Re: [PATCH 3/3] reset: socfpga: add empty driver allowing consumers to probe

On Tue, Oct 5, 2021 at 11:34 AM Philipp Zabel [off-list ref] wrote:

Hi Paweł,

On Mon, 2021-09-20 at 14:41 +0200, Paweł Anikiel wrote:

quoted

The early reset driver doesn't ever probe, which causes consuming
devices to be unable to probe. Add an empty driver to set this device
as available, allowing consumers to probe.

Signed-off-by: Paweł Anikiel <redacted>
---
 drivers/reset/reset-socfpga.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/reset/reset-socfpga.c b/drivers/reset/reset-socfpga.c
index 2a72f861f798..8c6492e5693c 100644
--- a/drivers/reset/reset-socfpga.c
+++ b/drivers/reset/reset-socfpga.c

@@ -92,3 +92,29 @@ void __init socfpga_reset_init(void)
      for_each_matching_node(np, socfpga_early_reset_dt_ids)
              a10_reset_init(np);
 }
+
+/*
+ * The early driver is problematic, because it doesn't register
+ * itself as a driver. This causes certain device links to prevent
+ * consumer devices from probing. The hacky solution is to register
+ * an empty driver, whose only job is to attach itself to the reset
+ * manager and call probe.
+ */
+static const struct of_device_id socfpga_reset_dt_ids[] = {
+     { .compatible = "altr,rst-mgr", },
+     { /* sentinel */ },
+};
+
+static int reset_simple_probe(struct platform_device *pdev)
+{
+     return 0;
+}
+
+static struct platform_driver reset_socfpga_driver = {
+     .probe  = reset_simple_probe,
+     .driver = {
+             .name           = "socfpga-reset",
+             .of_match_table = socfpga_reset_dt_ids,
+     },
+};
+builtin_platform_driver(reset_socfpga_driver);

If we can just let devlink delay all consumers until the empty driver is
probed, does the reset controller have to be registered early at all?

regards
Philipp

I asked Dinh if the reset controller code needs to be called early:

That's correct. It's for one of the SP timers.

On 9/16/21 6:13 AM, Paweł Anikiel wrote:

quoted

Hi,

I would like to ask you about the following commit:

quoted

commit b3ca9888f35fa6919569cf27c929dc0ac49e9716
Author: Dinh Nguyen [off-list ref]
Date:   Tue Nov 13 12:50:48 2018 -0600

     reset: socfpga: add an early reset driver for SoCFPGA

     Create a separate reset driver that uses the reset operations in
     reset-simple. The reset driver for the SoCFPGA platform needs to
     register early in order to be able bring online timers that needed
     early in the kernel bootup.
     [...]

Which online timers is this commit message referring to? I couldn't find
any information about this. Without this patch the kernel seems to work
fine on an Arria 10 (with Mercury AA1 module). What's the exact reason
a regular platform driver isn't sufficient?

Best regards,
Paweł

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