From: Tobias Schramm <t.schramm@manjaro.org>
Date: Fri, 27 Aug 2021 05:03:57 +0000 (+0200)
Subject: spi: rockchip: handle zero length transfers without timing out
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=5457773ef99f25fcc4b238ac76b68e28273250f4;p=linux.git

spi: rockchip: handle zero length transfers without timing out

Previously zero length transfers submitted to the Rokchip SPI driver would
time out in the SPI layer. This happens because the SPI peripheral does
not trigger a transfer completion interrupt for zero length transfers.

Fix that by completing zero length transfers immediately at start of
transfer.

Signed-off-by: Tobias Schramm <t.schramm@manjaro.org>
Link: https://lore.kernel.org/r/20210827050357.165409-1-t.schramm@manjaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>
---

diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index 540861ca2ba37..553b6b9d02222 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -600,6 +600,12 @@ static int rockchip_spi_transfer_one(
 	int ret;
 	bool use_dma;
 
+	/* Zero length transfers won't trigger an interrupt on completion */
+	if (!xfer->len) {
+		spi_finalize_current_transfer(ctlr);
+		return 1;
+	}
+
 	WARN_ON(readl_relaxed(rs->regs + ROCKCHIP_SPI_SSIENR) &&
 		(readl_relaxed(rs->regs + ROCKCHIP_SPI_SR) & SR_BUSY));