On 11/28/2017 2:35 PM, Greg Kroah-Hartman wrote: > On Tue, Nov 28, 2017 at 12:11:46PM -0500, Adam Wallis wrote: >> The xHCI driver currently has the IMOD set to 160, which >> translates to an IMOD interval of 40,000ns (160 * 250)ns >> [..] >> --- a/drivers/usb/host/xhci-plat.c >> +++ b/drivers/usb/host/xhci-plat.c >> @@ -23,6 +23,7 @@ >> #include "xhci-plat.h" >> #include "xhci-mvebu.h" >> #include "xhci-rcar.h" >> +#include "xhci-mtk.h" >> >> static struct hc_driver __read_mostly xhci_plat_hc_driver; >> >> @@ -269,6 +270,20 @@ static int xhci_plat_probe(struct platform_device *pdev) >> if (device_property_read_bool(&pdev->dev, "quirk-broken-port-ped")) >> xhci->quirks |= XHCI_BROKEN_PORT_PED; >> >> + /* imod interval in nanoseconds */ >> + if (device_property_read_u32(sysdev, >> + "imod-interval", &xhci->imod_interval)) >> + xhci->imod_interval = 40000; > > So no matter what value you read, you set it to 40000? Or am I reading > this code incorrectly? I think you may be reading the code incorrectly. device_property_read_u32() returns 0 when the property is found and valid...and stored into xhci->imod_interval. When 0 is returned in this case, the default value of 40,000 is skipped over. If the property is not found, a number of different errors could be returned, but any of them will cause the default value to be used. > There's a good reason putting function calls inside if() is considered a > bad coding style :) I do not disagree with you, however, I was trying to maintain style consistency with the device property reads with the xhci_plat_probe function. If I break that consistency, a couple of ways I might write this cleaner 1) set xhci->imod_interval to 40,000 before the call to device_property_read_u32. If the property exists in a firmware node, it will update the imod_interval value...if it does not exist, it will not update this value and the default will be used. In this case, I would not even check the return value. This method is used quite a bit in the kernel. 2) use a if (device_property_present()) and check to see if that property is even present. If so, call device_property_read_u32() without check return value. This has the downside of still using a function call within the if() which you have already indicated is not your preference. 3) add a retval and test off of this instead of using the function directly in the if() > thanks, > > greg k-h Thanks for taking time to review my patch. I really have no strong preference on how call device_property_read_u32() is tested and I am open to any suggestions. Adam -- Adam Wallis Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
