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Thu, 17 Oct 2019 04:49:15 -0700 (PDT) From: Rasmus Villemoes To: Masahiro Yamada , Andrew Morton , Gao Xiang Subject: [RFC PATCH 3/3] decompress/keepalive.h: add config option for toggling a set of bits Date: Thu, 17 Oct 2019 13:49:06 +0200 Message-Id: <20191017114906.30302-4-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191017114906.30302-1-linux@rasmusvillemoes.dk> References: <20191017114906.30302-1-linux@rasmusvillemoes.dk> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191017_044917_893349_B480770B X-CRM114-Status: GOOD ( 13.55 ) X-Spam-Score: -0.2 (/) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (-0.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2a00:1450:4864:20:0:0:0:242 listed in] [list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kernel@pengutronix.de, Linus Walleij , Rasmus Villemoes , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org It's quite common to have an external watchdog which is serviced via flipping a GPIO, with the value of that GPIO being settable directly in a memory-mapped register. So add kconfig options defining the physical address of such a register as well as a mask to have the decompressor periodically xor into that register. If and when other decompress_keepalive methods are added, this can be made into a "choice DECOMPRESS_KEEPALIVE". Since only LZ4 is wired up currently, this is "depends on KERNEL_LZ4" for now. Also, prevent this option from being shown to the average user. Signed-off-by: Rasmus Villemoes --- include/linux/decompress/keepalive.h | 8 +++++++ init/Kconfig | 33 ++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+) diff --git a/include/linux/decompress/keepalive.h b/include/linux/decompress/keepalive.h index 39caa7693624..c62e49bee7cf 100644 --- a/include/linux/decompress/keepalive.h +++ b/include/linux/decompress/keepalive.h @@ -5,6 +5,14 @@ #ifdef PREBOOT +#ifdef CONFIG_DECOMPRESS_KEEPALIVE_TOGGLE +#define decompress_keepalive() do { \ + long addr = CONFIG_DECOMPRESS_KEEPALIVE_TOGGLE_REG; \ + volatile unsigned *reg = (volatile unsigned *)addr; \ + *reg ^= CONFIG_DECOMPRESS_KEEPALIVE_TOGGLE_MASK; \ +} while (0) +#endif + #endif #ifndef decompress_keepalive diff --git a/init/Kconfig b/init/Kconfig index b4daad2bac23..8a894d9fdd77 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -289,6 +289,39 @@ config KERNEL_UNCOMPRESSED endchoice +config DECOMPRESS_KEEPALIVE_TOGGLE + depends on KERNEL_LZ4 + depends on EXPERT + bool "Toggle some bits while decompressing" + help + Some embedded boards have an always-running hardware + watchdog with a timeout short enough that the board is reset + during decompression, thus preventing the board from ever + booting. + + Enable this to toggle certain bits in a memory register + while decompressing the kernel. This can for example be used + in the common case of an external watchdog serviced via a + memory-mapped GPIO. + + Say N unless you know you need this. + +if DECOMPRESS_KEEPALIVE_TOGGLE + +config DECOMPRESS_KEEPALIVE_TOGGLE_REG + hex "Address of register to modify while decompressing" + help + Set this to a physical address of a 32-bit memory word to + modify while decompressing. + +config DECOMPRESS_KEEPALIVE_TOGGLE_MASK + hex "Bit mask to toggle while decompressing" + help + The register selected above will periodically be xor'ed with + this value during decompression. + +endif + config DEFAULT_HOSTNAME string "Default hostname" default "(none)"