[PATCH v2] spi: mediatek: Don't modify spi_transfer when transfer.

[Peter Shih]

Mediatek SPI driver modifies some fields (tx_buf, rx_buf, len, tx_dma,
rx_dma) of the spi_transfer* passed in when doing transfer_one and in
interrupt handler. This is somewhat unexpected, and there are some
caller (e.g. Cr50 spi driver) that reuse the spi_transfer for multiple
messages. Add a field to record how many bytes have been transferred,
and calculate the right len / buffer based on it instead.

Signed-off-by: Pi-Hsun Shih <pih...@chromium.org>

Change-Id: I23e218cd964f16c0b2b26127d4a5ca6529867673
---
 drivers/spi/spi-mt65xx.c | 37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/drivers/spi/spi-mt65xx.c b/drivers/spi/spi-mt65xx.c
index 86bf45667a040..3dc31627c6558 100644
--- a/drivers/spi/spi-mt65xx.c
+++ b/drivers/spi/spi-mt65xx.c
@@ -98,6 +98,7 @@ struct mtk_spi {
        struct clk *parent_clk, *sel_clk, *spi_clk;
        struct spi_transfer *cur_transfer;
        u32 xfer_len;
+       u32 num_xfered;
        struct scatterlist *tx_sgl, *rx_sgl;
        u32 tx_sgl_len, rx_sgl_len;
        const struct mtk_spi_compatible *dev_comp;
@@ -385,6 +386,7 @@ static int mtk_spi_fifo_transfer(struct spi_master *master,
 
        mdata->cur_transfer = xfer;
        mdata->xfer_len = min(MTK_SPI_MAX_FIFO_SIZE, xfer->len);
+       mdata->num_xfered = 0;
        mtk_spi_prepare_transfer(master, xfer);
        mtk_spi_setup_packet(master);
 
@@ -415,6 +417,7 @@ static int mtk_spi_dma_transfer(struct spi_master *master,
        mdata->tx_sgl_len = 0;
        mdata->rx_sgl_len = 0;
        mdata->cur_transfer = xfer;
+       mdata->num_xfered = 0;
 
        mtk_spi_prepare_transfer(master, xfer);
 
@@ -482,7 +485,7 @@ static int mtk_spi_setup(struct spi_device *spi)
 
 static irqreturn_t mtk_spi_interrupt(int irq, void *dev_id)
 {
-       u32 cmd, reg_val, cnt, remainder;
+       u32 cmd, reg_val, cnt, remainder, len;
        struct spi_master *master = dev_id;
        struct mtk_spi *mdata = spi_master_get_devdata(master);
        struct spi_transfer *trans = mdata->cur_transfer;
@@ -497,36 +500,38 @@ static irqreturn_t mtk_spi_interrupt(int irq, void 
*dev_id)
                if (trans->rx_buf) {
                        cnt = mdata->xfer_len / 4;
                        ioread32_rep(mdata->base + SPI_RX_DATA_REG,
-                                    trans->rx_buf, cnt);
+                                    trans->rx_buf + mdata->num_xfered, cnt);
                        remainder = mdata->xfer_len % 4;
                        if (remainder > 0) {
                                reg_val = readl(mdata->base + SPI_RX_DATA_REG);
-                               memcpy(trans->rx_buf + (cnt * 4),
-                                       &reg_val, remainder);
+                               memcpy(trans->rx_buf +
+                                       mdata->num_xfered +
+                                       (cnt * 4),
+                                       &reg_val,
+                                       remainder);
                        }
                }
 
-               trans->len -= mdata->xfer_len;
-               if (!trans->len) {
+               mdata->num_xfered += mdata->xfer_len;
+               if (mdata->num_xfered == trans->len) {
                        spi_finalize_current_transfer(master);
                        return IRQ_HANDLED;
                }
 
-               if (trans->tx_buf)
-                       trans->tx_buf += mdata->xfer_len;
-               if (trans->rx_buf)
-                       trans->rx_buf += mdata->xfer_len;
-
-               mdata->xfer_len = min(MTK_SPI_MAX_FIFO_SIZE, trans->len);
+               len = trans->len - mdata->num_xfered;
+               mdata->xfer_len = min(MTK_SPI_MAX_FIFO_SIZE, len);
                mtk_spi_setup_packet(master);
 
-               cnt = trans->len / 4;
-               iowrite32_rep(mdata->base + SPI_TX_DATA_REG, trans->tx_buf, 
cnt);
+               cnt = len / 4;
+               iowrite32_rep(mdata->base + SPI_TX_DATA_REG,
+                               trans->tx_buf + mdata->num_xfered, cnt);
 
-               remainder = trans->len % 4;
+               remainder = len % 4;
                if (remainder > 0) {
                        reg_val = 0;
-                       memcpy(&reg_val, trans->tx_buf + (cnt * 4), remainder);
+                       memcpy(&reg_val,
+                               trans->tx_buf + (cnt * 4) + mdata->num_xfered,
+                               remainder);
                        writel(reg_val, mdata->base + SPI_TX_DATA_REG);
                }
 
-- 
2.19.0.rc2.392.g5ba43deb5a-goog