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From: John Watts <contact@jookia.org> To: Sascha Hauer <sha@pengutronix.de> Cc: barebox@lists.infradead.org Message-ID: <Y9i2RdNosw238ca1@novena-choice-citizen> References: <20230126185643.104049-1-contact@jookia.org> <20230130102727.GQ13319@pengutronix.de> <Y9efLdQi++e/ZFOn@novena-choice-citizen> <20230130121752.GR13319@pengutronix.de> <Y9e3F2WtTDWOhbE0@novena-choice-citizen> <20230130123142.GS13319@pengutronix.de> <Y9e+dKTG59Y0Kxhl@novena-choice-citizen> <20230130163658.GT13319@pengutronix.de> <Y9gPlWk6pCA6WnQ5@novena-choice-citizen> <20230131061440.GU13319@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230131061440.GU13319@pengutronix.de> X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230130_223419_147483_44AE830E X-CRM114-Status: GOOD ( 16.58 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: <barebox.lists.infradead.org> List-Unsubscribe: <http://lists.infradead.org/mailman/options/barebox>, <mailto:barebox-request@lists.infradead.org?subject=unsubscribe> List-Archive: <http://lists.infradead.org/pipermail/barebox/> List-Post: <mailto:barebox@lists.infradead.org> List-Help: <mailto:barebox-request@lists.infradead.org?subject=help> List-Subscribe: <http://lists.infradead.org/mailman/listinfo/barebox>, <mailto:barebox-request@lists.infradead.org?subject=subscribe> Sender: "barebox" <barebox-bounces@lists.infradead.org> X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.ext.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-4.9 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH] I2C: i.MX: early: Use internal udelay X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.ext.pengutronix.de) On Tue, Jan 31, 2023 at 07:14:40AM +0100, Sascha Hauer wrote: > On Tue, Jan 31, 2023 at 05:42:29AM +1100, John Watts wrote: > > On Mon, Jan 30, 2023 at 05:36:58PM +0100, Sascha Hauer wrote: > > > You can't disable MMU during runtime, but you can compile without MMU > > > support, just disable CONFIG_MMU. However, the early I2C code already > > > runs with MMU disabled, can't you just put in some test code there? > > > > This is going to sound really silly but I'm not sure how to time the code > > without a clock. I guess grabserial? > > You could udelay(10000000) and measure the time with a stopwatch. > That should be accurate enough for this purpose already, in the end > the time will differ anyway between SoCs. > > If you want to measure more exactly we have this little perl script > which prints a timestamp for each line printed. Right I shall try this- though I do wonder if this is a lost cause if the bus clock changes in future i.MX chips. Unless this is specific to the I2C clock. But I was under the assumption the registers aren't dependent on the clock. > Sascha John.