linux-kernel - [PATCH AUTOSEL 5.10 01/23] spi: rockchip: handle zero length transfers without timing out

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Message-Id: <20210928055645.172544-1-sashal@kernel.org>
Date:   Tue, 28 Sep 2021 01:56:22 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Tobias Schramm <t.schramm@...jaro.org>,
        Mark Brown <broonie@...nel.org>,
        Sasha Levin <sashal@...nel.org>, heiko@...ech.de,
        linux-spi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.10 01/23] spi: rockchip: handle zero length transfers without timing out

From: Tobias Schramm <t.schramm@...jaro.org>

[ Upstream commit 5457773ef99f25fcc4b238ac76b68e28273250f4 ]

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@...jaro.org>
Link: https://lore.kernel.org/r/20210827050357.165409-1-t.schramm@manjaro.org
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/spi/spi-rockchip.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index 0aab37cd64e7..624273d0e727 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -582,6 +582,12 @@ 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));
 
-- 
2.33.0