[PATCH] spi: mediatek: Fix fifo transfer
Guenter Roeck
linux at roeck-us.net
Mon Aug 2 06:57:40 PDT 2021
On 8/1/21 8:00 PM, Guenter Roeck wrote:
> Commit 3a70dd2d0503 ("spi: mediatek: fix fifo rx mode") claims that
> fifo RX mode was never handled, and adds the presumably missing code
> to the FIFO transfer function. However, the claim that receive data
> was not handled is incorrect. It was handled as part of interrupt
> handling after the transfer was complete. The code added with the above
> mentioned commit reads data from the receive FIFO before the transfer
> is started, which is wrong. This results in an actual transfer error
> on a Hayato Chromebook.
>
> Remove the code trying to handle receive data before the transfer is
> started to fix the problem.
>
> Fixes: 3a70dd2d0503 ("spi: mediatek: fix fifo rx mode")
> Cc: Peter Hess <peter.hess at ph-home.de>
> Cc: Frank Wunderlich <frank-w at public-files.de>
> Cc: Tzung-Bi Shih <tzungbi at google.com>
> Cc: Hsin-Yi Wang <hsinyi at google.com>
> Signed-off-by: Guenter Roeck <linux at roeck-us.net>
> ---
I should have added here: If this patch isn't acceptable for some reason,
commit 3a70dd2d0503 should be reverted because it is obviously wrong
and introduces a severe regression.
Thanks,
Guenter
> drivers/spi/spi-mt65xx.c | 19 +++++--------------
> 1 file changed, 5 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/spi/spi-mt65xx.c b/drivers/spi/spi-mt65xx.c
> index 68dca8ceb3ad..7914255521c3 100644
> --- a/drivers/spi/spi-mt65xx.c
> +++ b/drivers/spi/spi-mt65xx.c
> @@ -426,24 +426,15 @@ static int mtk_spi_fifo_transfer(struct spi_master *master,
> mtk_spi_prepare_transfer(master, xfer);
> mtk_spi_setup_packet(master);
>
> - cnt = xfer->len / 4;
> - if (xfer->tx_buf)
> + if (xfer->tx_buf) {
> + cnt = xfer->len / 4;
> iowrite32_rep(mdata->base + SPI_TX_DATA_REG, xfer->tx_buf, cnt);
> -
> - if (xfer->rx_buf)
> - ioread32_rep(mdata->base + SPI_RX_DATA_REG, xfer->rx_buf, cnt);
> -
> - remainder = xfer->len % 4;
> - if (remainder > 0) {
> - reg_val = 0;
> - if (xfer->tx_buf) {
> + remainder = xfer->len % 4;
> + if (remainder > 0) {
> + reg_val = 0;
> memcpy(®_val, xfer->tx_buf + (cnt * 4), remainder);
> writel(reg_val, mdata->base + SPI_TX_DATA_REG);
> }
> - if (xfer->rx_buf) {
> - reg_val = readl(mdata->base + SPI_RX_DATA_REG);
> - memcpy(xfer->rx_buf + (cnt * 4), ®_val, remainder);
> - }
> }
>
> mtk_spi_enable_transfer(master);
>
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