On Tue, 23 Mar 2021 at 18:53, Jérôme Pouiller
[off-list ref] wrote:

On Tuesday 23 March 2021 15:11:56 CET Ulf Hansson wrote:

quoted

On Mon, 22 Mar 2021 at 18:14, Jérôme Pouiller [off-list ref] wrote:

quoted

On Monday 22 March 2021 13:20:35 CET Ulf Hansson wrote:

quoted

On Mon, 15 Mar 2021 at 14:25, Jerome Pouiller [off-list ref] wrote:

quoted

From: Jérôme Pouiller <jerome.pouiller@silabs.com>

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
---
 drivers/net/wireless/silabs/wfx/bus_sdio.c | 259 +++++++++++++++++++++
 1 file changed, 259 insertions(+)
 create mode 100644 drivers/net/wireless/silabs/wfx/bus_sdio.c

[...]

quoted

+static const struct sdio_device_id wfx_sdio_ids[] = {
+       { SDIO_DEVICE(SDIO_VENDOR_ID_SILABS, SDIO_DEVICE_ID_SILABS_WF200) },
+       { },
+};
+MODULE_DEVICE_TABLE(sdio, wfx_sdio_ids);
+
+struct sdio_driver wfx_sdio_driver = {
+       .name = "wfx-sdio",
+       .id_table = wfx_sdio_ids,
+       .probe = wfx_sdio_probe,
+       .remove = wfx_sdio_remove,
+       .drv = {
+               .owner = THIS_MODULE,
+               .of_match_table = wfx_sdio_of_match,

It's not mandatory to support power management, like system
suspend/resume. However, as this looks like this is a driver for an
embedded SDIO device, you probably want this.

If that is the case, please assign the dev_pm_ops here and implement
the ->suspend|resume() callbacks.

I have no platform to test suspend/resume, so I have only a
theoretical understanding of this subject.

I see.

quoted

I understanding is that with the current implementation, the
device will be powered off on suspend and then totally reset
(including reloading of the firmware) on resume. I am wrong?

You are correct, for a *removable* SDIO card. In this case, the
mmc/sdio core will remove the corresponding SDIO card/device and its
corresponding SDIO func devices at system suspend. It will then be
redetected at system resume (and the SDIO func driver re-probed).

Although, as this is an embedded SDIO device, per definition it's not
a removable card (MMC_CAP_NONREMOVABLE should be set for the
corresponding mmc host), the SDIO card will stick around and instead
the ->suspend|resume() callback needs to be implemented for the SDIO
func driver.

If I follow what has been done in other drivers I would write something
like:

  static int wfx_sdio_suspend(struct device *dev)
  {
          struct sdio_func *func = dev_to_sdio_func(dev);
          struct wfx_sdio_priv *bus = sdio_get_drvdata(func);

          config_reg_write_bits(bus->core, CFG_IRQ_ENABLE_DATA, 0);
          // Necessary to keep device firmware in RAM
          return sdio_set_host_pm_flags(func, MMC_PM_KEEP_POWER);

This will tell the mmc/sdio core to keep the SDIO card powered on
during system suspend. Thus, it doesn't need to re-initialize it at
system resume - and the firmware should not need to be re-programmed.

On the other hand, if you don't plan to support system wakeups, it
would probably be better to power off the card, to avoid wasting
energy while the system is suspended. I assume that means you need to
re-program the firmware as well. Normally, it's these kinds of things
that need to be managed from a ->resume() callback.

  }

However, why not the implementation below?

  static int wfx_sdio_suspend(struct device *dev)
  {
          struct sdio_func *func = dev_to_sdio_func(dev);

          wfx_sdio_remove(func);

I don't know what wfx_sdio_remove() does, but for sure you would need
a ->resume() callback to make it possible to restore power/firmware.

          return 0;
  }

In both cases, I worry to provide these functions without being able to
test them.

Alright, let's simply leave this driver without having the PM
callbacks assigned. I guess we can revisit this at some later point.

The mmc core will log a message about the missing callbacks, in case
someone tries to execute system suspend/resume when the driver has
been probed.

Kind regards
Uffe