Hi Wojciech, Thank you for the patch. On Fri, Sep 13, 2024 at 06:51:16AM +0000, Wojciech Siudy (Nokia) wrote: > From: Wojciech Siudy <wojciech.siudy@xxxxxxxxx> > > If the channel selection or deselection times out, it indicates > a failure in the mux's I2C subsystem. Without sending a reset pulse, > a power-on-reset of the entire device would be required to restore > communication. > > The datasheet specifies a minimum hold time of 4 ns for the reset > pulse, but due to the path's capacitance and the mux having its own > clock, it is recommended to extend this to approximately 1 us. > > This option can be enabled using the i2c-mux-timeout-reset property > in the device tree and should only be used if the reset line is not > shared with other devices. > > Signed-off-by: Wojciech Siudy <wojciech.siudy@xxxxxxxxx> > --- > Changelog: > v2: > * Removed mail header from the commit log > * Decreased reset pulse hold time from 10 to 1 ms > v3: > * Make this functionality enabled by appropriate property in > devicetree > --- > drivers/i2c/muxes/i2c-mux-pca954x.c | 48 ++++++++++++++++++++++------- > 1 file changed, 37 insertions(+), 11 deletions(-) > > diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c > index 6f84018258c4..c9ac0f9c9408 100644 > --- a/drivers/i2c/muxes/i2c-mux-pca954x.c > +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c > @@ -110,6 +110,7 @@ struct pca954x { > u8 last_chan; /* last register value */ > /* MUX_IDLE_AS_IS, MUX_IDLE_DISCONNECT or >= 0 for channel */ > s32 idle_state; > + u8 timeout_reset; > > struct i2c_client *client; > > @@ -316,6 +317,30 @@ static u8 pca954x_regval(struct pca954x *data, u8 chan) > return 1 << chan; > } > > +static void pca954x_reset_deassert(struct pca954x *data) > +{ > + if (data->reset_cont) > + reset_control_deassert(data->reset_cont); > + else > + gpiod_set_value_cansleep(data->reset_gpio, 0); > +} > + > +static void pca954x_reset_assert(struct pca954x *data) > +{ > + if (data->reset_cont) > + reset_control_assert(data->reset_cont); > + else > + gpiod_set_value_cansleep(data->reset_gpio, 1); > +} > + > +static void pca954x_reset_mux(struct pca954x *data) > +{ > + dev_warn(&data->client->dev, "resetting the device\n"); > + pca954x_reset_assert(data); > + udelay(1); > + pca954x_reset_deassert(data); > +} > + > static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan) > { > struct pca954x *data = i2c_mux_priv(muxc); > @@ -329,6 +354,8 @@ static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan) > ret = pca954x_reg_write(muxc->parent, client, regval); > data->last_chan = ret < 0 ? 0 : regval; > } > + if (ret == -ETIMEDOUT && (data->reset_cont || data->reset_gpio)) > + pca954x_reset_mux(data); > > return ret; > } > @@ -338,6 +365,7 @@ static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan) > struct pca954x *data = i2c_mux_priv(muxc); > struct i2c_client *client = data->client; > s32 idle_state; > + int ret = 0; > > idle_state = READ_ONCE(data->idle_state); > if (idle_state >= 0) > @@ -347,13 +375,14 @@ static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan) > if (idle_state == MUX_IDLE_DISCONNECT) { > /* Deselect active channel */ > data->last_chan = 0; > - return pca954x_reg_write(muxc->parent, client, > - data->last_chan); > + ret = pca954x_reg_write(muxc->parent, client, data->last_chan); > + if (ret == -ETIMEDOUT && (data->reset_cont || data->reset_gpio)) > + pca954x_reset_mux(data); > } > > /* otherwise leave as-is */ > > - return 0; > + return ret; > } > > static ssize_t idle_state_show(struct device *dev, > @@ -543,14 +572,6 @@ static int pca954x_get_reset(struct device *dev, struct pca954x *data) > return 0; > } > > -static void pca954x_reset_deassert(struct pca954x *data) > -{ > - if (data->reset_cont) > - reset_control_deassert(data->reset_cont); > - else > - gpiod_set_value_cansleep(data->reset_gpio, 0); > -} > - > /* > * I2C init/probing/exit functions > */ > @@ -625,6 +646,11 @@ static int pca954x_probe(struct i2c_client *client) > data->idle_state = MUX_IDLE_DISCONNECT; > } > > + if (device_property_read_bool(dev, "i2c-mux-timeout-reset")) > + data->timeout_reset = 1; > + else > + data->timeout_reset = 0; timeout_reset is set but never used. Am I missing something ? > + > /* > * Write the mux register at addr to verify > * that the mux is in fact present. This also -- Regards, Laurent Pinchart