On 01/23/2013 02:45 AM, Lucas Stach wrote: > Am Mittwoch, den 23.01.2013, 12:25 +0530 schrieb Venu Byravarasu: >>> -----Original Message----- >>> From: linux-tegra-owner@xxxxxxxxxxxxxxx [mailto:linux-tegra- >>> owner@xxxxxxxxxxxxxxx] On Behalf Of Stephen Warren >>> Sent: Wednesday, January 23, 2013 5:58 AM >>> To: Alan Stern; Greg Kroah-Hartman; Stephen Warren >>> Cc: Venu Byravarasu; linux-tegra@xxxxxxxxxxxxxxx; linux-arm- >>> kernel@xxxxxxxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx; Stephen Warren >>> Subject: [PATCH 1/2] usb: host: tegra: don't touch EMC clock >>> >>> From: Stephen Warren <swarren@xxxxxxxxxx> >>> >>> Clock "emc" is for the External Memory Controller. The USB driver has no >>> business touching this clock directly. Remove the code that does so. >> >> Stephen, >> This was primarily done to make sure that EMC is set to a minimum >> frequency, below which data errors may occur during USB transfers. >> If we plan to remove this, how should we make sure that the EMC >> is programmed for the required frequency during USB transfers? > > You could use something like the API I added in "ARM: tegra: add EMC > clock scaling API". This needs some rework and I looked into integrating > this with the DEVFREQ framework, but I don't think it fits too well. > > Bandwidth requirements should always be communicated to the EMC driver > and not described by clock rates. I agree. Besides, on some boards there's an EMC scaling table defined already, so the EMC driver is simply overriding the value the USB driver selects anyway. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
