On Tue, 7 May 2013 10:00:48 -0400 Jean-Francois Dagenais <jeff.dagen...@gmail.com> wrote:
> V2: use the new bus_mutex > > extract from http://datasheets.maximintegrated.com/en/ds/DS2408.pdf: > > Power-up timing > The DS2408 is sensitive to the power-on slew rate and can inadvertently > power up with a test mode feature enabled. When this occurs, the P0 port > does not respond to the Channel Access Write command. > For most reliable operation, it is recommended to disable the test mode > after every power-on reset using the Disable Test Mode sequence shown > below. The 64-bit ROM code must be transmitted in the same bit sequence > as with the Match ROM command, i.e., least significant bit first. This > precaution is recommended in parasite power mode (VCC pin connected to > GND) as well as with VCC power. > > Disable Test Mode: > RST,PD,96h,<64-bit DS2408 ROM Code>,3Ch,RST,PD > > ... > > --- a/drivers/w1/slaves/w1_ds2408.c > +++ b/drivers/w1/slaves/w1_ds2408.c > @@ -301,7 +301,32 @@ error: > return -EIO; > } > > +/** /** is used to introduce kerneldoc comments, but this isn't a kerneldoc comment. Just use /* here. > + * This is a special sequence we must do to ensure the P0 output is not stuck > + * in test mode. This is described in rev 2 of the ds2408's datasheet > + * (http://datasheets.maximintegrated.com/en/ds/DS2408.pdf) under > + * "APPLICATION INFORMATION/Power-up timing". > + */ > +static int w1_f29_disable_test_mode(struct w1_slave *sl) > +{ > + int res; > + u8 magic[10] = {0x96, }; > + u64 rn = le64_to_cpu(*((u64*)&sl->reg_num)); > + memcpy(&magic[1], &rn, 8); > + magic[9] = 0x3C; (please put a blank line between end-of-locals and start-of-code) The casting looks decidedly dodgy. I guess it won't cause an unalignned exception due to reg_num's alignment, but it appears to defeat the endianness handling in the definotion of `struct w1_reg_num'. Are you sure this will work OK with all architectures and both __LITTLE_ENDIAN_BITFIELD and __BIG_ENDIAN_BITFIELD? > + mutex_lock(&sl->master->bus_mutex); > > + res = w1_reset_bus(sl->master); > + if (res) > + goto out; > + w1_write_block(sl->master, magic, ARRAY_SIZE(magic)); > + > + res = w1_reset_bus(sl->master); > +out: > + mutex_unlock(&sl->master->bus_mutex); > + return res; > +} > > static struct bin_attribute w1_f29_sysfs_bin_files[] = { > { > @@ -362,6 +387,10 @@ static int w1_f29_add_slave(struct w1_slave *sl) > int err = 0; > int i; > > + err = w1_f29_disable_test_mode(sl); > + if (err) > + return err; > + > for (i = 0; i < ARRAY_SIZE(w1_f29_sysfs_bin_files) && !err; ++i) > err = sysfs_create_bin_file( > &sl->dev.kobj, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
