Message-ID: <CAGETcx9Gnbtt8m+tKZrw6fU_jM1idJ2wJZuz_EyOPq5wpm3Z1w@mail.gmail.com>
Date: Wed, 25 Sep 2024 16:03:22 -0700
From: Saravana Kannan <saravanak@...gle.com>
To: Marek Vasut <marex@...x.de>
Cc: linux-arm-kernel@...ts.infradead.org, kernel@...electronics.com, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Arnd Bergmann <arnd@...db.de>, 
	Fabio Estevam <festevam@...il.com>, Jeff Johnson <quic_jjohnson@...cinc.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Shawn Guo <shawnguo@...nel.org>, imx@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] soc: imx8m: Probe the SoC driver as platform driver

On Wed, Sep 25, 2024 at 3:06 PM Marek Vasut <marex@...x.de> wrote:
>
> With driver_async_probe=* on kernel command line, the following trace is
> produced because on i.MX8M Plus hardware because the soc-imx8m.c driver
> calls of_clk_get_by_name() which returns -EPROBE_DEFER because the clock
> driver is not yet probed. This was not detected during regular testing
> without driver_async_probe.
>
> Convert the SoC code to platform driver and instantiate a platform device
> in its current device_initcall() to probe the platform driver. Rework
> .soc_revision callback to always return valid error code and return SoC
> revision via parameter. This way, if anything in the .soc_revision callback
> return -EPROBE_DEFER, it gets propagated to .probe and the .probe will get
> retried later.

I'm assuming you tested this patch and it works? Did you see any other
issues with driver_async_probe=* ?

Does this improve your probe/boot time? Some stats on that would be nice.

>
> "
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 1 at drivers/soc/imx/soc-imx8m.c:115 imx8mm_soc_revision+0xdc/0x180
> CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.11.0-next-20240924-00002-g2062bb554dea #603
> Hardware name: DH electronics i.MX8M Plus DHCOM Premium Developer Kit (3) (DT)
> pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : imx8mm_soc_revision+0xdc/0x180
> lr : imx8mm_soc_revision+0xd0/0x180
> sp : ffff8000821fbcc0
> x29: ffff8000821fbce0 x28: 0000000000000000 x27: ffff800081810120
> x26: ffff8000818a9970 x25: 0000000000000006 x24: 0000000000824311
> x23: ffff8000817f42c8 x22: ffff0000df8be210 x21: fffffffffffffdfb
> x20: ffff800082780000 x19: 0000000000000001 x18: ffffffffffffffff
> x17: ffff800081fff418 x16: ffff8000823e1000 x15: ffff0000c03b65e8
> x14: ffff0000c00051b0 x13: ffff800082790000 x12: 0000000000000801
> x11: ffff80008278ffff x10: ffff80008209d3a6 x9 : ffff80008062e95c
> x8 : ffff8000821fb9a0 x7 : 0000000000000000 x6 : 00000000000080e3
> x5 : ffff0000df8c03d8 x4 : 0000000000000000 x3 : 0000000000000000
> x2 : 0000000000000000 x1 : fffffffffffffdfb x0 : fffffffffffffdfb
> Call trace:
>  imx8mm_soc_revision+0xdc/0x180
>  imx8_soc_init+0xb0/0x1e0
>  do_one_initcall+0x94/0x1a8
>  kernel_init_freeable+0x240/0x2a8
>  kernel_init+0x28/0x140
>  ret_from_fork+0x10/0x20
> ---[ end trace 0000000000000000 ]---
> SoC: i.MX8MP revision 1.1
> "
>
> Signed-off-by: Marek Vasut <marex@...x.de>
> ---
> Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Fabio Estevam <festevam@...il.com>
> Cc: Jeff Johnson <quic_jjohnson@...cinc.com>
> Cc: Neil Armstrong <neil.armstrong@...aro.org>
> Cc: Pengutronix Kernel Team <kernel@...gutronix.de>
> Cc: Saravana Kannan <saravanak@...gle.com>
> Cc: Sascha Hauer <s.hauer@...gutronix.de>
> Cc: Shawn Guo <shawnguo@...nel.org>
> Cc: imx@...ts.linux.dev
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> ---
> V2: Use the platform device approach instead of late_initcall
> ---
>  drivers/soc/imx/soc-imx8m.c | 92 ++++++++++++++++++++++++++++---------
>  1 file changed, 70 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/soc/imx/soc-imx8m.c b/drivers/soc/imx/soc-imx8m.c
> index fe111bae38c8e..170970d4955c6 100644
> --- a/drivers/soc/imx/soc-imx8m.c
> +++ b/drivers/soc/imx/soc-imx8m.c
> @@ -30,7 +30,7 @@
>
>  struct imx8_soc_data {
>         char *name;
> -       u32 (*soc_revision)(void);
> +       int (*soc_revision)(u32 *socrev);
>  };
>
>  static u64 soc_uid;
> @@ -51,24 +51,29 @@ static u32 imx8mq_soc_revision_from_atf(void)
>  static inline u32 imx8mq_soc_revision_from_atf(void) { return 0; };
>  #endif
>
> -static u32 __init imx8mq_soc_revision(void)
> +static int imx8mq_soc_revision(u32 *socrev)
>  {
>         struct device_node *np;
>         void __iomem *ocotp_base;
>         u32 magic;
>         u32 rev;
>         struct clk *clk;
> +       int ret;
>
>         np = of_find_compatible_node(NULL, NULL, "fsl,imx8mq-ocotp");
>         if (!np)
> -               return 0;
> +               return -EINVAL;
>
>         ocotp_base = of_iomap(np, 0);
> -       WARN_ON(!ocotp_base);
> +       if (!ocotp_base) {
> +               ret = -EINVAL;
> +               goto err_iomap;
> +       }
> +
>         clk = of_clk_get_by_name(np, NULL);
>         if (IS_ERR(clk)) {
> -               WARN_ON(IS_ERR(clk));
> -               return 0;
> +               ret = PTR_ERR(clk);
> +               goto err_clk;
>         }
>
>         clk_prepare_enable(clk);
> @@ -88,32 +93,45 @@ static u32 __init imx8mq_soc_revision(void)
>         soc_uid <<= 32;
>         soc_uid |= readl_relaxed(ocotp_base + OCOTP_UID_LOW);
>
> +       *socrev = rev;
> +
>         clk_disable_unprepare(clk);
>         clk_put(clk);
>         iounmap(ocotp_base);
>         of_node_put(np);
>
> -       return rev;
> +       return 0;
> +
> +err_clk:
> +       iounmap(ocotp_base);
> +err_iomap:
> +       of_node_put(np);
> +       return ret;
>  }
>
> -static void __init imx8mm_soc_uid(void)
> +static int imx8mm_soc_uid(void)
>  {
>         void __iomem *ocotp_base;
>         struct device_node *np;
>         struct clk *clk;
> +       int ret = 0;
>         u32 offset = of_machine_is_compatible("fsl,imx8mp") ?
>                      IMX8MP_OCOTP_UID_OFFSET : 0;
>
>         np = of_find_compatible_node(NULL, NULL, "fsl,imx8mm-ocotp");
>         if (!np)
> -               return;
> +               return -EINVAL;
>
>         ocotp_base = of_iomap(np, 0);
> -       WARN_ON(!ocotp_base);
> +       if (!ocotp_base) {
> +               ret = -EINVAL;
> +               goto err_iomap;
> +       }
> +
>         clk = of_clk_get_by_name(np, NULL);
>         if (IS_ERR(clk)) {
> -               WARN_ON(IS_ERR(clk));
> -               return;
> +               ret = PTR_ERR(clk);
> +               goto err_clk;
>         }
>
>         clk_prepare_enable(clk);
> @@ -124,31 +142,41 @@ static void __init imx8mm_soc_uid(void)
>
>         clk_disable_unprepare(clk);
>         clk_put(clk);
> +
> +err_clk:
>         iounmap(ocotp_base);
> +err_iomap:
>         of_node_put(np);
> +
> +       return ret;
>  }
>
> -static u32 __init imx8mm_soc_revision(void)
> +static int imx8mm_soc_revision(u32 *socrev)
>  {
>         struct device_node *np;
>         void __iomem *anatop_base;
> -       u32 rev;
> +       int ret;
>
>         np = of_find_compatible_node(NULL, NULL, "fsl,imx8mm-anatop");
>         if (!np)
> -               return 0;
> +               return -EINVAL;
>
>         anatop_base = of_iomap(np, 0);
> -       WARN_ON(!anatop_base);
> +       if (!anatop_base) {
> +               ret = -EINVAL;
> +               goto err_iomap;
> +       }
>
> -       rev = readl_relaxed(anatop_base + ANADIG_DIGPROG_IMX8MM);
> +       *socrev = readl_relaxed(anatop_base + ANADIG_DIGPROG_IMX8MM);
>
>         iounmap(anatop_base);
>         of_node_put(np);
>
> -       imx8mm_soc_uid();
> +       return imx8mm_soc_uid();
>
> -       return rev;
> +err_iomap:
> +       of_node_put(np);
> +       return ret;
>  }
>
>  static const struct imx8_soc_data imx8mq_soc_data = {
> @@ -184,7 +212,7 @@ static __maybe_unused const struct of_device_id imx8_soc_match[] = {
>         kasprintf(GFP_KERNEL, "%d.%d", (soc_rev >> 4) & 0xf,  soc_rev & 0xf) : \
>         "unknown"
>
> -static int __init imx8_soc_init(void)
> +static int imx8m_soc_probe(struct platform_device *pdev)
>  {
>         struct soc_device_attribute *soc_dev_attr;
>         struct soc_device *soc_dev;
> @@ -212,8 +240,11 @@ static int __init imx8_soc_init(void)
>         data = id->data;
>         if (data) {
>                 soc_dev_attr->soc_id = data->name;
> -               if (data->soc_revision)
> -                       soc_rev = data->soc_revision();
> +               if (data->soc_revision) {
> +                       ret = data->soc_revision(&soc_rev);
> +                       if (ret)
> +                               goto free_soc;
> +               }
>         }
>
>         soc_dev_attr->revision = imx8_revision(soc_rev);
> @@ -251,6 +282,23 @@ static int __init imx8_soc_init(void)
>         kfree(soc_dev_attr);
>         return ret;
>  }
> +
> +static struct platform_driver imx8m_soc_driver = {
> +       .probe = imx8m_soc_probe,
> +       .driver = {
> +               .name = "imx8m-soc",
> +       },
> +};
> +module_platform_driver(imx8m_soc_driver);

This just translates to a module_init() when compiled as a module.

>
> +
> +static int __init imx8_soc_init(void)
> +{
> +       struct platform_device *pdev;
> +
> +       pdev = platform_device_register_simple("imx8m-soc", -1, NULL, 0);
> +
> +       return IS_ERR(pdev) ? PTR_ERR(pdev) : 0;
> +}
>  device_initcall(imx8_soc_init);

This also translates to a module_init() when compiled as a module.

I've never seen a module with two module_init()s and I'm pretty sure
that doesn't work. I'm guessing this driver doesn't support tristate
in its current state. But with this patch, it should work as a module
too. Why not add support for that too?

Why not just do both of these things in one initcall?
platform_create_bundle() doesn't work with deferred probing though. So
just do one initcall that adds the device and registers the platform
driver.

-Saravana


>  MODULE_DESCRIPTION("NXP i.MX8M SoC driver");
>  MODULE_LICENSE("GPL");
> --
> 2.45.2
>

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