On Thu, Sep 17, 2026 at 02:42:11PM +0200, Stefano Radaelli wrote: > From: Stefano Radaelli <[email protected]> > > The common TPM Device Tree binding already documents resets and > reset-gpios, but the TIS I2C driver never requests a reset control. > As a result, an I2C TPM held in reset by board wiring remains > inaccessible and the first register access during probe fails. > > Request the optional reset control and deassert it before > communicating with the TPM. This keeps existing boards without a reset > line unchanged while allowing platforms using resets or reset-gpios to > release the TPM before probe continues. > > Tested on a Variscite DART-MX95 with an ST33KTPM2XI2C TPM using > reset-gpios. > > Signed-off-by: Stefano Radaelli <[email protected]> > --- > drivers/char/tpm/tpm_tis_i2c.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/char/tpm/tpm_tis_i2c.c b/drivers/char/tpm/tpm_tis_i2c.c > index d55f30fef00a..cde0b093ed58 100644 > --- a/drivers/char/tpm/tpm_tis_i2c.c > +++ b/drivers/char/tpm/tpm_tis_i2c.c > @@ -12,6 +12,7 @@ > > #include <linux/i2c.h> > #include <linux/crc-ccitt.h> > +#include <linux/reset.h> > #include "tpm_tis_core.h" > > /* TPM registers */ > @@ -330,6 +331,7 @@ static const struct tpm_tis_phy_ops tpm_i2c_phy_ops = { > static int tpm_tis_i2c_probe(struct i2c_client *dev) > { > struct tpm_tis_i2c_phy *phy; > + struct reset_control *reset; > const u8 crc_enable = 1; > const u8 locality = 0; > int ret; > @@ -346,6 +348,16 @@ static int tpm_tis_i2c_probe(struct i2c_client *dev) > set_bit(TPM_TIS_DEFAULT_CANCELLATION, &phy->priv.flags); > phy->i2c_client = dev; > > + reset = devm_reset_control_get_optional_exclusive(&dev->dev, NULL); > + if (IS_ERR(reset)) > + return dev_err_probe(&dev->dev, PTR_ERR(reset), > + "failed to get reset control\n"); > + > + ret = reset_control_deassert(reset); > + if (ret) > + return dev_err_probe(&dev->dev, ret, > + "failed to deassert reset\n"); > + > /* must precede all communication with the tpm */ > ret = tpm_tis_i2c_init_guard_time(phy); > if (ret) > -- > 2.47.3 >
Reviewed-by: Jarkko Sakkinen <[email protected]> BR, Jarkko
