Hi Daniil
On 5/24/21 12:24 AM, Daniil Stas wrote:
> 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.s...@posteo.net>
> Cc: Patrick Delaunay <patrick.delau...@foss.st.com>
> Cc: Patrice Chotard <patrice.chot...@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;
> }
>
Have you got a simple test to reproduce the described race condition ?
Thanks
Patrice
