On Fri, Jul 17, 2015 at 01:20:49PM +0300, Peter De Schrijver wrote: > On Fri, Jul 17, 2015 at 11:57:55AM +0200, Thierry Reding wrote: > > * PGP Signed by an unknown key > > > > On Mon, Jul 13, 2015 at 01:39:40PM +0100, Jon Hunter wrote: > > > The Tegra memory controller implements a flush feature to flush pending > > > accesses and prevent further accesses from occurring. This feature is > > > used when powering down IP blocks to ensure the IP block is in a good > > > state. The flushes are organised by software groups and IP blocks are > > > assigned in hardware to the different software groups. Add helper > > > functions for requesting a handle to an MC flush for a given > > > software group and enabling/disabling the MC flush itself. > > > > > > This is based upon a change by Vince Hsu <vinceh@xxxxxxxxxx>. > > > > > > Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx> > > > --- > > > drivers/memory/tegra/mc.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++ > > > drivers/memory/tegra/mc.h | 2 + > > > include/soc/tegra/mc.h | 34 ++++++++++++++ > > > 3 files changed, 146 insertions(+) > > > > Do we know if this is actually necessary? I remember having a discussion > > with Arnd Bergmann a while ago, and the Linux driver model kind of > > assumes that by the time a device is disabled all outstanding accesses > > will have stopped. > > > > Do we have a way to determine that this even makes a difference? Can we > > trigger a case where not doing this would cause breakage and see that > > adding this fixes that particular issue? > > > > Most likely it is. The memory controller can still be processing requests > when the peripheral domain is powergated. This would mean the response cannot > be delivered in that case. So we need to be sure there are no outstanding > requests before shutting down the domain. My point is that that's the driver's responsibility anyway, hence making the explicit flush unnecessary. Thierry
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