TCF flag only means that all data was sent to FIFO. To check if the data was sent out of FIFO we should also wait for the BUSY flag to be cleared. Otherwise there is a race condition which can lead to inability to write short (one byte long) data.
Signed-off-by: Daniil Stas daniil.stas@posteo.net Cc: Patrick Delaunay patrick.delaunay@foss.st.com Cc: Patrice Chotard patrice.chotard@foss.st.com --- drivers/spi/stm32_qspi.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-)
diff --git a/drivers/spi/stm32_qspi.c b/drivers/spi/stm32_qspi.c index 4acc9047b9..8f4aabc3d1 100644 --- a/drivers/spi/stm32_qspi.c +++ b/drivers/spi/stm32_qspi.c @@ -148,23 +148,24 @@ static int _stm32_qspi_wait_cmd(struct stm32_qspi_priv *priv, const struct spi_mem_op *op) { u32 sr; - int ret; - - if (!op->data.nbytes) - return _stm32_qspi_wait_for_not_busy(priv); + int ret = 0;
- ret = readl_poll_timeout(&priv->regs->sr, sr, - sr & STM32_QSPI_SR_TCF, - STM32_QSPI_CMD_TIMEOUT_US); - if (ret) { - log_err("cmd timeout (stat:%#x)\n", sr); - } else if (readl(&priv->regs->sr) & STM32_QSPI_SR_TEF) { - log_err("transfer error (stat:%#x)\n", sr); - ret = -EIO; + if (op->data.nbytes) { + ret = readl_poll_timeout(&priv->regs->sr, sr, + sr & STM32_QSPI_SR_TCF, + STM32_QSPI_CMD_TIMEOUT_US); + if (ret) { + log_err("cmd timeout (stat:%#x)\n", sr); + } else if (readl(&priv->regs->sr) & STM32_QSPI_SR_TEF) { + log_err("transfer error (stat:%#x)\n", sr); + ret = -EIO; + } + /* clear flags */ + writel(STM32_QSPI_FCR_CTCF | STM32_QSPI_FCR_CTEF, &priv->regs->fcr); }
- /* clear flags */ - writel(STM32_QSPI_FCR_CTCF | STM32_QSPI_FCR_CTEF, &priv->regs->fcr); + if (!ret) + ret = _stm32_qspi_wait_for_not_busy(priv);
return ret; }