Commit 0bc448b4 authored Dec 09, 2019 by Geert Uytterhoeven Committed by Miquel Raynal Jan 27, 2020

mtd: maps: physmap: Add minimal Runtime PM support



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>

parent 2a0b390b

drivers/mtd/maps/physmap-core.c

+15 −5

Original line number	Diff line number	Diff line
		@@ -38,6 +38,7 @@
		#include <linux/mtd/cfi_endian.h>
		#include <linux/io.h>
		#include <linux/of_device.h>
		#include <linux/pm_runtime.h>
		#include <linux/gpio/consumer.h>

		#include "physmap-gemini.h"
		@@ -64,16 +65,16 @@ static int physmap_flash_remove(struct platform_device *dev)
		{
		struct physmap_flash_info *info;
		struct physmap_flash_data *physmap_data;
		int i, err;
		int i, err = 0;

		info = platform_get_drvdata(dev);
		if (!info)
		return 0;
		goto out;

		if (info->cmtd) {
		err = mtd_device_unregister(info->cmtd);
		if (err)
		return err;
		goto out;

		if (info->cmtd != info->mtds[0])
		mtd_concat_destroy(info->cmtd);
		@@ -88,7 +89,10 @@ static int physmap_flash_remove(struct platform_device *dev)
		if (physmap_data && physmap_data->exit)
		physmap_data->exit(dev);

		return 0;
		out:
		pm_runtime_put(&dev->dev);
		pm_runtime_disable(&dev->dev);
		return err;
		}

		static void physmap_set_vpp(struct map_info *map, int state)
		@@ -484,13 +488,19 @@ static int physmap_flash_probe(struct platform_device *dev)
		return -EINVAL;
		}

		pm_runtime_enable(&dev->dev);
		pm_runtime_get_sync(&dev->dev);

		if (dev->dev.of_node)
		err = physmap_flash_of_init(dev);
		else
		err = physmap_flash_pdata_init(dev);

		if (err)
		if (err) {
		pm_runtime_put(&dev->dev);
		pm_runtime_disable(&dev->dev);
		return err;
		}

		for (i = 0; i < info->nmaps; i++) {
		struct resource *res;

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