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Geert Uytterhoeven authored
Add minimal runtime PM support (enable on probe, disable on remove), to ensure proper operation with a parent device that uses runtime PM. This is needed on systems where the FLASH is connected to a bus controller that is contained in a PM domain and/or has a gateable functional clock. In such cases, before accessing any device connected to the external bus, the PM domain must be powered up, and/or the functional clock must be enabled, which is typically handled through runtime PM by the bus controller driver. An example of this is the Renesas APE6-EVM development board, which has an Ethernet controller and a CFI FLASH connected to the Bus State Controller (BSC) of an R-Mobile APE6 SoC. As long as the Ethernet driver, which had Runtime PM support since commit 3a611e26 ("net/smsc911x: Add minimal runtime PM support"), keeps the BSC powered, accessing the FLASH works. When the ethernet node in r8a73a4-ape6evm.dts is disabled, the BSC is never powered up, and the kernel crashes when trying to access the FLASH: Unhandled fault: imprecise external abort (0x1406) at 0x00000000 pgd = (ptrval) [00000000] *pgd=7fef2835 Internal error: : 1406 [#1] SMP ARM CPU: 0 PID: 122 Comm: hd Tainted: G W 5.5.0-rc1-ape6evm-00814-g38ca966db25b9dbd-dirty #136 Hardware name: Generic R8A73A4 (Flattened Device Tree) PC is at chip_ready+0x12c/0x380 LR is at chip_ready+0x10c/0x380 Signed-off-by:
Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by:
Miquel Raynal <miquel.raynal@bootlin.com>
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