On Wed, Sep 02, 2020 at 09:17:47AM +1200, Evan Nimmo wrote:
> If something goes wrong (such as the SCL being stuck low) then we need
> to reset the PCA chip. The issue with this is that on reset we lose all
> config settings and the chip ends up in a disabled state which results
> in a lock up/high cpu usage. We need to re-apply any configuration that
cpu -> CPU (I guess Wolfram can decide with this when applying)
> had previously been set and re-enable the chip.
FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Signed-off-by: Evan Nimmo <evan.nimmo@xxxxxxxxxxxxxxxxxxx>
> ---
> changes in v2:
> - changed lowercase "pca to uppercase "PCA".
> - reworded and reformatted the multiline comment.
> - moved the clock frequency KERN_INFO closer to the call that sets this.
> - moved the i2c_bus_settings struct to the more generic i2c.h and removed
> - the comments indicating this as being for the pca chip.
>
> drivers/i2c/algos/i2c-algo-pca.c | 36 +++++++++++++++++++++-----------
> include/linux/i2c-algo-pca.h | 1 +
> include/linux/i2c.h | 14 +++++++++++++
> 3 files changed, 39 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/i2c/algos/i2c-algo-pca.c b/drivers/i2c/algos/i2c-algo-pca.c
> index 710fbef9a9c2..8b98b737b499 100644
> --- a/drivers/i2c/algos/i2c-algo-pca.c
> +++ b/drivers/i2c/algos/i2c-algo-pca.c
> @@ -41,8 +41,22 @@ static void pca_reset(struct i2c_algo_pca_data *adap)
> pca_outw(adap, I2C_PCA_INDPTR, I2C_PCA_IPRESET);
> pca_outw(adap, I2C_PCA_IND, 0xA5);
> pca_outw(adap, I2C_PCA_IND, 0x5A);
> +
> + /*
> + * After a reset we need to re-apply any configuration
> + * (calculated in pca_init) to get the bus in a working state.
> + */
> + pca_outw(adap, I2C_PCA_INDPTR, I2C_PCA_IMODE);
> + pca_outw(adap, I2C_PCA_IND, adap->bus_settings.mode);
> + pca_outw(adap, I2C_PCA_INDPTR, I2C_PCA_ISCLL);
> + pca_outw(adap, I2C_PCA_IND, adap->bus_settings.tlow);
> + pca_outw(adap, I2C_PCA_INDPTR, I2C_PCA_ISCLH);
> + pca_outw(adap, I2C_PCA_IND, adap->bus_settings.thi);
> +
> + pca_set_con(adap, I2C_PCA_CON_ENSIO);
> } else {
> adap->reset_chip(adap->data);
> + pca_set_con(adap, I2C_PCA_CON_ENSIO | adap->bus_settings.clock_freq);
> }
> }
>
> @@ -423,13 +437,15 @@ static int pca_init(struct i2c_adapter *adap)
> " Use the nominal frequency.\n", adap->name);
> }
>
> - pca_reset(pca_data);
> -
> clock = pca_clock(pca_data);
> +
> printk(KERN_INFO "%s: Clock frequency is %dkHz\n",
> adap->name, freqs[clock]);
>
> - pca_set_con(pca_data, I2C_PCA_CON_ENSIO | clock);
> + /* Store settings as these will be needed when the PCA chip is reset */
> + pca_data->bus_settings.clock_freq = clock;
> +
> + pca_reset(pca_data);
> } else {
> int clock;
> int mode;
> @@ -496,19 +512,15 @@ static int pca_init(struct i2c_adapter *adap)
> thi = tlow * min_thi / min_tlow;
> }
>
> + /* Store settings as these will be needed when the PCA chip is reset */
> + pca_data->bus_settings.mode = mode;
> + pca_data->bus_settings.tlow = tlow;
> + pca_data->bus_settings.thi = thi;
> +
> pca_reset(pca_data);
>
> printk(KERN_INFO
> "%s: Clock frequency is %dHz\n", adap->name, clock * 100);
> -
> - pca_outw(pca_data, I2C_PCA_INDPTR, I2C_PCA_IMODE);
> - pca_outw(pca_data, I2C_PCA_IND, mode);
> - pca_outw(pca_data, I2C_PCA_INDPTR, I2C_PCA_ISCLL);
> - pca_outw(pca_data, I2C_PCA_IND, tlow);
> - pca_outw(pca_data, I2C_PCA_INDPTR, I2C_PCA_ISCLH);
> - pca_outw(pca_data, I2C_PCA_IND, thi);
> -
> - pca_set_con(pca_data, I2C_PCA_CON_ENSIO);
> }
> udelay(500); /* 500 us for oscillator to stabilise */
>
> diff --git a/include/linux/i2c-algo-pca.h b/include/linux/i2c-algo-pca.h
> index d03071732db4..97d1f4cd8e56 100644
> --- a/include/linux/i2c-algo-pca.h
> +++ b/include/linux/i2c-algo-pca.h
> @@ -64,6 +64,7 @@ struct i2c_algo_pca_data {
> * For PCA9665, use the frequency you want here. */
> unsigned int i2c_clock;
> unsigned int chip;
> + struct i2c_bus_settings bus_settings;
> };
>
> int i2c_pca_add_bus(struct i2c_adapter *);
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index fc55ea41d323..8c5138fbe532 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -724,6 +724,20 @@ struct i2c_adapter {
> };
> #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
>
> +/**
> + * struct i2c_bus_settings - The configured i2c bus settings
> + * @mode: Configured i2c bus mode
> + * @tlow: Configured SCL LOW period
> + * @thi: Configured SCL HIGH period
> + * @clock_freq: The configured clock frequency
> + */
> +struct i2c_bus_settings {
> + int mode;
> + int tlow;
> + int thi;
> + int clock_freq;
> +};
> +
> static inline void *i2c_get_adapdata(const struct i2c_adapter *adap)
> {
> return dev_get_drvdata(&adap->dev);
> --
> 2.27.0
>
--
With Best Regards,
Andy Shevchenko
