serial: sh-sci: Add support to deassert/assert reset line

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.

Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20211110232920.19198-4-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 89ee430..88005d2 100644 (file)
--- 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 +3204,47 @@ 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;
+       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);
 
        data = of_device_get_match_data(&pdev->dev);
 
+       rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
+       if (IS_ERR(rstc))
+               return ERR_PTR(dev_err_probe(&pdev->dev, PTR_ERR(rstc),
+                                            "failed to get reset ctrl\n"));
+
+       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);
+       }
+
        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");
@@ -3227,11 +3252,11 @@ static struct plat_sci_port *sci_parse_dt(struct platform_device *pdev,
                id = ffz(sci_ports_in_use);
        if (id < 0) {
                dev_err(&pdev->dev, "failed to get alias id (%d)\n", id);
-               return NULL;
+               return ERR_PTR(-EINVAL);
        }
        if (id >= ARRAY_SIZE(sci_ports)) {
                dev_err(&pdev->dev, "serial%d out of range\n", id);
-               return NULL;
+               return ERR_PTR(-EINVAL);
        }
 
        sp = &sci_ports[id];
@@ -3318,8 +3343,8 @@ static int sci_probe(struct platform_device *dev)
 
        if (dev->dev.of_node) {
                p = sci_parse_dt(dev, &dev_id);
-               if (p == NULL)
-                       return -EINVAL;
+               if (IS_ERR(p))
+                       return PTR_ERR(p);
        } else {
                p = dev->dev.platform_data;
                if (p == NULL) {