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Subject[PATCH] spi: rockchip: limit transfers to (64K - 1) bytes
Date
The Rockchip SPI controller's length register only supports 16-bits,
yielding a maximum length of 64KiB (the CTRLR1 register holds "length -
1"). Trying to transfer more than that (e.g., with a large SPI flash
read) will cause the driver to hang.

Now, it seems that while theoretically we should be able to program
CTRLR1 with 0xffff, and get a 64KiB transfer, but that also seems to
cause the core to choke, so stick with a maximum of 64K - 1 bytes --
i.e., 0xffff.

Signed-off-by: Brian Norris <briannorris@chromium.org>
---
drivers/spi/spi-rockchip.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)

diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index d840324bcc9f..0f89c2169c24 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -142,6 +142,12 @@
/* sclk_out: spi master internal logic in rk3x can support 50Mhz */
#define MAX_SCLK_OUT 50000000

+/*
+ * SPI_CTRLR1 is 16-bits, so we should support lengths of 0xffff + 1. However,
+ * the controller seems to hang when given 0x10000, so stick with this for now.
+ */
+#define ROCKCHIP_SPI_MAX_TRANLEN 0xffff
+
enum rockchip_ssi_type {
SSI_MOTO_SPI = 0,
SSI_TI_SSP,
@@ -573,6 +579,11 @@ static void rockchip_spi_config(struct rockchip_spi *rs)
dev_dbg(rs->dev, "cr0 0x%x, div %d\n", cr0, div);
}

+static size_t rockchip_spi_max_transfer_size(struct spi_device *spi)
+{
+ return ROCKCHIP_SPI_MAX_TRANLEN;
+}
+
static int rockchip_spi_transfer_one(
struct spi_master *master,
struct spi_device *spi,
@@ -589,6 +600,11 @@ static int rockchip_spi_transfer_one(
return -EINVAL;
}

+ if (xfer->len > ROCKCHIP_SPI_MAX_TRANLEN) {
+ dev_err(rs->dev, "Transfer is too long (%d)\n", xfer->len);
+ return -EINVAL;
+ }
+
rs->speed = xfer->speed_hz;
rs->bpw = xfer->bits_per_word;
rs->n_bytes = rs->bpw >> 3;
@@ -730,6 +746,7 @@ static int rockchip_spi_probe(struct platform_device *pdev)
master->prepare_message = rockchip_spi_prepare_message;
master->unprepare_message = rockchip_spi_unprepare_message;
master->transfer_one = rockchip_spi_transfer_one;
+ master->max_transfer_size = rockchip_spi_max_transfer_size;
master->handle_err = rockchip_spi_handle_err;

rs->dma_tx.ch = dma_request_chan(rs->dev, "tx");
--
2.8.0.rc3.226.g39d4020
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