From: Sean Anderson Date: Fri, 16 Oct 2020 22:57:43 +0000 (-0400) Subject: spi: dw: Fix driving MOSI low while recieving X-Git-Url: http://git.dujemihanovic.xyz/login.html?a=commitdiff_plain;h=caf110798ccca5d1fe7e75ae73397212262b9ee9;p=u-boot.git spi: dw: Fix driving MOSI low while recieving The resting state of MOSI is high when nothing is driving it. If we drive it low while recieving, it looks like we are transmitting 0x00 instead of transmitting nothing. This can confuse slaves (like SD cards) which allow new commands to be sent over MOSI while they are returning data over MISO. The return of MOSI from 0 to 1 at the end of recieving a byte can look like a start bit and a transmission bit to an SD card. This will cause the card to become out-of-sync with the SPI device, as it thinks the device has already started transmitting two bytes of a new command. The mmc-spi driver will not detect the R1 response from the SD card, since it is sent too early, and offset by two bits. This patch fixes transfer errors when using SD cards with dw spi. Signed-off-by: Sean Anderson Reviewed-by: Jagan Teki Reviewed-by: Jagan Teki --- diff --git a/drivers/spi/designware_spi.c b/drivers/spi/designware_spi.c index 2559aac2e9..74372171aa 100644 --- a/drivers/spi/designware_spi.c +++ b/drivers/spi/designware_spi.c @@ -322,7 +322,7 @@ static inline u32 rx_max(struct dw_spi_priv *priv) static void dw_writer(struct dw_spi_priv *priv) { u32 max = tx_max(priv); - u16 txw = 0; + u16 txw = 0xFFFF; while (max--) { /* Set the tx word if the transfer's original "tx" is not null */