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Subject[PATCH v4] tpm_tis_spi: Use DMA-safe memory for SPI transfers
Date
The buffers used as tx_buf/rx_buf in a SPI transfer need to be DMA-safe.
This cannot be guaranteed for the buffers passed to tpm_tis_spi_read_bytes
and tpm_tis_spi_write_bytes. Therefore, we need to use our own DMA-safe
buffer and copy the data to/from it.

The buffer needs to be allocated separately, to ensure that it is
cacheline-aligned and not shared with other data, so that DMA can work
correctly.

Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy")
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
---
v2:
- Updated commit message with more explanations.
v3:
- Split into two patches, one for making the buffers DMA-safe and another
for using only a single buffer.
v4:
- Back to one patch, to fix conflicts with new const buffers.

drivers/char/tpm/tpm_tis_spi.c | 45 +++++++++++++++++++++++++-----------------
1 file changed, 27 insertions(+), 18 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
index e49f5b9..8ab0bd8 100644
--- a/drivers/char/tpm/tpm_tis_spi.c
+++ b/drivers/char/tpm/tpm_tis_spi.c
@@ -46,9 +46,7 @@
struct tpm_tis_spi_phy {
struct tpm_tis_data priv;
struct spi_device *spi_device;
-
- u8 tx_buf[4];
- u8 rx_buf[4];
+ u8 *iobuf;
};

static inline struct tpm_tis_spi_phy *to_tpm_tis_spi_phy(struct tpm_tis_data *data)
@@ -71,14 +69,14 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
while (len) {
transfer_len = min_t(u16, len, MAX_SPI_FRAMESIZE);

- phy->tx_buf[0] = (in ? 0x80 : 0) | (transfer_len - 1);
- phy->tx_buf[1] = 0xd4;
- phy->tx_buf[2] = addr >> 8;
- phy->tx_buf[3] = addr;
+ phy->iobuf[0] = (in ? 0x80 : 0) | (transfer_len - 1);
+ phy->iobuf[1] = 0xd4;
+ phy->iobuf[2] = addr >> 8;
+ phy->iobuf[3] = addr;

memset(&spi_xfer, 0, sizeof(spi_xfer));
- spi_xfer.tx_buf = phy->tx_buf;
- spi_xfer.rx_buf = phy->rx_buf;
+ spi_xfer.tx_buf = phy->iobuf;
+ spi_xfer.rx_buf = phy->iobuf;
spi_xfer.len = 4;
spi_xfer.cs_change = 1;

@@ -88,9 +86,9 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
if (ret < 0)
goto exit;

- if ((phy->rx_buf[3] & 0x01) == 0) {
+ if ((phy->iobuf[3] & 0x01) == 0) {
// handle SPI wait states
- phy->tx_buf[0] = 0;
+ phy->iobuf[0] = 0;

for (i = 0; i < TPM_RETRY; i++) {
spi_xfer.len = 1;
@@ -99,7 +97,7 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
ret = spi_sync_locked(phy->spi_device, &m);
if (ret < 0)
goto exit;
- if (phy->rx_buf[0] & 0x01)
+ if (phy->iobuf[0] & 0x01)
break;
}

@@ -112,8 +110,14 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
spi_xfer.cs_change = 0;
spi_xfer.len = transfer_len;
spi_xfer.delay_usecs = 5;
- spi_xfer.tx_buf = out;
- spi_xfer.rx_buf = in;
+
+ if (in) {
+ spi_xfer.tx_buf = NULL;
+ } else if (out) {
+ spi_xfer.rx_buf = NULL;
+ memcpy(phy->iobuf, out, transfer_len);
+ out += transfer_len;
+ }

spi_message_init(&m);
spi_message_add_tail(&spi_xfer, &m);
@@ -121,11 +125,12 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
if (ret < 0)
goto exit;

- len -= transfer_len;
- if (in)
+ if (in) {
+ memcpy(in, phy->iobuf, transfer_len);
in += transfer_len;
- if (out)
- out += transfer_len;
+ }
+
+ len -= transfer_len;
}

exit:
@@ -191,6 +196,10 @@ static int tpm_tis_spi_probe(struct spi_device *dev)

phy->spi_device = dev;

+ phy->iobuf = devm_kmalloc(&dev->dev, MAX_SPI_FRAMESIZE, GFP_KERNEL);
+ if (!phy->iobuf)
+ return -ENOMEM;
+
return tpm_tis_core_init(&dev->dev, &phy->priv, -1, &tpm_spi_phy_ops,
NULL);
}
--
2.7.4
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