On Sun, Mar 22, 2020 at 04:39:58AM +0300, Dmitry Osipenko wrote: > 22.03.2020 00:03, Michał Mirosław пишет: > > Implement basic support for atomic write - enough to get a simple > > write to PMIC on shutdown. Only for chips having ALT_CMD register, > > eg. SAMA5D2. > > > > Signed-off-by: Michał Mirosław <mirq-linux@xxxxxxxxxxxx> > > --- > > v2: remove runtime-PM usage > > switch to readl*poll*atomic() for transfer completion wait > > --- > > drivers/i2c/busses/i2c-at91-master.c | 69 +++++++++++++++++++++++++++- > > 1 file changed, 67 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c > > index ba6fbb9c7390..d9226207157a 100644 > > --- a/drivers/i2c/busses/i2c-at91-master.c > > +++ b/drivers/i2c/busses/i2c-at91-master.c > > @@ -21,6 +21,7 @@ > > #include <linux/i2c.h> > > #include <linux/interrupt.h> > > #include <linux/io.h> > > +#include <linux/iopoll.h> > > #include <linux/of.h> > > #include <linux/of_device.h> > > #include <linux/platform_device.h> > > @@ -709,6 +710,69 @@ static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num) > > return ret; > > } > > > > +static int at91_twi_xfer_atomic(struct i2c_adapter *adap, struct i2c_msg *msg, int num) > > +{ > > + struct at91_twi_dev *dev = i2c_get_adapdata(adap); > > + unsigned long timeout; > > + struct pinctrl *pins; > > + __u32 stat; > > + int ret; > > + > > + /* FIXME: only single write request supported to 7-bit addr */ > > + if (num != 1) > > + return -EOPNOTSUPP; > > + if (msg->flags & I2C_M_RD) > > + return -EOPNOTSUPP; > > + if (msg->flags & I2C_M_TEN) > > + return -EOPNOTSUPP; > > + if (msg->len > dev->fifo_size && msg->len > 1) > > + return -EOPNOTSUPP; > > + if (!dev->pdata->has_alt_cmd) > > + return -EOPNOTSUPP; > > + > > + pins = pinctrl_get_select_default(&adap->dev); > > + > > + ret = clk_prepare_enable(twi_dev->clk); > > Hello Michał, > > Please see comments to the clk_prepare_enable() and clk_prepare(). > > /* clk_prepare_enable helps cases using clk_enable in non-atomic context. */ > static inline int clk_prepare_enable(struct clk *clk) > ... > * clk_prepare may sleep, which differentiates it from clk_enable. > Yes, it may. Though in this case unlikely. Even though clk_prepare() takes a mutex, this is running only after there are no more processes in the system, so there are no possible contenders. Best Regards, Michał Mirosław