, the first data has to be written into the lowest 16 bits and
> + * the second data into the highest 16 bits of the Transmit
> + * Data Register. For 8bit data (the most frequent case), it would
> + * require to rework tx_buf so each data would actualy fit 16 bits.
> + * So we'd rather write only one data at the time. Hence the transmit
> + * path works the same whether FIFOs are available (and enabled) or not.
> + */
> slave_config->direction = DMA_MEM_TO_DEV;
> if (dmaengine_slave_config(as->dma.chan_tx, slave_config)) {
> dev_err(&as->pdev->dev,
> @@ -417,6 +498,14 @@ static int atmel_spi_dma_slave_config(struct atmel_spi *as,
> err = -EINVAL;
> }
>
> + /*
> + * This driver configures the spi controller for master mode (MSTR bit
> + * set to '1' in the Mode Register).
> + * So according to the datasheet, when FIFOs are available (and
> + * enabled), the Receive FIFO operates in Single Data Mode.
> + * So the receive path works the same whether FIFOs are available (and
> + * enabled) or not.
> + */
> slave_config->direction = DMA_DEV_TO_MEM;
> if (dmaengine_slave_config(as->dma.chan_rx, slave_config)) {
> dev_err(&as->pdev->dev,
> @@ -506,10 +595,10 @@ static void dma_callback(void *data)
> }
>
> /*
> - * Next transfer using PIO.
> + * Next transfer using PIO without FIFO.
> */
> -static void atmel_spi_next_xfer_pio(struct spi_master *master,
> - struct spi_transfer *xfer)
> +static void atmel_spi_next_xfer_single(struct spi_master *master,
> + struct spi_transfer *xfer)
> {
> struct atmel_spi *as = spi_master_get_devdata(master);
> unsigned long xfer_pos = xfer->len - as->current_remaining_bytes;
> @@ -542,6 +631,99 @@ static void atmel_spi_next_xfer_pio(struct spi_master *master,
> }
>
> /*
> + * Next transfer using PIO with FIFO.
> + */
> +static void atmel_spi_next_xfer_fifo(struct spi_master *master,
> + struct spi_transfer *xfer)
> +{
> + struct atmel_spi *as = spi_master_get_devdata(master);
> + u32 current_remaining_data, num_data;
> + u32 offset = xfer->len - as->current_remaining_bytes;
> + const u16 *words = (const u16 *)((u8 *)xfer->tx_buf + offset);
> + const u8 *bytes = (const u8 *)((u8 *)xfer->tx_buf + offset);
> + u16 td0, td1;
> + u32 fifomr;
> +
> + dev_vdbg(master->dev.parent, "atmel_spi_next_xfer_fifo\n");
> +
> + /* Compute the number of data to transfer in the current iteration */
> + current_remaining_data = ((xfer->bits_per_word > 8) ?
> + ((u32)as->current_remaining_bytes >> 1) :
> + (u32)as->current_remaining_bytes);
> + num_data = min(current_remaining_data, as->fifo_size);
> +
> + /* Flush RX and TX FIFOs */
> + spi_writel(as, CR, SPI_BIT(RXFCLR) | SPI_BIT(TXFCLR));
> + while (spi_readl(as, FLR))
> + cpu_relax();
> +
> + /* Set RX FIFO Threshold to the number of data to transfer */
> + fifomr = spi_readl(as, FMR);
> + spi_writel(as, FMR, SPI_BFINS(RXFTHRES, num_data, fifomr));
> +
> + /* Clear FIFO flags in the Status Register, especially RXFTHF */
> + (void)spi_readl(as, SR);
> +
> + /* Fill TX FIFO */
> + while (num_data >= 2) {
> + if (xfer->tx_buf) {
> + if (xfer->bits_per_word > 8) {
> + td0 = *words++;
> + td1 = *words++;
> + } else {
> + td0 = *bytes++;
> + td1 = *bytes++;
> + }
> + } else {
> + td0 = 0;
> + td1 = 0;
> + }
> +
> + spi_writel(as, TDR, (td1 << 16) | td0);
> + num_data -= 2;
> + }
> +
> + if (num_data) {
> + if (xfer->tx_buf) {
> + if (xfer->bits_per_word > 8)
> + td0 = *words++;
> + else
> + td0 = *bytes++;
> + } else {
> + td0 = 0;
> + }
> +
> + spi_writew(as, TDR, td0);
> + num_data--;
> + }
> +
> + dev_dbg(master->dev.parent,
> + " start fifo xfer %p: len %u tx %p rx %p bitpw %d\n",
> + xfer, xfer->len, xfer->tx_buf, xfer->rx_buf,
> + xfer->bits_per_word);
> +
> + /*
> + * Enable RX FIFO Threshold Flag interrupt to be notified about
> + * transfer completion.
> + */
> + spi_writel(as, IER, SPI_BIT(RXFTHF) | SPI_BIT(OVRES));
> +}
> +
> +/*
> + * Next transfer using PIO.
> + */
> +static void atmel_spi_next_xfer_pio(struct spi_master *master,
> + struct spi_transfer *xfer)
> +{
> + struct atmel_spi *as = spi_master_get_devdata(master);
> +
> + if (as->fifo_size)
> + atmel_spi_next_xfer_fifo(master, xfer);
> + else
> + atmel_spi_next_xfer_single(master, xfer);
> +}
> +
> +/*
> * Submit next transfer for DMA.
> */
> static int atmel_spi_next_xfer_dma_submit(struct spi_master *master,
> @@ -843,13 +1025,8 @@ static void atmel_spi_disable_pdc_transfer(struct atmel_spi *as)
> spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));
> }
>
> -/* Called from IRQ
> - *
> - * Must update "current_remaining_bytes" to keep track of data
> - * to transfer.
> - */
> static void
> -atmel_spi_pump_pio_data(struct atmel_spi *as, struct spi_transfer *xfer)
> +atmel_spi_pump_single_data(struct atmel_spi *as, struct spi_transfer *xfer)
> {
> u8 *rxp;
> u16 *rxp16;
> @@ -876,6 +1053,57 @@ atmel_spi_pump_pio_data(struct atmel_spi *as, struct spi_transfer *xfer)
> }
> }
>
> +static void
> +atmel_spi_pump_fifo_data(struct atmel_spi *as, struct spi_transfer *xfer)
> +{
> + u32 fifolr = spi_readl(as, FLR);
> + u32 num_bytes, num_data = SPI_BFEXT(RXFL, fifolr);
> + u32 offset = xfer->len - as->current_remaining_bytes;
> + u16 *words = (u16 *)((u8 *)xfer->rx_buf + offset);
> + u8 *bytes = (u8 *)((u8 *)xfer->rx_buf + offset);
> + u16 rd; /* RD field is the lowest 16 bits of RDR */
> +
> + /* Update the number of remaining bytes to transfer */
> + num_bytes = ((xfer->bits_per_word > 8) ?
> + (num_data << 1) :
> + num_data);
> +
> + if (as->current_remaining_bytes > num_bytes)
> + as->current_remaining_bytes -= num_bytes;
> + else
> + as->current_remaining_bytes = 0;
> +
> + /* Handle odd number of bytes when data are more than 8bit width */
> + if (xfer->bits_per_word > 8)
> + as->current_remaining_bytes &= ~0x1;
> +
> + /* Read data */
> + while (num_data) {
> + rd = spi_readl(as, RDR);
> + if (xfer->rx_buf) {
> + if (xfer->bits_per_word > 8)
> + *words++ = rd;
> + else
> + *bytes++ = rd;
> + }
> + num_data--;
> + }
> +}
> +
> +/* Called from IRQ
> + *
> + * Must update "current_remaining_bytes" to keep track of data
> + * to transfer.
> + */
> +static void
> +atmel_spi_pump_pio_data(struct atmel_spi *as, struct spi_transfer *xfer)
> +{
> + if (as->fifo_size)
> + atmel_spi_pump_fifo_data(as, xfer);
> + else
> + atmel_spi_pump_single_data(as, xfer);
> +}
> +
> /* Interrupt
> *
> * No need for locking in this Interrupt handler: done_status is the
> @@ -916,7 +1144,7 @@ atmel_spi_pio_interrupt(int irq, void *dev_id)
>
> complete(&as->xfer_completion);
>
> - } else if (pending & SPI_BIT(RDRF)) {
> + } else if (pending & (SPI_BIT(RDRF) | SPI_BIT(RXFTHF))) {
> atmel_spi_lock(as);
>
> if (as->current_remaining_bytes) {
> @@ -1399,6 +1627,13 @@ static int atmel_spi_probe(struct platform_device *pdev)
> spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));
> spi_writel(as, CR, SPI_BIT(SPIEN));
>
> + as->fifo_size = 0;
> + if (!of_property_read_u32(pdev->dev.of_node, "atmel,fifo-size",
> + &as->fifo_size)) {
> + dev_info(&pdev->dev, "Using FIFO (%u data)\n", as->fifo_size);
> + spi_writel(as, CR, SPI_BIT(FIFOEN));
> + }
> +
> /* go! */
> dev_info(&pdev->dev, "Atmel SPI Controller at 0x%08lx (irq %d)\n",
> (unsigned long)regs->start, irq);
>
--
Nicolas Ferre
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