MX28: SPI: Supercharge the SPI driver

This change implements DMA chaining into SPI driver. This allows
the transfers to go much faster, while also fixing SF issues.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Stefano Babic <sbabic@denx.de>

diff --git a/drivers/spi/mxs_spi.c b/drivers/spi/mxs_spi.c
index 5fa7f2b73c52b22e26919714dd66fcda8495639c..168dbe497e6dc73f70cdd38a3c98030e32b6dbe8 100644 (file)
--- a/drivers/spi/mxs_spi.c
+++ b/drivers/spi/mxs_spi.c
@@ -56,7 +56,6 @@ struct mxs_spi_slave {
        uint32_t                max_khz;
        uint32_t                mode;
        struct mxs_ssp_regs     *regs;
-       struct mxs_dma_desc     *desc;
 };
 
 static inline struct mxs_spi_slave *to_mxs_slave(struct spi_slave *slave)
@@ -84,7 +83,6 @@ struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
        uint32_t addr;
        struct mxs_ssp_regs *ssp_regs;
        int reg;
-       struct mxs_dma_desc *desc;
 
        if (!spi_cs_is_valid(bus, cs)) {
                printf("mxs_spi: invalid bus %d / chip select %d\n", bus, cs);
@@ -95,10 +93,6 @@ struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
        if (!mxs_slave)
                return NULL;
 
-       desc = mxs_dma_desc_alloc();
-       if (!desc)
-               goto err_desc;
-
        if (mxs_dma_init_channel(bus))
                goto err_init;
 
@@ -109,7 +103,6 @@ struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
        mxs_slave->max_khz = max_hz / 1000;
        mxs_slave->mode = mode;
        mxs_slave->regs = (struct mxs_ssp_regs *)addr;
-       mxs_slave->desc = desc;
        ssp_regs = mxs_slave->regs;
 
        reg = readl(&ssp_regs->hw_ssp_ctrl0);
@@ -120,8 +113,6 @@ struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
        return &mxs_slave->slave;
 
 err_init:
-       mxs_dma_desc_free(desc);
-err_desc:
        free(mxs_slave);
        return NULL;
 }
@@ -129,7 +120,6 @@ err_desc:
 void spi_free_slave(struct spi_slave *slave)
 {
        struct mxs_spi_slave *mxs_slave = to_mxs_slave(slave);
-       mxs_dma_desc_free(mxs_slave->desc);
        free(mxs_slave);
 }
 
@@ -228,19 +218,24 @@ static int mxs_spi_xfer_pio(struct mxs_spi_slave *slave,
 static int mxs_spi_xfer_dma(struct mxs_spi_slave *slave,
                        char *data, int length, int write, unsigned long flags)
 {
-       struct mxs_dma_desc *desc = slave->desc;
+       const int xfer_max_sz = 0xff00;
+       const int desc_count = DIV_ROUND_UP(length, xfer_max_sz) + 1;
        struct mxs_ssp_regs *ssp_regs = slave->regs;
-       uint32_t ctrl0 = SSP_CTRL0_DATA_XFER;
+       struct mxs_dma_desc *dp;
+       uint32_t ctrl0;
        uint32_t cache_data_count;
        int dmach;
+       int tl;
+
+       ALLOC_CACHE_ALIGN_BUFFER(struct mxs_dma_desc, desc, desc_count);
+
+       memset(desc, 0, sizeof(struct mxs_dma_desc) * desc_count);
 
-       memset(desc, 0, sizeof(struct mxs_dma_desc));
-       desc->address = (dma_addr_t)desc;
+       ctrl0 = readl(&ssp_regs->hw_ssp_ctrl0);
+       ctrl0 |= SSP_CTRL0_DATA_XFER;
 
        if (flags & SPI_XFER_BEGIN)
                ctrl0 |= SSP_CTRL0_LOCK_CS;
-       if (flags & SPI_XFER_END)
-               ctrl0 |= SSP_CTRL0_IGNORE_CRC;
        if (!write)
                ctrl0 |= SSP_CTRL0_READ;
 
@@ -251,27 +246,66 @@ static int mxs_spi_xfer_dma(struct mxs_spi_slave *slave,
        else
                cache_data_count = length;
 
-       if (!write) {
-               slave->desc->cmd.data = MXS_DMA_DESC_COMMAND_DMA_WRITE;
-               slave->desc->cmd.address = (dma_addr_t)data;
-       } else {
-               slave->desc->cmd.data = MXS_DMA_DESC_COMMAND_DMA_READ;
-               slave->desc->cmd.address = (dma_addr_t)data;
-
+       if (write)
                /* Flush data to DRAM so DMA can pick them up */
                flush_dcache_range((uint32_t)data,
                        (uint32_t)(data + cache_data_count));
-       }
 
-       slave->desc->cmd.data |= MXS_DMA_DESC_IRQ | MXS_DMA_DESC_DEC_SEM |
-                               (length << MXS_DMA_DESC_BYTES_OFFSET) |
-                               (1 << MXS_DMA_DESC_PIO_WORDS_OFFSET) |
-                               MXS_DMA_DESC_WAIT4END;
+       dmach = MXS_DMA_CHANNEL_AHB_APBH_SSP0 + slave->slave.bus;
 
-       slave->desc->cmd.pio_words[0] = ctrl0;
+       dp = desc;
+       while (length) {
+               dp->address = (dma_addr_t)dp;
+               dp->cmd.address = (dma_addr_t)data;
+
+               /*
+                * This is correct, even though it does indeed look insane.
+                * I hereby have to, wholeheartedly, thank Freescale Inc.,
+                * for always inventing insane hardware and keeping me busy
+                * and employed ;-)
+                */
+               if (write)
+                       dp->cmd.data = MXS_DMA_DESC_COMMAND_DMA_READ;
+               else
+                       dp->cmd.data = MXS_DMA_DESC_COMMAND_DMA_WRITE;
+
+               /*
+                * The DMA controller can transfer large chunks (64kB) at
+                * time by setting the transfer length to 0. Setting tl to
+                * 0x10000 will overflow below and make .data contain 0.
+                * Otherwise, 0xff00 is the transfer maximum.
+                */
+               if (length >= 0x10000)
+                       tl = 0x10000;
+               else
+                       tl = min(length, xfer_max_sz);
+
+               dp->cmd.data |=
+                       (tl << MXS_DMA_DESC_BYTES_OFFSET) |
+                       (1 << MXS_DMA_DESC_PIO_WORDS_OFFSET) |
+                       MXS_DMA_DESC_HALT_ON_TERMINATE |
+                       MXS_DMA_DESC_TERMINATE_FLUSH;
+               dp->cmd.pio_words[0] = ctrl0;
+
+               data += tl;
+               length -= tl;
+
+               mxs_dma_desc_append(dmach, dp);
+
+               dp++;
+       }
+
+       dp->address = (dma_addr_t)dp;
+       dp->cmd.address = (dma_addr_t)0;
+       dp->cmd.data = MXS_DMA_DESC_COMMAND_NO_DMAXFER |
+                       (1 << MXS_DMA_DESC_PIO_WORDS_OFFSET) |
+                       MXS_DMA_DESC_IRQ | MXS_DMA_DESC_DEC_SEM;
+       if (flags & SPI_XFER_END) {
+               ctrl0 &= ~SSP_CTRL0_LOCK_CS;
+               dp->cmd.pio_words[0] = ctrl0 | SSP_CTRL0_IGNORE_CRC;
+       }
+       mxs_dma_desc_append(dmach, dp);
 
-       dmach = MXS_DMA_CHANNEL_AHB_APBH_SSP0 + slave->slave.bus;
-       mxs_dma_desc_append(dmach, slave->desc);
        if (mxs_dma_go(dmach))
                return -EINVAL;