stm32: Revert "stm32: performance improvement for spi on stm32f0"

This reverts commit a2c309a2b02d16ec15fee5702463621239261266.

The above commit is causing crashes on the stm32f103xb chip when spi
is in use.  It's unclear what the cause of the regression is, but the
optimization isn't required so revert it until the root cause can be
determined.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 4 insertions, 8 deletions

diff --git a/src/stm32/spi.c b/src/stm32/spi.c
index 90d71ffe..5e306fd1 100644
--- a/src/stm32/spi.c
+++ b/src/stm32/spi.c
@@ -92,14 +92,10 @@ spi_transfer(struct spi_config config, uint8_t receive_data,
              uint8_t len, uint8_t *data)
 {
     SPI_TypeDef *spi = config.spi;
-    uint8_t *wptr = data;
-    uint8_t *end = data + len;
-
-    while (data < end) {
-        if (spi->SR & SPI_SR_TXE && wptr < end)
-            writeb((void *)&spi->DR, *wptr++);
-        if (!(spi->SR & SPI_SR_RXNE))
-            continue;
+    while (len--) {
+        writeb((void *)&spi->DR, *data);
+        while (!(spi->SR & SPI_SR_RXNE))
+            ;
         uint8_t rdata = readb((void *)&spi->DR);
         if (receive_data)
             *data = rdata;