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Piccoli" , Florian Fainelli , Arend van Spriel , William Zhang , bcm-kernel-feedback-list@broadcom.com, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, Kamal Dasu Subject: [PATCH v3 0/4] mmc: Add pstore backend for crash dump storage on eMMC Date: Thu, 19 Mar 2026 14:57:01 -0400 Message-Id: <20260319185705.1516950-1-kamal.dasu@broadcom.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=[UTF-8] Content-Transfer-Encoding: 8bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e This series adds mmcpstore, a pstore backend driver that enables persistent storage of kernel crash logs on eMMC devices. When the kernel panics, pstore captures the kmsg dump and writes it directly to a dedicated MMC partition using polled I/O with interrupts disabled. Changes since v2 (RFC): - Rebased onto v7.0-rc — no longer reverts any existing MMC core or SDHCI changes (v1/v2 accidentally reverted recent upstream commits due to being based on an older tree) - Removed all erase/bitmap tracking logic — MMC/eMMC is managed flash and does not need erase-before-write; the pstore_zone framework handles zone management internally - Uses standard MMC core request path (mmc_start_request) instead of hand-building mmc_request structs; panic-context I/O is handled through proper mmc_host_ops callbacks rather than ad-hoc code in the driver - Added panic-context ops to mmc_host_ops and sdhci_ops for clean separation of panic and normal I/O paths - Fixed deadlocks caused by spinlock contention during panic (lockless mmc_panic_claim_host using WRITE_ONCE) - Fixed data corruption in pstore recovery (zlib_inflate failures) by letting the normal sdhci_request() path run instead of a custom panic request handler - Added PM suspend/resume support with eMMC re-initialization - Supports module loading or builtin loading of the driver - Added MAINTAINERS entry - Split into 4-patch series for reviewability The series is structured as follows: Patch 1 adds panic-context operations to struct mmc_host_ops and a lockless mmc_panic_claim_host() for use during kernel panic when other CPUs are stopped and may hold locks. Patch 2 implements these panic-context operations in the SDHCI host controller driver: draining in-flight requests, polling for completion, and making the command retry path panic-safe. Patch 3 adds mmc_blk_get_card_by_name() helper to look up an mmc_card from a block device name, used by the mmcpstore module path for card discovery. Patch 4 adds the mmcpstore driver itself, which registers with the pstore_blk framework and handles panic writes, PM suspend/resume, and dual-path registration (direct probe hook for builtin, mmc_blk_get_card_by_name() for module). Also adds probe/remove hooks in block.c and declarations in block.h for the builtin path. Tested on Broadcom STB platforms (ARM64) with SDHCI controllers, verified panic dump recovery across multiple panic/reboot cycles with kmsg, pmsg, and console pstore. Previous submissions and related work: RFC v1: https://lore.kernel.org/linux-mmc/20221216212738.7928-1-kdasu.kdev@gmail.com/ RFC v2: https://lore.kernel.org/linux-mmc/20221222185948.12717-1-kdasu.kdev@gmail.com/ Marvell MMC pstore attempt (2020): https://lore.kernel.org/linux-mmc/20201207115753.21728-1-bbudiredla@marvell.com/ pstore/blk documentation: https://www.kernel.org/doc/html/latest/admin-guide/pstore-blk.html Kamal Dasu (4): mmc: core: Add panic-context host operations for pstore backends mmc: sdhci: Implement panic-context write support mmc: block: Add helper to look up mmc_card by device name mmc: core: Add MMC pstore backend driver MAINTAINERS | 6 + drivers/mmc/core/Kconfig | 12 + drivers/mmc/core/Makefile | 1 + drivers/mmc/core/block.c | 56 ++ drivers/mmc/core/block.h | 18 + drivers/mmc/core/core.c | 23 + drivers/mmc/core/mmcpstore.c | 1512 ++++++++++++++++++++++++++++++++++ drivers/mmc/host/sdhci.c | 164 +++- drivers/mmc/host/sdhci.h | 6 + include/linux/mmc/host.h | 12 + 10 files changed, 1806 insertions(+), 4 deletions(-) create mode 100644 drivers/mmc/core/mmcpstore.c -- 2.34.1