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Tue, 21 Apr 2026 01:22:33 -0700 (PDT) From: Debjeet Banerjee To: andy.shevchenko@gmail.com, hansg@kernel.org, mchehab@kernel.org, gregkh@linuxfoundation.org Cc: andy@kernel.org, sakari.ailus@linux.intel.com, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, linux-staging@lists.linux.dev, debjeetbanerjee48@gmail.com Subject: [PATCH v3] media: atomisp: csi2: Fix DPCM decompression for source pad format Date: Tue, 21 Apr 2026 13:52:11 +0530 Message-ID: <20260421082211.74041-1-debjeetbanerjee48@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The CSI2 source pad format was set by blindly copying the sink pad format, regardless of whether the sink pad is receiving a DPCM-compressed mbus code. This was marked with a FIXME comment. When a sensor transmits DPCM-compressed data over MIPI CSI-2 (e.g. MEDIA_BUS_FMT_SGRBG10_DPCM8_1X8), the Atom ISP hardware decompresses it before passing it to the ISP pipeline. Therefore the source pad must expose the uncompressed format (e.g. MEDIA_BUS_FMT_SGRBG10_1X10), not the compressed one. atomisp_subdev_uncompressed_code() already implements this mapping via the compressed_codes[] table in atomisp_subdev.c, which pairs each DPCM mbus code with its uncompressed counterpart. For codes that are not DPCM-compressed, the function returns the code unchanged, so this change is a no-op for all non-DPCM formats. Signed-off-by: Debjeet Banerjee --- v3: - Drop "staging:" prefix in subject (per Andy Shevchenko) v2: - Rebased onto latest media tree (fix CI apply failure) - Fix missing linux-staging recipient (typo in v1) - Fix indentation --- drivers/staging/media/atomisp/pci/atomisp_csi2.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/drivers/staging/media/atomisp/pci/atomisp_csi2.c b/drivers/staging/media/atomisp/pci/atomisp_csi2.c index 95b9113d75e9..e723304bec80 100644 --- a/drivers/staging/media/atomisp/pci/atomisp_csi2.c +++ b/drivers/staging/media/atomisp/pci/atomisp_csi2.c @@ -107,10 +107,17 @@ int atomisp_csi2_set_ffmt(struct v4l2_subdev *sd, &tmp_ffmt); } - /* FIXME: DPCM decompression */ - *actual_ffmt = *ffmt = *__csi2_get_format(csi2, sd_state, which, - CSI2_PAD_SINK); - + /* + * The source pad must expose the uncompressed format even when the sink + * pad receives DPCM-compressed data. The hardware decompresses DPCM + * (e.g. SGRBG10_DPCM8_1X8 -> SGRBG10_1X10) between sink and source, + * so propagate the sink format but map the mbus code to its uncompressed + * equivalent. atomisp_subdev_uncompressed_code() returns the code + * unchanged for formats that are not DPCM-compressed. + */ + *actual_ffmt = *__csi2_get_format(csi2, sd_state, which, CSI2_PAD_SINK); + actual_ffmt->code = atomisp_subdev_uncompressed_code(actual_ffmt->code); + *ffmt = *actual_ffmt; return 0; } -- 2.53.0