From mboxrd@z Thu Jan 1 00:00:00 1970 From: vikas Date: Thu, 13 Aug 2015 14:04:59 -0700 Subject: [U-Boot] [v2 2/6] spi: cadence_qspi: remove sram polling from flash read In-Reply-To: <201508132235.28937.marex@denx.de> References: <1437013654-29387-1-git-send-email-vikas.manocha@st.com> <201508131933.12471.marex@denx.de> <55CCF4DD.9010807@st.com> <201508132235.28937.marex@denx.de> Message-ID: <55CD067B.9060808@st.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hi Marek, On 08/13/2015 01:35 PM, Marek Vasut wrote: > On Thursday, August 13, 2015 at 09:49:49 PM, vikas wrote: > > Hi! > >>>> On 08/12/2015 07:09 PM, Marek Vasut wrote: >>>>> On Thursday, July 16, 2015 at 04:27:30 AM, Vikas Manocha wrote: >>>>>> There is no need to check for sram fill level. If sram is empty, cpu >>>>>> will go in the wait state till the time data is available from flash. >>>>> >>>>> Consider the following scenario: >>>>> - CPU core reads some memory area, but there are no data available just >>>>> yet >>>>> >>>>> => CPU core goes into wait state >>>>> >>>>> - The data never arrive >>>>> >>>>> Will the CPU be stuck forever ? If we checked the fill level first >>>>> instead, we would never enter such stuck-state. >>>> >>>> This indirect mode of reading/writing would be entered when the >>>> read/write addresses are in the programmed valid range of addresses. >>>> >>>> Even in case of "data never arrive" scenario, a simple timeout seems >>>> better then currently implemented read sram level with timeout. >>> >>> How do you implement a "simple timeout" if the CPU core is stuck and does >>> not execute instructions ? If you mean interrupt, then forget it, U-Boot >>> does not do interrupts ;-) >> >> Oh yes, you are right. > > So shall we keep the SRAM piece ? Although in this case the better solution would be to have watermark interrupt/status check based on sram fill level, let us keep the existing piece of SRAM. Can we make it configurable (SRAM Level test or not) like from DT or #define ? Rgds, Vikas > > Best regards, > Marek Vasut > . >