| Message ID | 9f37f64e-f5b8-4928-8716-6d2846c2688a@gmail.com |
|---|---|
| Headers | show |
| Series | i2c: Support i2c_register_spd() on multiplexed bus segments | expand |
On 13.01.2024 12:23, Heiner Kallweit wrote: > i801 is the last bus driver supporting I2C_CLASS_SPD. It's used for > device probing on muxed bus segments. Only known use case so far is > systems with more than 8 memory modules (with thermal sensor) on > muxed smbus segments. > As discussed with Jean, to be able to remove I2C_CLASS_SPD completely > the following has to be done: > > 1. Extend i2c_register_spd() for use on muxed bus segments > 2. Enable explicit instantiation of thermal sensors on memory modules > 3. Extend i801 to call i2c_register_spd() on muxed bus segments > > Step 2 has been accomplished: > caba40ec3531 ("eeprom: at24: Probe for DDR3 thermal sensor in the SPD case") > 393bd1000f81 ("eeprom: ee1004: add support for temperature sensor") > > Patch 1 does step 1 > Patches 2 and 3 provide the basis for patch 4 > Patch 4 does step 3 > > Note: i801 creates the mux platform device, loading and probing of the > mux driver may be asynchronous. Therefore we can't call i2c_register_spd() > for the muxed segments from i801. Instead we have to add a flag to the > platform data, so that the mux driver knows it's supposed to call > i2c_register_spd(). > > This series replaces the earlier RFC series. > > v2: > - remove now obsolete comment in patch 1 > - fix link error in some configs in patch 2 > > Heiner Kallweit (4): > i2c: smbus: Prepare i2c_register_spd for usage on muxed segments > i2c: mux: add basic support for calling i2c_register_spd on muxed bus > segments > i2c: mux: gpio: Allow to call i2c_register_spd on a muxed segment > i2c: i801: Call i2c_register_spd() on muxed bus segments > > drivers/i2c/Kconfig | 1 + > drivers/i2c/busses/i2c-i801.c | 1 + > drivers/i2c/i2c-mux.c | 4 ++++ > drivers/i2c/i2c-smbus.c | 20 ++++++++++++-------- > drivers/i2c/muxes/i2c-mux-gpio.c | 1 + > include/linux/i2c-mux.h | 1 + > include/linux/platform_data/i2c-mux-gpio.h | 2 ++ > 7 files changed, 22 insertions(+), 8 deletions(-) > Any further feedback on this series, or is it ready to go?
Hi Heiner, > Note: i801 creates the mux platform device, loading and probing of the > mux driver may be asynchronous. Therefore we can't call i2c_register_spd() > for the muxed segments from i801. Instead we have to add a flag to the > platform data, so that the mux driver knows it's supposed to call > i2c_register_spd(). Has it been considered to use a bus_notifier and check for BUS_NOTIFY_BOUND_DRIVER? I'd really like to keep it inside i801 if possible. First, all these flags in mux drivers only for this corner case are relatively intrusive. Second, selecting SMBUS for I2C_MUX is also a tad too much for my taste. I understand that removing CLASS_SPD is a worthy goal. So, if all fails we could still try this. But I'd think with bus_notifiers it should be possible to keep it all in i801. Do you think this could work? Happy hacking, Wolfram
On 21.02.2024 18:19, Wolfram Sang wrote: > Hi Heiner, > >> Note: i801 creates the mux platform device, loading and probing of the >> mux driver may be asynchronous. Therefore we can't call i2c_register_spd() >> for the muxed segments from i801. Instead we have to add a flag to the >> platform data, so that the mux driver knows it's supposed to call >> i2c_register_spd(). > > Has it been considered to use a bus_notifier and check for > BUS_NOTIFY_BOUND_DRIVER? > > I'd really like to keep it inside i801 if possible. First, all these > flags in mux drivers only for this corner case are relatively intrusive. > Second, selecting SMBUS for I2C_MUX is also a tad too much for my taste. > Right, it's not as clean as I would like to have it. So far I didn't see any other/better option. > I understand that removing CLASS_SPD is a worthy goal. So, if all fails > we could still try this. But I'd think with bus_notifiers it should be > possible to keep it all in i801. > > Do you think this could work? > Thanks for the hint. I have to admit I wasn't aware of this option. I'll check and will come back to you. > Happy hacking, > > Wolfram > Heiner
On 21.02.2024 18:19, Wolfram Sang wrote: > Hi Heiner, > >> Note: i801 creates the mux platform device, loading and probing of the >> mux driver may be asynchronous. Therefore we can't call i2c_register_spd() >> for the muxed segments from i801. Instead we have to add a flag to the >> platform data, so that the mux driver knows it's supposed to call >> i2c_register_spd(). > > Has it been considered to use a bus_notifier and check for > BUS_NOTIFY_BOUND_DRIVER? > I checked, and it looks like this: Best would be to check for binding gpio mux driver to platform device "i2c-mux-gpio" has completed. But the bus notification doesn't work for platform devices. Instead we can check for the BUS_NOTIFY_ADD_DEVICE event for the child i2c adapters. This *should* work. I tested that the events are properly recognized. However I don't have hw with a muxed SMBUS, so I can't test the actual functionality. I'll submit a RFC patch. > I'd really like to keep it inside i801 if possible. First, all these > flags in mux drivers only for this corner case are relatively intrusive. > Second, selecting SMBUS for I2C_MUX is also a tad too much for my taste. > > I understand that removing CLASS_SPD is a worthy goal. So, if all fails > we could still try this. But I'd think with bus_notifiers it should be > possible to keep it all in i801. > > Do you think this could work? > > Happy hacking, > > Wolfram > Heiner
i801 is the last bus driver supporting I2C_CLASS_SPD. It's used for device probing on muxed bus segments. Only known use case so far is systems with more than 8 memory modules (with thermal sensor) on muxed smbus segments. As discussed with Jean, to be able to remove I2C_CLASS_SPD completely the following has to be done: 1. Extend i2c_register_spd() for use on muxed bus segments 2. Enable explicit instantiation of thermal sensors on memory modules 3. Extend i801 to call i2c_register_spd() on muxed bus segments Step 2 has been accomplished: caba40ec3531 ("eeprom: at24: Probe for DDR3 thermal sensor in the SPD case") 393bd1000f81 ("eeprom: ee1004: add support for temperature sensor") Patch 1 does step 1 Patches 2 and 3 provide the basis for patch 4 Patch 4 does step 3 Note: i801 creates the mux platform device, loading and probing of the mux driver may be asynchronous. Therefore we can't call i2c_register_spd() for the muxed segments from i801. Instead we have to add a flag to the platform data, so that the mux driver knows it's supposed to call i2c_register_spd(). This series replaces the earlier RFC series. v2: - remove now obsolete comment in patch 1 - fix link error in some configs in patch 2 Heiner Kallweit (4): i2c: smbus: Prepare i2c_register_spd for usage on muxed segments i2c: mux: add basic support for calling i2c_register_spd on muxed bus segments i2c: mux: gpio: Allow to call i2c_register_spd on a muxed segment i2c: i801: Call i2c_register_spd() on muxed bus segments drivers/i2c/Kconfig | 1 + drivers/i2c/busses/i2c-i801.c | 1 + drivers/i2c/i2c-mux.c | 4 ++++ drivers/i2c/i2c-smbus.c | 20 ++++++++++++-------- drivers/i2c/muxes/i2c-mux-gpio.c | 1 + include/linux/i2c-mux.h | 1 + include/linux/platform_data/i2c-mux-gpio.h | 2 ++ 7 files changed, 22 insertions(+), 8 deletions(-)