[PATCH v2 linux-next 3/3] spi: imx: Add support for SPI Slave mode
Jiada Wang
jiada_wang at mentor.com
Fri Jun 2 06:13:07 PDT 2017
Hi Sascha
On 05/31/2017 05:10 AM, Sascha Hauer wrote:
> On Wed, May 31, 2017 at 02:19:58AM -0700, jiada_wang at mentor.com wrote:
>> From: Jiada Wang <jiada_wang at mentor.com>
>>
>> Previously i.MX SPI controller only works in Master mode.
>> This patch adds support to i.MX51, i.MX53 and i.MX6 ECSPI
>> controller to work also in Slave mode.
>>
>> Currently SPI Slave mode support patch has the following limitations:
>> 1. The stale data in RXFIFO will be dropped when the Slave does any new
>> transfer.
>> 2. One transfer can be finished only after all transfer->len data been
>> transferred to master device
>> 3. Slave device only accepts transfer->len data. Any data longer than this
>> from master device will be dropped. Any data shorter than this from
>> master will cause SPI to stuck due to mentioned HW limitation 2.
>> 4. Only PIO transfer is supported in Slave mode.
>>
>> Following HW limitation applies:
>> 1. ECSPI has a HW issue when works in Slave mode, after 64
>> words written to TXFIFO, even TXFIFO becomes empty,
>> ECSPI_TXDATA keeps shift out the last word data,
>> so we have to disable ECSPI when in slave mode after the
>> transfer completes
>> 2. Due to Freescale errata ERR003775 "eCSPI: Burst completion by Chip
>> Select (SS) signal in Slave mode is not functional" burst size must
>> be set exactly to the size of the transfer. This limit SPI transaction
>> with maximum 2^12 bits. This errata affects i.MX53 and i.MX6 ECSPI
>> controllers.
>>
>> Signed-off-by: Jiada Wang <jiada_wang at mentor.com>
>> ---
>> drivers/spi/spi-imx.c | 227 +++++++++++++++++++++++++++++++++++++++++++-------
>> 1 file changed, 195 insertions(+), 32 deletions(-)
>>
>> diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
>> index 765856c..a227a30 100644
>> --- a/drivers/spi/spi-imx.c
>> +++ b/drivers/spi/spi-imx.c
>> @@ -53,9 +53,13 @@
>> /* generic defines to abstract from the different register layouts */
>> #define MXC_INT_RR (1 << 0) /* Receive data ready interrupt */
>> #define MXC_INT_TE (1 << 1) /* Transmit FIFO empty interrupt */
>> +#define MXC_INT_RDR BIT(4) /* Receive date threshold interrupt */
>>
>> /* The maximum bytes that a sdma BD can transfer.*/
>> #define MAX_SDMA_BD_BYTES (1 << 15)
>> +/* The maximum bytes that IMX53_ECSPI can transfer in slave mode.*/
>> +#define MX53_MAX_TRANSFER_BYTES 512
>> +
>> struct spi_imx_config {
>> unsigned int speed_hz;
>> unsigned int bpw;
>> @@ -79,6 +83,7 @@ struct spi_imx_devtype_data {
>> void (*trigger)(struct spi_imx_data *);
>> int (*rx_available)(struct spi_imx_data *);
>> void (*reset)(struct spi_imx_data *);
>> + void (*disable)(struct spi_imx_data *);
>> enum spi_imx_devtype devtype;
>> };
>>
>> @@ -105,6 +110,11 @@ struct spi_imx_data {
>> const void *tx_buf;
>> unsigned int txfifo; /* number of words pushed in tx FIFO */
>>
>> + /* Slave mode */
>> + bool slave_mode;
>> + bool slave_aborted;
>> + unsigned int slave_burst;
>> +
>> /* DMA */
>> bool usedma;
>> u32 wml;
>> @@ -157,6 +167,17 @@ static inline bool spi_imx_has_dmamode(struct spi_imx_data *d)
>> }
>> }
>>
>> +static inline bool spi_imx_has_slavemode(const struct spi_imx_devtype_data *d)
>> +{
>> + switch (d->devtype) {
>> + case IMX51_ECSPI:
>> + case IMX53_ECSPI:
>> + return true;
>> + default:
>> + return false;
>> + }
>> +}
> Add a new boolean flag to struct spi_imx_devtype_data instead.
>
>
>> +
>> #define MXC_SPI_BUF_RX(type) \
>> static void spi_imx_buf_rx_##type(struct spi_imx_data *spi_imx) \
>> { \
>> @@ -287,6 +308,7 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
>> #define MX51_ECSPI_INT 0x10
>> #define MX51_ECSPI_INT_TEEN (1 << 0)
>> #define MX51_ECSPI_INT_RREN (1 << 3)
>> +#define MX51_ECSPI_INT_RDREN (1 << 4)
>>
>> #define MX51_ECSPI_DMA 0x14
>> #define MX51_ECSPI_DMA_TX_WML(wml) ((wml) & 0x3f)
>> @@ -303,6 +325,51 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
>> #define MX51_ECSPI_TESTREG 0x20
>> #define MX51_ECSPI_TESTREG_LBC BIT(31)
>>
>> +static void mx53_ecspi_rx_slave(struct spi_imx_data *spi_imx)
>> +{
>> + u32 val = be32_to_cpu(readl(spi_imx->base + MXC_CSPIRXDATA));
>> +
>> + if (spi_imx->rx_buf) {
>> + int shift = spi_imx->slave_burst % sizeof(val);
>> +
>> + if (shift) {
>> + memcpy(spi_imx->rx_buf,
>> + ((u8 *)&val) + sizeof(val) - shift, shift);
>> + } else {
>> + *((u32 *)spi_imx->rx_buf) = val;
>> + shift = sizeof(val);
>> + }
>> +
>> + spi_imx->rx_buf += shift;
>> + spi_imx->slave_burst -= shift;
>> + }
>> +}
>> +
>> +static void mx53_ecspi_tx_slave(struct spi_imx_data *spi_imx)
>> +{
>> + u32 val = 0;
>> + int shift = spi_imx->count % sizeof(val);
>> +
>> + if (spi_imx->tx_buf) {
>> + if (shift) {
>> + memcpy(((u8 *)&val) + sizeof(val) - shift,
>> + spi_imx->tx_buf, shift);
>> + } else {
>> + val = *((u32 *)spi_imx->tx_buf);
>> + shift = sizeof(val);
>> + }
>> + val = cpu_to_be32(val);
>> + spi_imx->tx_buf += shift;
>> + }
>> +
>> + if (!shift)
>> + shift = sizeof(val);
> A better name for 'shift' is n_bytes. Its value should be calculated
> before the if (spi_imx->tx_buf) block. Then you can use memcpy for the
> four byte case aswell.
>
>
> But anyway, have you tested this function for anything with
> spi_imx->count % sizeof(val) != 0? In this case you have to put the fill
> the FIFO only partly somewhere. I would assume you have to do this at
> the end of the transfer, but you do this at the beginning. Can this
> work?
Yes, I have tested the case when "spi_imx->count % sizeof(val) != 0", it
works.
based on what I observed,
when the data bits written to FIFO exceeds burst len, then the 'old'
bits will be dropped.
I will update this patch set to address your review comments in v3
Thanks,
Jiada
>> +
>> + spi_imx->count -= shift;
>> +
>> + writel(val, spi_imx->base + MXC_CSPITXDATA);
>> +}
>> +
>> /* MX51 eCSPI */
>> static unsigned int mx51_ecspi_clkdiv(struct spi_imx_data *spi_imx,
>> unsigned int fspi, unsigned int *fres)
>> @@ -352,6 +419,9 @@ static void mx51_ecspi_intctrl(struct spi_imx_data *spi_imx, int enable)
>> if (enable & MXC_INT_RR)
>> val |= MX51_ECSPI_INT_RREN;
>>
>> + if (enable & MXC_INT_RDR)
>> + val |= MX51_ECSPI_INT_RDREN;
>> +
>> writel(val, spi_imx->base + MX51_ECSPI_INT);
>> }
>>
>> @@ -364,6 +434,15 @@ static void mx51_ecspi_trigger(struct spi_imx_data *spi_imx)
>> writel(reg, spi_imx->base + MX51_ECSPI_CTRL);
>> }
>>
>> +static void __maybe_unused mx51_ecspi_disable(struct spi_imx_data *spi_imx)
> I don't see how this function may end up unused.
>
>> +{
>> + u32 ctrl;
>> +
>> + ctrl = readl(spi_imx->base + MX51_ECSPI_CTRL);
>> + ctrl &= ~MX51_ECSPI_CTRL_ENABLE;
>> + writel(ctrl, spi_imx->base + MX51_ECSPI_CTRL);
>> +}
>> +
>> static int mx51_ecspi_config(struct spi_device *spi,
>> struct spi_imx_config *config)
>> {
>> @@ -372,14 +451,11 @@ static int mx51_ecspi_config(struct spi_device *spi,
>> u32 clk = config->speed_hz, delay, reg;
>> u32 cfg = readl(spi_imx->base + MX51_ECSPI_CONFIG);
>>
>> - /*
>> - * The hardware seems to have a race condition when changing modes. The
>> - * current assumption is that the selection of the channel arrives
>> - * earlier in the hardware than the mode bits when they are written at
>> - * the same time.
>> - * So set master mode for all channels as we do not support slave mode.
>> - */
>> - ctrl |= MX51_ECSPI_CTRL_MODE_MASK;
>> + /* set Master or Slave mode */
>> + if (spi_imx->slave_mode)
>> + ctrl &= ~MX51_ECSPI_CTRL_MODE_MASK;
>> + else
>> + ctrl |= MX51_ECSPI_CTRL_MODE_MASK;
>>
>> /*
>> * Enable SPI_RDY handling (falling edge/level triggered).
>> @@ -394,9 +470,21 @@ static int mx51_ecspi_config(struct spi_device *spi,
>> /* set chip select to use */
>> ctrl |= MX51_ECSPI_CTRL_CS(spi->chip_select);
>>
>> - ctrl |= (config->bpw - 1) << MX51_ECSPI_CTRL_BL_OFFSET;
>> + if (spi_imx->slave_mode && is_imx53_ecspi(spi_imx))
>> + ctrl |= (spi_imx->slave_burst * 8 - 1)
>> + << MX51_ECSPI_CTRL_BL_OFFSET;
>> + else
>> + ctrl |= (config->bpw - 1) << MX51_ECSPI_CTRL_BL_OFFSET;
>>
>> - cfg |= MX51_ECSPI_CONFIG_SBBCTRL(spi->chip_select);
>> + /*
>> + * eCSPI burst completion by Chip Select signal in Slave mode
>> + * is not functional for imx53 Soc, config SPI burst completed when
>> + * BURST_LENGTH + 1 bits are received
>> + */
>> + if (spi_imx->slave_mode && is_imx53_ecspi(spi_imx))
>> + cfg &= ~MX51_ECSPI_CONFIG_SBBCTRL(spi->chip_select);
>> + else
>> + cfg |= MX51_ECSPI_CONFIG_SBBCTRL(spi->chip_select);
>>
>> if (spi->mode & SPI_CPHA)
>> cfg |= MX51_ECSPI_CONFIG_SCLKPHA(spi->chip_select);
>> @@ -775,6 +863,7 @@ static struct spi_imx_devtype_data imx51_ecspi_devtype_data = {
>> .trigger = mx51_ecspi_trigger,
>> .rx_available = mx51_ecspi_rx_available,
>> .reset = mx51_ecspi_reset,
>> + .disable = mx51_ecspi_disable,
>> .devtype = IMX51_ECSPI,
>> };
>>
>> @@ -784,6 +873,7 @@ static struct spi_imx_devtype_data imx53_ecspi_devtype_data = {
>> .trigger = mx51_ecspi_trigger,
>> .rx_available = mx51_ecspi_rx_available,
>> .reset = mx51_ecspi_reset,
>> + .disable = mx51_ecspi_disable,
>> .devtype = IMX53_ECSPI,
>> };
>>
>> @@ -846,14 +936,16 @@ static void spi_imx_push(struct spi_imx_data *spi_imx)
>> spi_imx->txfifo++;
>> }
>>
>> - spi_imx->devtype_data->trigger(spi_imx);
>> + if (!spi_imx->slave_mode)
>> + spi_imx->devtype_data->trigger(spi_imx);
>> }
>>
>> static irqreturn_t spi_imx_isr(int irq, void *dev_id)
>> {
>> struct spi_imx_data *spi_imx = dev_id;
>>
>> - while (spi_imx->devtype_data->rx_available(spi_imx)) {
>> + while (spi_imx->txfifo &&
>> + spi_imx->devtype_data->rx_available(spi_imx)) {
>> spi_imx->rx(spi_imx);
>> spi_imx->txfifo--;
>> }
>> @@ -952,7 +1044,8 @@ static int spi_imx_setupxfer(struct spi_device *spi,
>> spi_imx->tx = spi_imx_buf_tx_u32;
>> }
>>
>> - if (spi_imx_can_dma(spi_imx->bitbang.master, spi, t))
>> + if (!spi_imx->slave_mode &&
>> + spi_imx_can_dma(spi_imx->bitbang.master, spi, t))
>> spi_imx->usedma = 1;
> So in spi_imx_can_dma() you may return true for a slave mode transfer
> and here we end up doing PIO for the same transfer. That doesn't look
> correct. You should move the test for slave mode into spi_imx_can_dma().
>
>> else
>> spi_imx->usedma = 0;
>> @@ -964,6 +1057,12 @@ static int spi_imx_setupxfer(struct spi_device *spi,
>> return ret;
>> }
>>
>> + if (is_imx53_ecspi(spi_imx) && spi_imx->slave_mode) {
>> + spi_imx->rx = mx53_ecspi_rx_slave;
>> + spi_imx->tx = mx53_ecspi_tx_slave;
>> + spi_imx->slave_burst = t->len;
>> + }
>> +
>> spi_imx->devtype_data->config(spi, &config);
>>
>> return 0;
>> @@ -1125,16 +1224,50 @@ static int spi_imx_pio_transfer(struct spi_device *spi,
>> struct spi_imx_data *spi_imx = spi_master_get_devdata(spi->master);
>> unsigned long transfer_timeout;
>> unsigned long timeout;
>> + int ret = transfer->len;
>> +
>> + if (is_imx53_ecspi(spi_imx) && spi_imx->slave_mode &&
>> + transfer->len > MX53_MAX_TRANSFER_BYTES) {
>> + pr_err("Transaction too big, max size is %d bytes\n",
>> + MX53_MAX_TRANSFER_BYTES);
> Don't use pr_* functions when you have a struct device * available.
>
>> + return -EMSGSIZE;
>> + }
>>
>> spi_imx->tx_buf = transfer->tx_buf;
>> spi_imx->rx_buf = transfer->rx_buf;
>> spi_imx->count = transfer->len;
>> spi_imx->txfifo = 0;
>>
>> + if (spi_imx->slave_mode)
>> + spi_imx->slave_burst = spi_imx->count;
> You have set this in spi_imx_setupxfer() already. Why here again?
>
>> +
>> reinit_completion(&spi_imx->xfer_done);
>> + spi_imx->slave_aborted = false;
>>
>> spi_imx_push(spi_imx);
>>
>> + if (spi_imx->slave_mode) {
>> + spi_imx->devtype_data->intctrl(spi_imx, MXC_INT_TE |
>> + MXC_INT_RDR);
>> +
>> + if (wait_for_completion_interruptible(&spi_imx->xfer_done) ||
>> + spi_imx->slave_aborted) {
>> + dev_dbg(&spi->dev, "interrupted\n");
>> + ret = -EINTR;
>> + }
>> +
>> + /* ecspi has a HW issue when works in Slave mode,
>> + * after 64 words writtern to TXFIFO, even TXFIFO becomes empty,
>> + * ECSPI_TXDATA keeps shift out the last word data,
>> + * so we have to disable ECSPI when in slave mode after the
>> + * transfer completes
>> + */
>> + if (spi_imx->devtype_data->disable)
>> + spi_imx->devtype_data->disable(spi_imx);
>> +
>> + goto out;
>> + }
>> +
>> spi_imx->devtype_data->intctrl(spi_imx, MXC_INT_TE);
>>
>> transfer_timeout = spi_imx_calculate_timeout(spi_imx, transfer->len);
> You are adding more lines to spi_imx_pio_transfer() than the original
> function had, most of them inside a if(spi_imx->slave_mode).
> It would probably more readable if you introduced a separate
> spi_imx_pio_transfer_slave().
>
> Sascha
>
>
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