From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gururaja Hebbar Subject: Re: [PATCH v4 1/4] ARM: OMAP2+: AM33XX: I2C Sleep/wake sequence support Date: Wed, 21 Aug 2013 13:59:56 +0530 Message-ID: <52147A84.8030704@ti.com> References: <1376432412-8509-1-git-send-email-Russ.Dill@ti.com> <1376432412-8509-2-git-send-email-Russ.Dill@ti.com> <520B595F.2040207@ti.com> <5211B201.2000401@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-omap-owner@vger.kernel.org To: Russ Dill Cc: Kevin Hilman , devicetree@vger.kernel.org, Devicetree Discuss , "linux-omap@vger.kernel.org" , Linux ARM Kernel List List-Id: devicetree@vger.kernel.org On 8/20/2013 10:03 PM, Russ Dill wrote: > On Sun, Aug 18, 2013 at 10:49 PM, Gururaja Hebbar > wrote: >> >> On 8/15/2013 4:04 AM, Russ Dill wrote: >>> On Wed, Aug 14, 2013 at 3:18 AM, Gururaja Hebbar wrote: >>>> On 8/14/2013 3:50 AM, Russ Dill wrote: >>>>> Changes since v1: >>>>> * Rebased onto new am335x PM branch >>>>> * Changed to use 5th param register >> >>>> >> >> [snip] >> [snip] >> >>>>> + >>>>> + wkup_m3_reset_data_pos(); >>>>> + if (am33xx_i2c_sleep_sequence) { >>>>> + pos = wkup_m3_copy_data(am33xx_i2c_sleep_sequence, >>>>> + i2c_sleep_sequence_sz); >>>> >>>> Why do we need to copy this data (same constant data) on every iteration? >>> >>> Because the CM3 firmware is reset after each suspend/resume cycle. The >>> firmware reset handler reinitializes the DMEM. >> >> Well in that why can't the i2c payload be copied to UMEM? >> >> Thanks & regards >> Gururaja >> > > I've given this some thought, and gone back and forth a bit. UMEM is a > bit more complicated because the linker decides what should go where. but linker doesn't know about the copy and the location we are doing at runtime. > Also, it may be that in the future, either the PM for am335x or am43xx > will be writing different sequences depending on the suspend > mode/options. still these info will be coming from DT and can be copied to UMEM. only issue could be space. > > Is there a specific aspect of copying the data each suspend cycle that > you are trying to fix? Is it just that the data could only be copied > once? Or is it the latency of the copy? Copy latency on every iterations is what worries me. it will surely add a delay for suspend. > > Thanks! >