greybus: spi: fix transfers bigger than greybus payload

Add helper functions calculate the tx and rx size possible that fit a
greybus payload size and change the operation creation to adjust to that.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

diff --git a/drivers/staging/greybus/spi.c b/drivers/staging/greybus/spi.c
index 8e0e403..094d6d8 100644 (file)
--- a/drivers/staging/greybus/spi.c
+++ b/drivers/staging/greybus/spi.c
@@ -31,6 +31,51 @@ static struct spi_master *get_master_from_spi(struct gb_spi *spi)
        return spi->connection->private;
 }
 
+static int tx_header_fit_operation(u32 tx_size, u32 count, size_t data_max)
+{
+       size_t headers_size;
+
+       data_max -= sizeof(struct gb_spi_transfer_request);
+       headers_size = (count + 1) * sizeof(struct gb_spi_transfer);
+
+       return tx_size + headers_size > data_max ? 0 : 1;
+}
+
+static size_t calc_rx_xfer_size(u32 rx_size, u32 *tx_xfer_size, u32 len,
+                               size_t data_max)
+{
+       size_t rx_xfer_size;
+
+       data_max -= sizeof(struct gb_spi_transfer_response);
+
+       if (rx_size + len > data_max)
+               rx_xfer_size = data_max - rx_size;
+       else
+               rx_xfer_size = len;
+
+       /* if this is a write_read, for symmetry read the same as write */
+       if (*tx_xfer_size && rx_xfer_size > *tx_xfer_size)
+               rx_xfer_size = *tx_xfer_size;
+       if (*tx_xfer_size && rx_xfer_size < *tx_xfer_size)
+               *tx_xfer_size = rx_xfer_size;
+
+       return rx_xfer_size;
+}
+
+static size_t calc_tx_xfer_size(u32 tx_size, u32 count, size_t len,
+                               size_t data_max)
+{
+       size_t headers_size;
+
+       data_max -= sizeof(struct gb_spi_transfer_request);
+       headers_size = (count + 1) * sizeof(struct gb_spi_transfer);
+
+       if (tx_size + headers_size + len > data_max)
+               return data_max - (tx_size + sizeof(struct gb_spi_transfer));
+
+       return len;
+}
+
 /* Routines to transfer data */
 static struct gb_operation *
 gb_spi_operation_create(struct gb_connection *connection,
@@ -41,9 +86,14 @@ gb_spi_operation_create(struct gb_connection *connection,
        struct spi_transfer *xfer;
        struct gb_spi_transfer *gb_xfer;
        struct gb_operation *operation;
-       u32 tx_size = 0, rx_size = 0, count = 0, request_size;
+       struct spi_transfer *last_xfer = NULL;
+       u32 tx_size = 0, rx_size = 0, count = 0, xfer_len = 0, request_size;
+       u32 tx_xfer_size = 0, rx_xfer_size = 0, last_xfer_size = 0;
+       size_t data_max;
        void *tx_data;
 
+       data_max = gb_operation_get_payload_size_max(connection);
+
        /* Find number of transfers queued and tx/rx length in the message */
        list_for_each_entry(xfer, &msg->transfers, transfer_list) {
                if (!xfer->tx_buf && !xfer->rx_buf) {
@@ -51,21 +101,33 @@ gb_spi_operation_create(struct gb_connection *connection,
                                "bufferless transfer, length %u\n", xfer->len);
                        return NULL;
                }
+               last_xfer = xfer;
 
-               if (xfer->tx_buf)
-                       tx_size += xfer->len;
-               if (xfer->rx_buf)
-                       rx_size += xfer->len;
+               tx_xfer_size = 0;
+               rx_xfer_size = 0;
+
+               if (xfer->tx_buf) {
+                       if (!tx_header_fit_operation(tx_size, count, data_max))
+                               break;
+                       tx_xfer_size = calc_tx_xfer_size(tx_size, count,
+                                                        xfer->len, data_max);
+                       last_xfer_size = tx_xfer_size;
+               }
+
+               if (xfer->rx_buf) {
+                       rx_xfer_size = calc_rx_xfer_size(rx_size, &tx_xfer_size,
+                                                        xfer->len, data_max);
+                       last_xfer_size = rx_xfer_size;
+               }
+
+               tx_size += tx_xfer_size;
+               rx_size += rx_xfer_size;
 
-               *total_len += xfer->len;
+               *total_len += last_xfer_size;
                count++;
-       }
 
-       /* Too many transfers ? */
-       if (count > (u32)U16_MAX) {
-               dev_err(&connection->bundle->dev,
-                       "transfer count (%u) too big\n", count);
-               return NULL;
+               if (xfer->len != last_xfer_size)
+                       break;
        }
 
        /*
@@ -92,20 +154,30 @@ gb_spi_operation_create(struct gb_connection *connection,
 
        /* Fill in the transfers array */
        list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+               if (last_xfer && xfer == last_xfer)
+                       xfer_len = last_xfer_size;
+               else
+                       xfer_len = xfer->len;
+
                gb_xfer->speed_hz = cpu_to_le32(xfer->speed_hz);
-               gb_xfer->len = cpu_to_le32(xfer->len);
+               gb_xfer->len = cpu_to_le32(xfer_len);
                gb_xfer->delay_usecs = cpu_to_le16(xfer->delay_usecs);
                gb_xfer->cs_change = xfer->cs_change;
                gb_xfer->bits_per_word = xfer->bits_per_word;
 
                /* Copy tx data */
                if (xfer->tx_buf) {
-                       memcpy(tx_data, xfer->tx_buf, xfer->len);
-                       tx_data += xfer->len;
                        gb_xfer->rdwr |= GB_SPI_XFER_WRITE;
+                       memcpy(tx_data, xfer->tx_buf, xfer_len);
+                       tx_data += xfer_len;
                }
+
                if (xfer->rx_buf)
                        gb_xfer->rdwr |= GB_SPI_XFER_READ;
+
+               if (last_xfer && xfer == last_xfer)
+                       break;
+
                gb_xfer++;
        }