Re: [PATCH 3/3] serial: sh-sci: Add reset support for RZ/G2L SoC

Hi Geert,

Thank you for the review.

On Mon, Nov 8, 2021 at 4:40 PM Geert Uytterhoeven [off-list ref] wrote:

Hi Prabhakar,

On Wed, Nov 3, 2021 at 6:31 PM Lad Prabhakar
[off-list ref] wrote:

quoted

On RZ/G2L devices should be explicitly pulled out of reset for it
to work. This patch adds support to read the "resets" property and
performs 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>

Thanks for your patch!

quoted

---
Hi Geert,
For handling the resets I was in dual mind whether to perform
reset based on compatible strings or soc-id, let me know your
thoughts. Currently no SoC's use "renesas,sci" so using the same
for performing the reset operation for SCI.

We do, on H8/300.

Missed that.

quoted

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

@@ -3203,23 +3204,58 @@ 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;
        struct plat_sci_port *p;
        struct sci_port *sp;
        const void *data;
        int id;

        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);
+       if (!strcmp(of_id->compatible, "renesas,scif-r9a07g044") ||
+           !strcmp(of_id->compatible, "renesas,sci")) {

This will match on H8/300, too, which doesn't have resets.
Please match against "renesas,sci-r9a07g044" instead.

Please don't use explicit strcmp() calls here, but add a flag to
of_sci_match[].data.

Agreed, does the below hunk look good for handling the reset?

-#define SCI_OF_DATA(type, regtype)     (void *)((type) << 16 | (regtype))
+#define SCIx_RESET                             BIT(31)
+#define SCI_OF_DATA(type, regtype, reset)      (void *)(reset |
(type) << 16 | (regtype))
 #define SCI_OF_TYPE(data)              ((unsigned long)(data) >> 16)
 #define SCI_OF_REGTYPE(data)           ((unsigned long)(data) & 0xffff)

@@ -3169,7 +3170,11 @@ static const struct of_device_id of_sci_match[] = {
        },
        {
                .compatible = "renesas,scif-r9a07g044",
-               .data = SCI_OF_DATA(PORT_SCIF, SCIx_RZ_SCIFA_REGTYPE),
+               .data = SCI_OF_DATA(PORT_SCIF, SCIx_RZ_SCIFA_REGTYPE,

SCIx_RESET),
+       },
+       {
+               .compatible = "renesas,sci-r9a07g044",
+               .data = SCI_OF_DATA(PORT_SCI, SCIx_SCI_REGTYPE, SCIx_RESET),
        },

Cheers,
Prabhakar

quoted

+               struct reset_control *rstc;
+               int ret;
+
+               rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
+               if (IS_ERR(rstc)) {
+                       dev_err(&pdev->dev, "Error: missing reset ctrl\n");
+                       return ERR_PTR(PTR_ERR(rstc));
+               }
+
+               ret = reset_control_deassert(rstc);
+               if (ret) {
+                       dev_err(&pdev->dev, "failed to deassert %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;

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