> -----Original Message----- > From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> > Sent: Tuesday, September 3, 2024 12:10 PM > To: Pandey, Radhey Shyam <radhey.shyam.pandey@xxxxxxx> > Cc: mka@xxxxxxxxxxxx; sakari.ailus@xxxxxxxxxxxxxxx; > wentong.wu@xxxxxxxxx; javier.carrasco@xxxxxxxxxxxxxx; > stefan.eichenberger@xxxxxxxxxxx; francesco.dolcini@xxxxxxxxxxx; > jbrunet@xxxxxxxxxxxx; macpaul.lin@xxxxxxxxxxxx; > frieder.schrempf@xxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; git (AMD-Xilinx) <git@xxxxxxx> > Subject: Re: [PATCH v4 2/2] usb: misc: onboard_usb_dev: add Microchip > usb5744 SMBus programming support > > On Sun, Sep 01, 2024 at 05:38:39PM +0530, Radhey Shyam Pandey wrote: > > usb5744 supports SMBus Configuration and it may be configured via the > > SMBus slave interface during the hub start-up configuration stage. > > > > To program it driver uses i2c-bus phandle (added in commit '02be19e914b8 > > dt-bindings: usb: Add support for Microchip usb5744 hub controller') to > > get i2c client device and then based on usb5744 compatible check calls > > usb5744 i2c default initialization sequence. > > > > Apart from the USB command attach, prevent the hub from suspend. > > when the USB Attach with SMBus (0xAA56) command is issued to the hub, > > the hub is getting enumerated and then it puts in a suspend mode. > > This causes the hub to NAK any SMBus access made by the SMBus Master > > during this period and not able to see the hub's slave address while > > running the "i2c probe" command. > > > > Prevent the MCU from putting the HUB in suspend mode through register > > write. The BYPASS_UDC_SUSPEND bit (Bit 3) of the RuntimeFlags2 > > register at address 0x411D controls this aspect of the hub. The > > BYPASS_UDC_SUSPEND bit in register 0x411Dh must be set to ensure that > the > > MCU is always enabled and ready to respond to SMBus runtime > commands. > > This register needs to be written before the USB attach command is issued. > > > > The byte sequence is as follows: > > Slave addr: 0x2d 00 00 05 00 01 41 1D 08 > > Slave addr: 0x2d 99 37 00 > > Slave addr: 0x2d AA 56 00 > > > > Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxx> > > --- > > Changes for v4: > > - Fix error: implicit declaration of function 'i2c_smbus_*' APIs by > > introducing a dependency on I2C_CONFIG. This error is reported > > by kernel test on v3 series and usb:usb-testing 20/25 branch. > > https://lore.kernel.org/all/2024082503-uncoated-chaperone- > 7f70@gregkh > > > > Changes for v3: > > - Add comment for UDC suspend sequence. > > - Drop USB5744_CREG_MEM_NBYTES and USB5744_CREG_NBYTES and > replace > > it with literal + comment. > > - Move microchip defines to source file. > > > > Changes for v2: > > - Move power on reset delay to separate patch. > > - Switch to compatible based check for calling usb5755 > > onboard_dev_5744_i2c_init(). This is done to make > > onboard_dev_5744_i2c_init() as static. > > - Fix subsystem "usb: misc: onboard_usb_dev:..." > > - Use #define for different register bits instead of magic values. > > - Use err_power_off label name. > > - Modified commit description to be in sync with v2 changes. > > --- > > drivers/usb/misc/Kconfig | 2 +- > > drivers/usb/misc/onboard_usb_dev.c | 73 > ++++++++++++++++++++++++++++++ > > 2 files changed, 74 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig > > index 50b86d531701..cb5e47d439ab 100644 > > --- a/drivers/usb/misc/Kconfig > > +++ b/drivers/usb/misc/Kconfig > > @@ -318,7 +318,7 @@ config BRCM_USB_PINMAP > > > > config USB_ONBOARD_DEV > > tristate "Onboard USB device support" > > - depends on OF > > + depends on OF && I2C > > This feels wrong. > > While a single device that this driver supports might need i2c, not all > of the devices do, so you have the potential to drag in a bunch of code > here for devices that do not have/need i2c at all, right? > > Any way to "split this out" into a smaller chunk? Or better yet, just > detect at runtime if you need/want to call those i2c functions (and they > should have no-ops for when i2c is not enabled, right?) In onboard driver I am calling onboard_dev_5744_i2c_init() by detecting at runtime if "i2c-bus" phandle is present. But the problem is i2c_smbus_* APIs are declared and defined only for #if IS_ENABLED(CONFIG_I2C). Do you think we should implement no-ops for I2C smbus APIs (in linux/i2c.h)? OR a simpler alternative would be to add #if IS_ENABLED(CONFIG_I2C) check in the onboard_*_i2c_init() and return error code if CONFIG_I2C is not defined ? Did a grep on #if IS_ENABLED(CONFIG_I2C) and find couple of drivers using this approach. Thanks, Radhey
