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SMBus slave configuration is activated by CFG_SEL[1:0]=0x1 pins state. This is the mode the hub is supposed to be to let this driver work correctly. But a race condition might happen right after reset is cleared due to CFG_SEL[0] pin being multiplexed with SMBus SCL function. In case if the reset pin is handled by a i2c GPIO expander, which is also placed at the same i2c-bus segment as the usb251x SMB-interface connected to, then the hub reset clearance might cause the CFG_SEL[0] being latched in unpredictable state. So sometimes the hub configuration mode might be 0x1 (as expected), but sometimes being 0x0, which doesn't imply to have the hub SMBus-slave interface activated and consequently causes this driver failure. In order to fix the problem we must make sure the GPIO-reset chip doesn't reside the same i2c-bus segment as the SMBus-interface of the hub. If it doesn't, we can safely block the segment for the time the reset is cleared to prevent anyone generating a traffic at the i2c-bus SCL lane connected to the CFG_SEL[0] pin. But if it does, nothing we can do, so just return an error. If we locked the i2c-bus segment and tried to communicate with the GPIO-expander, it would cause a deadlock. If we didn't lock the i2c-bus segment, it would randomly cause the CFG_SEL[0] bit flip. Signed-off-by: Serge Semin <fancer.lancer@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| c67x00 | ||
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| common | ||
| core | ||
| dwc2 | ||
| dwc3 | ||
| early | ||
| gadget | ||
| host | ||
| image | ||
| isp1760 | ||
| misc | ||
| mon | ||
| mtu3 | ||
| musb | ||
| phy | ||
| renesas_usbhs | ||
| roles | ||
| serial | ||
| storage | ||
| typec | ||
| usbip | ||
| wusbcore | ||
| Kconfig | ||
| Makefile | ||
| usb-skeleton.c | ||