clk: renesas: cpg-mssr: Add missing 1ms delay into reset toggle callback

R-Car V4H Reference Manual R19UH0186EJ0130 Rev.1.30 Apr. 21, 2025 page
583 Figure 9.3.1(a) Software Reset flow (A) as well as flow (B) / (C)
indicate after reset has been asserted by writing a matching reset bit
into register SRCR, it is mandatory to wait 1ms.

This 1ms delay is documented on R-Car V4H and V4M, it is currently
unclear whether S4 is affected as well.  This patch does apply the extra
delay on R-Car S4 as well.

Fix the reset driver to respect the additional delay when toggling
resets.  Drivers which use separate reset_control_(de)assert() must
assure matching delay in their driver code.

Fixes: 0ab55cf18341 ("clk: renesas: cpg-mssr: Add support for R-Car V4H")
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20250918030552.331389-1-marek.vasut+renesas@mailbox.org
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

diff --git a/drivers/clk/renesas/renesas-cpg-mssr.c b/drivers/clk/renesas/renesas-cpg-mssr.c
index de1cf7ba45b78b7f37f6da9faec6fc59c6342c9d..7063d896249eab36fda09c7126e52ba6ed8606a9 100644 (file)
--- a/drivers/clk/renesas/renesas-cpg-mssr.c
+++ b/drivers/clk/renesas/renesas-cpg-mssr.c
@@ -689,8 +689,15 @@ static int cpg_mssr_reset(struct reset_controller_dev *rcdev,
        /* Reset module */
        writel(bitmask, priv->pub.base0 + priv->reset_regs[reg]);
 
-       /* Wait for at least one cycle of the RCLK clock (@ ca. 32 kHz) */
-       udelay(35);
+       /*
+        * On R-Car Gen4, delay after SRCR has been written is 1ms.
+        * On older SoCs, delay after SRCR has been written is 35us
+        * (one cycle of the RCLK clock @ ca. 32 kHz).
+        */
+       if (priv->reg_layout == CLK_REG_LAYOUT_RCAR_GEN4)
+               usleep_range(1000, 2000);
+       else
+               usleep_range(35, 1000);
 
        /* Release module from reset state */
        writel(bitmask, priv->pub.base0 + priv->reset_clear_regs[reg]);