From mboxrd@z Thu Jan 1 00:00:00 1970 From: Philipp Zabel Subject: Re: [PATCH v3 21/24] media: imx: Add MIPI CSI-2 Receiver subdev driver Date: Tue, 31 Jan 2017 10:49:20 +0100 Message-ID: <1485856160.2932.10.camel@pengutronix.de> References: <1483755102-24785-1-git-send-email-steve_longerbeam@mentor.com> <1483755102-24785-22-git-send-email-steve_longerbeam@mentor.com> <20170131000125.GO27312@n2100.armlinux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170131000125.GO27312-l+eeeJia6m9URfEZ8mYm6t73F7V6hmMc@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Russell King - ARM Linux Cc: Steve Longerbeam , robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, mark.rutland-5wv7dgnIgG8@public.gmane.org, shawnguo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org, fabio.estevam-3arQi8VN3Tc@public.gmane.org, mchehab-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, hverkuil-qWit8jRvyhVmR6Xm/wNWPw@public.gmane.org, nick-gcszYUEDH4VrovVCs/uTlw@public.gmane.org, markus.heiser-O6JHGLzbNUwb1SvskN2V4Q@public.gmane.org, laurent.pinchart+renesas-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org, bparrot-l0cyMroinI0@public.gmane.org, geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org, arnd-r2nGTMty4D4@public.gmane.org, sudipm.mukherjee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, minghsiu.tsai-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org, tiffany.lin-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org, jean-christophe.trotin-qxv4g6HH51o@public.gmane.org, horms+renesas-/R6kz+dDXgpPR4JQBCEnsQ@public.gmane.org, niklas.soderlund+renesas-1zkq55x86MTxsAP9Fp7wbw@public.gmane.org, robert.jarzmik-GANU6spQydw@public.gmane.org, songjun.wu-UWL1GkI3JZL3oGB3hsPCZA@public.gmane.org, andrew-ct.chen-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org List-Id: devicetree@vger.kernel.org On Tue, 2017-01-31 at 00:01 +0000, Russell King - ARM Linux wrote: [...] > The iMX6 manuals call for a very specific seven sequence of initialisation > for CSI2, which begins with: > > 1. reset the D-PHY. > 2. place MIPI sensor in LP-11 state > 3. perform D-PHY initialisation > 4. configure CSI2 lanes and de-assert resets and shutdown signals > > Since you reset the CSI2 at power up and then release it, how do you > guarantee that the published sequence is followed? > > With Philipp's driver, this is easy, because there is a prepare_stream > callback which gives the sensor an opportunity to get everything > correctly configured according to the negotiated parameters, and place > the sensor in LP-11 state. > > Some sensors do not power up in LP-11 state, but need to be programmed > fully before being asked to momentarily stream. Only at that point is > the sensor guaranteed to be in the required LP-11 state. Do you expect that 1. and 2. could depend on the negotiated parameters in any way on some hardware? I had removed the prepare_stream callback from my driver in v2 because for my use case at least the above sequence could be realized by 1. in imx-mipi-csi2 s_power(1) 2. in MIPI sensor s_power(1) 3./4. in imx-mipi-csi2 s_stream(1) 4. in MIPI sensor s_stream(1) as long as the sensor is correctly put back into LP-11 in s_stream(0). regards Philipp -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html