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Fri, 15 Aug 2025 12:18:12 +0300 (EEST) Date: Fri, 15 Aug 2025 09:18:13 +0000 From: Sakari Ailus To: Isaac Scott Cc: linux-media@vger.kernel.org, rmfrfs@gmail.com, laurent.pinchart@ideasonboard.com, martink@posteo.de, kernel@puri.sm, mchehab@kernel.org, shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] imx-mipi-csis: Get the number of active lanes from mbus_config Message-ID: References: <20250814113701.165644-1-isaac.scott@ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250814113701.165644-1-isaac.scott@ideasonboard.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250815_021924_207255_8B69E2D3 X-CRM114-Status: GOOD ( 34.29 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Isaac, Thanks for the patch. On Thu, Aug 14, 2025 at 12:37:01PM +0100, Isaac Scott wrote: > Although 4 lanes may be physically available, we may not be using all of > them. Get the number of configured lanes in the case a driver has > implemented the get_mbus_config op. > > Signed-off-by: Isaac Scott > > --- > > Currently, the imx-mipi-csis driver parses the device tree to determine > the number of configured lanes for the CSI receiver. This may be > incorrect in the case that the connected device only uses a subset of > lanes, for example. Allow the drivers for these cameras to create a > mbus_config to configure the number of lanes that are actually being > used. > > If the driver does not support the get_mbus_config op, this patch will > have no functional change. > > Compile tested against media-master (v6.17-rc1) > --- > drivers/media/platform/nxp/imx-mipi-csis.c | 41 ++++++++++++++++++++++ > 1 file changed, 41 insertions(+) > > diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c > index 2beb5f43c2c0..efe4e2ad0382 100644 > --- a/drivers/media/platform/nxp/imx-mipi-csis.c > +++ b/drivers/media/platform/nxp/imx-mipi-csis.c > @@ -939,6 +939,43 @@ static struct mipi_csis_device *sd_to_mipi_csis_device(struct v4l2_subdev *sdev) > return container_of(sdev, struct mipi_csis_device, sd); > } > > +static int mipi_csis_get_active_lanes(struct v4l2_subdev *sd) > +{ > + struct mipi_csis_device *csis = sd_to_mipi_csis_device(sd); > + struct v4l2_mbus_config mbus_config = { 0 }; > + int ret; > + > + ret = v4l2_subdev_call(csis->source.sd, pad, get_mbus_config, > + 0, &mbus_config); > + if (ret == -ENOIOCTLCMD) { > + dev_dbg(csis->dev, "No remote mbus configuration available\n"); > + return 0; > + } > + > + if (ret) { > + dev_err(csis->dev, "Failed to get remote mbus configuration\n"); > + return ret; > + } > + > + if (mbus_config.type != V4L2_MBUS_CSI2_DPHY) { > + dev_err(csis->dev, "Unsupported media bus type %u\n", > + mbus_config.type); > + return -EINVAL; > + } > + > + if (mbus_config.bus.mipi_csi2.num_data_lanes > csis->bus.num_data_lanes) { > + dev_err(csis->dev, > + "Unsupported mbus config: too many data lanes %u\n", > + mbus_config.bus.mipi_csi2.num_data_lanes); > + return -EINVAL; > + } > + > + csis->bus.num_data_lanes = mbus_config.bus.mipi_csi2.num_data_lanes; > + dev_dbg(csis->dev, "Number of lanes: %d\n", csis->bus.num_data_lanes); None of the above is really specific to this driver. Could you instead implement a function that parses the information from the fwnode endpoint and uses mbus configuration on top? The function could take struct media_pad pointer as an argument, or struct v4l2_subdev pointer and the pad number. I wonder if any other parameters could change dynamically but I can't think of that now, so perhaps just the number of lanes is what the function should indeed return. > + > + return 0; > +} > + > static int mipi_csis_s_stream(struct v4l2_subdev *sd, int enable) > { > struct mipi_csis_device *csis = sd_to_mipi_csis_device(sd); > @@ -965,6 +1002,10 @@ static int mipi_csis_s_stream(struct v4l2_subdev *sd, int enable) > format = v4l2_subdev_state_get_format(state, CSIS_PAD_SINK); > csis_fmt = find_csis_format(format->code); > > + ret = mipi_csis_get_active_lanes(sd); > + if (ret < 0) > + dev_dbg(csis->dev, "Failed to get active lanes: %d", ret); > + > ret = mipi_csis_calculate_params(csis, csis_fmt); > if (ret < 0) > goto err_unlock; -- Kind regards, Sakari Ailus