linux-kernel - [RFC] ARM: omap3: Enable HWMODS for HW Random Number Generator

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Date:   Wed, 28 Aug 2019 10:00:37 -0500
From:   Adam Ford <aford173@...il.com>
To:     linux-omap@...r.kernel.org
Cc:     pali.rohar@...il.com, t-kristo@...com, aaro.koskinen@....fi,
        adam.ford@...icpd.com, Adam Ford <aford173@...il.com>,
        Benoît Cousson <bcousson@...libre.com>,
        Tony Lindgren <tony@...mide.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Paul Walmsley <paul@...an.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [RFC] ARM: omap3: Enable HWMODS for HW Random Number Generator

The datasheet for the AM3517 shows the RNG is connected to L4.
It shows the module address for the RNG is 0x480A0000, and it
matches the omap2.dtsi description.  Since the driver can support
omap2 and omap4, it seems reasonable to assume the omap3 would
use the same core for the RNG.

This RFC, mimics much of the omap2 hwmods on the OMAP3. It
also adds the necessary clock for driving the RNG.  Unfortunately,
it appears non-functional.  If anyone has any suggestions on how
to finish the hwmod (or port it to the newer l4 device tree
format), feedback is requested.

Currently the hwmods repond as follows:

[    0.245697] omap_hwmod: rng: _wait_target_ready failed: -22
[    0.245727] omap_hwmod: rng: cannot be enabled for reset (3)
[    6.780792] omap_hwmod: rng: _wait_target_ready failed: -22

Signed-off-by: Adam Ford <aford173@...il.com>

diff --git a/arch/arm/boot/dts/omap36xx-omap3430es2plus-clocks.dtsi b/arch/arm/boot/dts/omap36xx-omap3430es2plus-clocks.dtsi
index 945537aee3ca..05891dff7fa1 100644
--- a/arch/arm/boot/dts/omap36xx-omap3430es2plus-clocks.dtsi
+++ b/arch/arm/boot/dts/omap36xx-omap3430es2plus-clocks.dtsi
@@ -189,7 +189,7 @@
 			 <&mcspi2_ick>, <&mcspi1_ick>, <&i2c3_ick>, <&i2c2_ick>,
 			 <&i2c1_ick>, <&uart2_ick>, <&uart1_ick>, <&gpt11_ick>,
 			 <&gpt10_ick>, <&mcbsp5_ick>, <&mcbsp1_ick>,
-			 <&omapctrl_ick>, <&aes2_ick>, <&sha12_ick>,
+			 <&omapctrl_ick>, <&aes2_ick>, <&sha12_ick>, <&rng_ick>,
 			 <&ssi_ick>;
 	};
 };
diff --git a/arch/arm/mach-omap2/cm-regbits-34xx.h b/arch/arm/mach-omap2/cm-regbits-34xx.h
index 037529a9e969..82330a66e35c 100644
--- a/arch/arm/mach-omap2/cm-regbits-34xx.h
+++ b/arch/arm/mach-omap2/cm-regbits-34xx.h
@@ -17,6 +17,7 @@
 #define OMAP3430_CLKACTIVITY_IVA2_MASK			(1 << 0)
 #define OMAP3430_CLKTRCTRL_MPU_MASK			(0x3 << 0)
 #define OMAP3430_ST_AES2_SHIFT				28
+#define OMAP34XX_ST_RNG_SHIFT                           2
 #define OMAP3430_ST_SHA12_SHIFT				27
 #define AM35XX_ST_UART4_SHIFT				23
 #define OMAP3430_ST_HDQ_SHIFT				22
diff --git a/arch/arm/mach-omap2/omap_hwmod_3xxx_data.c b/arch/arm/mach-omap2/omap_hwmod_3xxx_data.c
index f52438bdfc14..bae4487383b6 100644
--- a/arch/arm/mach-omap2/omap_hwmod_3xxx_data.c
+++ b/arch/arm/mach-omap2/omap_hwmod_3xxx_data.c
@@ -1627,6 +1627,42 @@ static struct omap_hwmod omap3xxx_gpmc_hwmod = {
 	.flags		= HWMOD_NO_IDLEST | DEBUG_OMAP_GPMC_HWMOD_FLAGS,
 };
 
+/* RNG */
+
+static struct omap_hwmod_class_sysconfig omap3_rng_sysc = {
+	.rev_offs	= 0x3c,
+	.sysc_offs	= 0x40,
+	.syss_offs	= 0x44,
+	.sysc_flags	= (SYSC_HAS_SOFTRESET | SYSC_HAS_AUTOIDLE |
+			   SYSS_HAS_RESET_STATUS),
+	.sysc_fields	= &omap_hwmod_sysc_type1,
+};
+
+static struct omap_hwmod_class omap3_rng_hwmod_class = {
+	.name		= "rng",
+	.sysc		= &omap3_rng_sysc,
+};
+
+struct omap_hwmod omap3xxx_rng_hwmod = {
+	.name		= "rng",
+	.main_clk	= "rng_ick",
+	.prcm		= {
+		.omap2 = {
+			.module_offs = CORE_MOD,
+			.idlest_reg_id = 4,
+			.idlest_idle_bit = OMAP34XX_ST_RNG_SHIFT,
+		},
+	},
+	/*
+	 * XXX The first read from the SYSSTATUS register of the RNG
+	 * after the SYSCONFIG SOFTRESET bit is set triggers an
+	 * imprecise external abort.  It's unclear why this happens.
+	 * Until this is analyzed, skip the IP block reset.
+	 */
+	.flags		= HWMOD_INIT_NO_RESET,
+	.class		= &omap3_rng_hwmod_class,
+};
+
 /*
  * interfaces
  */
@@ -2508,6 +2544,13 @@ static struct omap_hwmod omap3xxx_sham_hwmod = {
 	.class		= &omap3xxx_sham_class,
 };
 
+/* l4_core -> rng */
+struct omap_hwmod_ocp_if omap3xxx_l4_core__rng = {
+	.master		= &omap3xxx_l4_core_hwmod,
+	.slave		= &omap3xxx_rng_hwmod,
+	.clk		= "rng_ick",
+	.user		= OCP_USER_MPU | OCP_USER_SDMA,
+};
 
 static struct omap_hwmod_ocp_if omap3xxx_l4_core__sham = {
 	.master		= &omap3xxx_l4_core_hwmod,
@@ -2769,6 +2812,7 @@ static struct omap_hwmod_ocp_if *omap36xx_hwmod_ocp_ifs[] __initdata = {
 	&omap3xxx_l4_core__mmu_isp,
 	&omap3xxx_l3_main__mmu_iva,
 	&omap3xxx_l4_core__ssi,
+	&omap3xxx_l4_core__rng,
 	NULL,
 };
 
@@ -2788,6 +2832,7 @@ static struct omap_hwmod_ocp_if *am35xx_hwmod_ocp_ifs[] __initdata = {
 	&am35xx_l4_core__mdio,
 	&am35xx_emac__l3,
 	&am35xx_l4_core__emac,
+	&omap3xxx_l4_core__rng,
 	NULL,
 };
 
-- 
2.17.1