Re: [PATCH v2 3/3] serial: sh-sci: Add support to deassert/assert reset line

Hi Geert,

Thank you for the review.

On Tue, Nov 9, 2021 at 12:58 PM Geert Uytterhoeven [off-list ref] wrote:

Hi Prabhakar,

On Tue, Nov 9, 2021 at 1:17 PM Lad Prabhakar
[off-list ref] wrote:

quoted

On RZ/G2L SoC we need to explicitly deassert the reset line
for the device to work, use this opportunity to deassert/assert
reset line in sh-sci driver.

This patch adds support to read the "resets" property (if available)
from DT and perform deassert/assert when required.

Also, propagate the error to the caller of sci_parse_dt() instead of
returning NULL in case of failure.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
---
v1->v2
* deassert/assert reset line if available on all SoC's
* Updated commit message

Thanks for the update!

quoted

--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c

@@ -37,6 +37,7 @@
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/reset.h>
 #include <linux/scatterlist.h>
 #include <linux/serial.h>
 #include <linux/serial_sci.h>

@@ -3203,23 +3204,53 @@ static const struct of_device_id of_sci_match[] = {
 };
 MODULE_DEVICE_TABLE(of, of_sci_match);

+static void sci_reset_control_assert(void *data)
+{
+       reset_control_assert(data);
+}
+
 static struct plat_sci_port *sci_parse_dt(struct platform_device *pdev,
                                          unsigned int *dev_id)
 {
        struct device_node *np = pdev->dev.of_node;
+       const struct of_device_id *of_id;

Not needed.

Agreed.

quoted

+       struct reset_control *rstc;
        struct plat_sci_port *p;
        struct sci_port *sp;
        const void *data;
-       int id;
+       int id, ret;

        if (!IS_ENABLED(CONFIG_OF) || !np)
-               return NULL;
+               return ERR_PTR(-EINVAL);
+
+       of_id = of_match_device(of_sci_match, &pdev->dev);
+       if (!of_id)
+               return ERR_PTR(-EINVAL);

-       data = of_device_get_match_data(&pdev->dev);

Please keep the old construct using of_device_get_match_data().

OK.

quoted

+       rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
+       if (IS_ERR(rstc)) {
+               dev_err(&pdev->dev, "failed to get reset ctrl %ld\n", PTR_ERR(rstc));
+               return ERR_PTR(PTR_ERR(rstc));

The error might be -EPROBE_DEFER, so please use
"return ERR_PTR(dev_err_probe(...))", to avoid printing the message
in case of probe deferral.

Agreed, will use dev_err_probe().

BTW, ERR_CAST() is a shorthand for ERR_PTR(PTR_ERR()).

Thanks for the pointer.

quoted

+       }
+
+       ret = reset_control_deassert(rstc);
+       if (ret) {
+               dev_err(&pdev->dev, "failed to deassert reset %d\n", ret);
+               return ERR_PTR(ret);
+       }
+
+       ret = devm_add_action_or_reset(&pdev->dev, sci_reset_control_assert, rstc);
+       if (ret) {
+               dev_err(&pdev->dev, "failed to register assert devm action, %d\n",
+                       ret);
+               return ERR_PTR(ret);
+       }
+
+       data = of_id->data;

        p = devm_kzalloc(&pdev->dev, sizeof(struct plat_sci_port), GFP_KERNEL);
        if (!p)
-               return NULL;
+               return ERR_PTR(-ENOMEM);

        /* Get the line number from the aliases node. */
        id = of_alias_get_id(np, "serial");

I gave this a try on Salvator-XS, and noticed no regressions.
I will test this on more SCIF variants later.

Thanks, I will re-spin a v3 just for this lone patch. I hope that's OK.

Cheers,
Prabhakar

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds