[PATCH AUTOSEL 5.2 007/249] spi: rockchip: turn down tx dma bursts

[PATCH AUTOSEL 5.2 007/249] spi: rockchip: turn down tx dma bursts

[Sasha Levin]

From: Emil Renner Berthing <kernel@esmil.dk>

[ Upstream commit 47300728fb213486a830565d2af49da967c9d16a ]

This fixes tx and bi-directional dma transfers on rk3399-gru-kevin.

It seems the SPI fifo must have room for 2 bursts when the dma_tx_req
signal is generated or it might skip some words. This in turn makes
the rx dma channel never complete for bi-directional transfers.

Fix it by setting tx burst length to fifo_len / 4 and the dma
watermark to fifo_len / 2.

However the rk3399 TRM says (sic):
"DMAC support incrementing-address burst and fixed-address burst. But in
the case of access SPI and UART at byte or halfword size, DMAC only
support fixed-address burst and the address must be aligned to word."

So this relies on fifo_len being a multiple of 16 such that the
burst length (= fifo_len / 4) is a multiple of 4 and the addresses
will be word-aligned.

Fixes: dcfc861d24ec ("spi: rockchip: adjust dma watermark and burstlen")
Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/spi/spi-rockchip.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index 9b91188a85f9..2cc6d9951b52 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -417,7 +417,7 @@ static int rockchip_spi_prepare_dma(struct rockchip_spi *rs,
 			.direction = DMA_MEM_TO_DEV,
 			.dst_addr = rs->dma_addr_tx,
 			.dst_addr_width = rs->n_bytes,
-			.dst_maxburst = rs->fifo_len / 2,
+			.dst_maxburst = rs->fifo_len / 4,
 		};
 
 		dmaengine_slave_config(master->dma_tx, &txconf);
@@ -518,7 +518,7 @@ static void rockchip_spi_config(struct rockchip_spi *rs,
 	else
 		writel_relaxed(rs->fifo_len / 2 - 1, rs->regs + ROCKCHIP_SPI_RXFTLR);
 
-	writel_relaxed(rs->fifo_len / 2 - 1, rs->regs + ROCKCHIP_SPI_DMATDLR);
+	writel_relaxed(rs->fifo_len / 2, rs->regs + ROCKCHIP_SPI_DMATDLR);
 	writel_relaxed(0, rs->regs + ROCKCHIP_SPI_DMARDLR);
 	writel_relaxed(dmacr, rs->regs + ROCKCHIP_SPI_DMACR);
 
-- 
2.20.1

[PATCH AUTOSEL 5.2 131/249] spi: fix ctrl->num_chipselect constraint

[Sasha Levin]

From: Tudor Ambarus <tudor.ambarus@microchip.com>

[ Upstream commit f9481b08220d7dc1ff21e296a330ee8b721b44e4 ]

at91sam9g25ek showed the following error at probe:
atmel_spi f0000000.spi: Using dma0chan2 (tx) and dma0chan3 (rx)
for DMA transfers
atmel_spi: probe of f0000000.spi failed with error -22

Commit 0a919ae49223 ("spi: Don't call spi_get_gpio_descs() before device name is set")
moved the calling of spi_get_gpio_descs() after ctrl->dev is set,
but didn't move the !ctrl->num_chipselect check. When there are
chip selects in the device tree, the spi-atmel driver lets the
SPI core discover them when registering the SPI master.
The ctrl->num_chipselect is thus expected to be set by
spi_get_gpio_descs().

Move the !ctlr->num_chipselect after spi_get_gpio_descs() as it was
before the aforementioned commit. While touching this block, get rid
of the explicit comparison with 0 and update the commenting style.

Fixes: 0a919ae49223 ("spi: Don't call spi_get_gpio_descs() before device name is set")
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/spi/spi.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 5e4654032bfa..29916e446143 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2286,11 +2286,6 @@ int spi_register_controller(struct spi_controller *ctlr)
 	if (status)
 		return status;
 
-	/* even if it's just one always-selected device, there must
-	 * be at least one chipselect
-	 */
-	if (ctlr->num_chipselect == 0)
-		return -EINVAL;
 	if (ctlr->bus_num >= 0) {
 		/* devices with a fixed bus num must check-in with the num */
 		mutex_lock(&board_lock);
@@ -2361,6 +2356,13 @@ int spi_register_controller(struct spi_controller *ctlr)
 		}
 	}
 
+	/*
+	 * Even if it's just one always-selected device, there must
+	 * be at least one chipselect.
+	 */
+	if (!ctlr->num_chipselect)
+		return -EINVAL;
+
 	status = device_add(&ctlr->dev);
 	if (status < 0) {
 		/* free bus id */
-- 
2.20.1