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SubjectRe: [PATCH 2/2] CHROMIUM: tpm: tpm_i2c_infineon: Lock the I2C adapter for a sequence of requests.

Signed-off-by: Marcel Selhorst <tpmdd@selhorst.net>

Zitat von Peter Huewe <peter.huewe@infineon.com>:

> From: Bryan Freed <bfreed@chromium.org>
>
> This is derived from Peter Huewe's recommended fix:
>
> On some ChromeOS systems, a TPM sharing the I2C bus with another device
> gets confused when it sees I2C requests to that other device.
> This change locks the I2C adapter for the duration of the full sequence
> of I2C requests the TPM needs to complete.
>
> smbus_xfer is not supported, but SMBUS is not supported by the original
> driver, either.
>
> Signed-off-by: Bryan Freed <bfreed@chromium.org>
> Signed-off-by: Peter Huewe <peter.huewe@infineon.com>
> ---
> drivers/char/tpm/tpm_i2c_infineon.c | 45
> +++++++++++++++++++++++++++++++---
> 1 files changed, 41 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_i2c_infineon.c
> b/drivers/char/tpm/tpm_i2c_infineon.c
> index 54b9a5e..1794a09 100644
> --- a/drivers/char/tpm/tpm_i2c_infineon.c
> +++ b/drivers/char/tpm/tpm_i2c_infineon.c
> @@ -68,6 +68,31 @@ struct tpm_inf_dev {
> static struct tpm_inf_dev tpm_dev;
> static struct i2c_driver tpm_tis_i2c_driver;
>
> +
> +/*
> + * Copy i2c-core:i2c_transfer() as close as possible without the
> adapter locks
> + * and algorithm check. These are done by the caller for atomicity.
> + * Unfortunately we have to use this as a workaround in multislave
> environments
> + * as no other suitable and working mechanism is available.
> + */
> +static int i2c_transfer_nolock(struct i2c_adapter *adap, struct
> i2c_msg *msgs,
> + int num)
> +{
> + unsigned long orig_jiffies;
> + int ret, try;
> +
> + /* Retry automatically on arbitration loss */
> + orig_jiffies = jiffies;
> + for (ret = 0, try = 0; try <= adap->retries; try++) {
> + ret = adap->algo->master_xfer(adap, msgs, num);
> + if (ret != -EAGAIN)
> + break;
> + if (time_after(jiffies, orig_jiffies + adap->timeout))
> + break;
> + }
> + return ret;
> +}
> +
> /*
> * iic_tpm_read() - read from TPM register
> * @addr: register address to read from
> @@ -96,8 +121,13 @@ static int iic_tpm_read(u8 addr, u8 *buffer, size_t len)
> int rc;
> int count;
>
> + /* Lock the adapter for the duration of the whole sequence. */
> + if (!tpm_dev.client->adapter->algo->master_xfer)
> + return -EOPNOTSUPP;
> + i2c_lock_adapter(tpm_dev.client->adapter);
> +
> for (count = 0; count < MAX_COUNT; count++) {
> - rc = i2c_transfer(tpm_dev.client->adapter, &msg1, 1);
> + rc = i2c_transfer_nolock(tpm_dev.client->adapter, &msg1, 1);
> if (rc > 0)
> break; /* break here to skip sleep */
>
> @@ -105,19 +135,21 @@ static int iic_tpm_read(u8 addr, u8 *buffer,
> size_t len)
> }
>
> if (rc <= 0)
> - return -EIO;
> + goto out;
>
> /* After the TPM has successfully received the register address it needs
> * some time, thus we're sleeping here again, before retrieving the data
> */
> for (count = 0; count < MAX_COUNT; count++) {
> usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);
> - rc = i2c_transfer(tpm_dev.client->adapter, &msg2, 1);
> + rc = i2c_transfer_nolock(tpm_dev.client->adapter, &msg2, 1);
> if (rc > 0)
> break;
>
> }
>
> +out:
> + i2c_unlock_adapter(tpm_dev.client->adapter);
> if (rc <= 0)
> return -EIO;
>
> @@ -136,6 +168,10 @@ static int iic_tpm_write_generic(u8 addr, u8
> *buffer, size_t len,
> if (len > TPM_BUFSIZE)
> return -EINVAL;
>
> + if (!tpm_dev.client->adapter->algo->master_xfer)
> + return -EOPNOTSUPP;
> + i2c_lock_adapter(tpm_dev.client->adapter);
> +
> /* prepend the 'register address' to the buffer */
> tpm_dev.buf[0] = addr;
> memcpy(&(tpm_dev.buf[1]), buffer, len);
> @@ -145,13 +181,14 @@ static int iic_tpm_write_generic(u8 addr, u8
> *buffer, size_t len,
> * cannot rely on the standard behavior of i2c_transfer.
> */
> for (count = 0; count < max_count; count++) {
> - rc = i2c_transfer(tpm_dev.client->adapter, &msg1, 1);
> + rc = i2c_transfer_nolock(tpm_dev.client->adapter, &msg1, 1);
> if (rc > 0)
> break;
>
> usleep_range(sleep_low, sleep_hi);
> }
>
> + i2c_unlock_adapter(tpm_dev.client->adapter);
> if (rc <= 0)
> return -EIO;
>
> --
> 1.7.6.msysgit.0





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