[PATCH RFC] Specifying default-disabled devices
Zev Weiss
zweiss at equinix.com
Tue Sep 21 12:56:28 AEST 2021
On Fri, Sep 10, 2021 at 02:59:45PM PDT, Zev Weiss wrote:
>>>Well, I'm aiming to be able to use a dts fragment looking something
>>>like (on an ast2500):
>>>
>>> &spi1 {
>>> status = "reserved";
>>> pinctrl-names = "default";
>>> pinctrl-0 = <&pinctrl_spi1_default>;
>>> flash at 0 {
>>> status = "okay";
>>> label = "bios";
>>> m25p,fast-read;
>>> };
>>> };
>>
>>[do you want just the flash node to be reserved, or the entire
>>controller? I assume the controller is always available...]
>>
>
>The flash node would make more sense, but thus far with my noautobind
>argument I've been doing it at the spi1 controller level because I don't
>know of a way to do the runtime attach/detach of individual flash
>devices behind the controller (the analog of doing the driver bind via
>sysfs), and from a glance at the aspeed-smc driver it doesn't look like
>there is one (the aspeed_smc_setup_flash() call in the controller's
>probe path seems to be the only path to instantiating any child
>devices).
>
Pursuing this angle a bit, however, I now have the below patch which
enables attaching & detaching individual flash chips behind an
aspeed-smc controller at runtime (via sysfs).
This has the downside of burying 'status = "reserved"' support in a
piece of somewhat niche functionality in one specific driver, rather
than for DT devices in general (though after investigating a bit, it
looks like even adding driver-core support would only cover devices that
get drivers bound, e.g. the aspeed-smc controller itself, and not any
child devices further down the tree, like individual flash chips).
That aside though, this seems to solve my problem in a fairly clean,
non-invasive manner that shouldn't cause any compatibility problems
elsewhere, which is appealing...a viable approach perhaps?
Zev
>From b17ad478b9d2e8357461412f9d5d734a8ad8df0b Mon Sep 17 00:00:00 2001
From: Zev Weiss <zev at bewilderbeest.net>
Date: Fri, 17 Sep 2021 17:03:18 -0500
Subject: [PATCH] mtd: spi-nor: aspeed: make flash chips runtime
attachable/detachable
There are now two new sysfs attributes, attach_chip and detach_chip,
into which a chip select number can be written to attach or detach the
corresponding chip. Chips marked with a DT status of "reserved" are
left detached initially and can be attached on demand by userspace via
attach_chip.
Signed-off-by: Zev Weiss <zev at bewilderbeest.net>
---
drivers/mtd/spi-nor/controllers/aspeed-smc.c | 166 +++++++++++++++----
1 file changed, 138 insertions(+), 28 deletions(-)
diff --git a/drivers/mtd/spi-nor/controllers/aspeed-smc.c b/drivers/mtd/spi-nor/controllers/aspeed-smc.c
index c421fad4b3f5..db7cc8d2f4d0 100644
--- a/drivers/mtd/spi-nor/controllers/aspeed-smc.c
+++ b/drivers/mtd/spi-nor/controllers/aspeed-smc.c
@@ -190,6 +190,7 @@ struct aspeed_smc_controller;
struct aspeed_smc_chip {
int cs;
+ bool attached;
struct aspeed_smc_controller *controller;
void __iomem *ctl; /* control register */
void __iomem *ahb_base; /* base of chip window */
@@ -207,12 +208,13 @@ struct aspeed_smc_controller {
const struct aspeed_smc_info *info; /* type info of controller */
void __iomem *regs; /* controller registers */
void __iomem *ahb_base; /* per-chip window resource */
+ struct resource *ahb_res; /* resource for AHB address space */
u32 ahb_base_phy; /* phys addr of AHB window */
u32 ahb_window_size; /* full mapping window size */
unsigned long clk_frequency;
- struct aspeed_smc_chip *chips[]; /* pointers to attached chips */
+ struct aspeed_smc_chip *chips[]; /* pointers to connected chips */
};
#define ASPEED_SPI_DEFAULT_FREQ 50000000
@@ -619,15 +621,27 @@ static ssize_t aspeed_smc_read(struct spi_nor *nor, loff_t from, size_t len,
return len;
}
+static int aspeed_smc_unregister_chip(struct aspeed_smc_chip *chip)
+{
+ int ret = mtd_device_unregister(&chip->nor.mtd);
+ if (!ret)
+ chip->attached = false;
+ return ret;
+}
+
static int aspeed_smc_unregister(struct aspeed_smc_controller *controller)
{
struct aspeed_smc_chip *chip;
- int n;
+ int n, ret;
for (n = 0; n < controller->info->nce; n++) {
chip = controller->chips[n];
- if (chip)
- mtd_device_unregister(&chip->nor.mtd);
+ if (chip && chip->attached) {
+ ret = aspeed_smc_unregister_chip(chip);
+ if (ret)
+ dev_warn(controller->dev, "failed to unregister CS%d: %d\n",
+ n, ret);
+ }
}
return 0;
@@ -1232,25 +1246,57 @@ static const struct spi_nor_controller_ops aspeed_smc_controller_ops = {
.write = aspeed_smc_write_user,
};
-static int aspeed_smc_setup_flash(struct aspeed_smc_controller *controller,
- struct device_node *np, struct resource *r)
+static int aspeed_smc_register_chip(struct aspeed_smc_chip *chip)
{
- const struct spi_nor_hwcaps hwcaps = {
+ static const struct spi_nor_hwcaps hwcaps = {
.mask = SNOR_HWCAPS_READ |
SNOR_HWCAPS_READ_FAST |
SNOR_HWCAPS_READ_1_1_2 |
SNOR_HWCAPS_PP,
};
+ int ret;
+
+ ret = aspeed_smc_chip_setup_init(chip, chip->controller->ahb_res);
+ if (ret)
+ return ret;
+
+ /*
+ * TODO: Add support for Dual and Quad SPI protocols attach when board
+ * support is present as determined by of property.
+ */
+ ret = spi_nor_scan(&chip->nor, NULL, &hwcaps);
+ if (ret)
+ return ret;
+
+ ret = aspeed_smc_chip_setup_finish(chip);
+ if (ret)
+ return ret;
+
+ ret = mtd_device_register(&chip->nor.mtd, NULL, 0);
+ if (ret)
+ return ret;
+
+ chip->attached = true;
+
+ return 0;
+}
+
+static int aspeed_smc_setup_flash(struct aspeed_smc_controller *controller,
+ struct device_node *np, struct resource *r)
+{
const struct aspeed_smc_info *info = controller->info;
struct device *dev = controller->dev;
struct device_node *child;
unsigned int cs;
int ret = -ENODEV;
- for_each_available_child_of_node(np, child) {
+ for_each_child_of_node(np, child) {
struct aspeed_smc_chip *chip;
struct spi_nor *nor;
- struct mtd_info *mtd;
+
+ /* Skip disabled nodes, but include reserved ones for later attachment */
+ if (!of_device_is_available(child) && !of_device_is_reserved(child))
+ continue;
/* This driver does not support NAND or NOR flash devices. */
if (!of_device_is_compatible(child, "jedec,spi-nor"))
@@ -1294,35 +1340,20 @@ static int aspeed_smc_setup_flash(struct aspeed_smc_controller *controller,
chip->cs = cs;
nor = &chip->nor;
- mtd = &nor->mtd;
nor->dev = dev;
nor->priv = chip;
spi_nor_set_flash_node(nor, child);
nor->controller_ops = &aspeed_smc_controller_ops;
- ret = aspeed_smc_chip_setup_init(chip, r);
- if (ret)
- break;
-
- /*
- * TODO: Add support for Dual and Quad SPI protocols
- * attach when board support is present as determined
- * by of property.
- */
- ret = spi_nor_scan(nor, NULL, &hwcaps);
- if (ret)
- break;
+ controller->chips[cs] = chip;
- ret = aspeed_smc_chip_setup_finish(chip);
- if (ret)
- break;
+ if (of_device_is_reserved(child))
+ continue;
- ret = mtd_device_register(mtd, NULL, 0);
+ ret = aspeed_smc_register_chip(chip);
if (ret)
break;
-
- controller->chips[cs] = chip;
}
if (ret) {
@@ -1333,6 +1364,78 @@ static int aspeed_smc_setup_flash(struct aspeed_smc_controller *controller,
return ret;
}
+static inline struct aspeed_smc_controller *to_aspeed_smc_controller(struct device *dev)
+{
+ struct platform_device *pdev = container_of(dev, struct platform_device, dev);
+ return platform_get_drvdata(pdev);
+}
+
+static ssize_t attach_chip_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned long cs;
+ struct aspeed_smc_controller *controller;
+ struct aspeed_smc_chip *chip;
+ ssize_t ret = kstrtoul(buf, 0, &cs);
+ if (ret)
+ return ret;
+
+ controller = to_aspeed_smc_controller(dev);
+ if (cs >= controller->info->nce)
+ return -EINVAL;
+
+ chip = controller->chips[cs];
+
+ if (!chip)
+ return -ENODEV;
+
+ if (chip->attached)
+ return -EEXIST;
+
+ ret = aspeed_smc_register_chip(chip);
+
+ return ret ? ret : count;
+}
+static DEVICE_ATTR_WO(attach_chip);
+
+static ssize_t detach_chip_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned long cs;
+ struct aspeed_smc_controller *controller;
+ struct aspeed_smc_chip *chip;
+ ssize_t ret = kstrtoul(buf, 0, &cs);
+ if (ret)
+ return ret;
+
+ controller = to_aspeed_smc_controller(dev);
+ if (cs >= controller->info->nce)
+ return -EINVAL;
+
+ chip = controller->chips[cs];
+
+ if (!chip)
+ return -ENODEV;
+
+ if (!chip->attached)
+ return -ENOENT;
+
+ ret = aspeed_smc_unregister_chip(chip);
+
+ return ret ? ret : count;
+}
+static DEVICE_ATTR_WO(detach_chip);
+
+static struct attribute *aspeed_smc_sysfs_attrs[] = {
+ &dev_attr_attach_chip.attr,
+ &dev_attr_detach_chip.attr,
+ NULL,
+};
+
+static const struct attribute_group aspeed_smc_sysfs_attr_group = {
+ .attrs = aspeed_smc_sysfs_attrs,
+};
+
static int aspeed_smc_probe(struct platform_device *pdev)
{
struct device_node *np = pdev->dev.of_node;
@@ -1357,6 +1460,12 @@ static int aspeed_smc_probe(struct platform_device *pdev)
controller->info = info;
controller->dev = dev;
+ ret = devm_device_add_group(dev, &aspeed_smc_sysfs_attr_group);
+ if (ret) {
+ dev_err(dev, "Failed to create sysfs files\n");
+ return ret;
+ }
+
mutex_init(&controller->mutex);
platform_set_drvdata(pdev, controller);
@@ -1366,6 +1475,7 @@ static int aspeed_smc_probe(struct platform_device *pdev)
return PTR_ERR(controller->regs);
res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+ controller->ahb_res = res;
controller->ahb_base_phy = res->start;
controller->ahb_base = devm_ioremap_resource(dev, res);
if (IS_ERR(controller->ahb_base))
--
2.33.0
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