davinci: DA850/OMAP-L138: allow async3 source to be changed

The patch allows Async3 clock source to be selected between PLL1 SYSCLK2
and PLL0 SYSCLK2.

Having Async3 source from PLL1 SYSCLK2 allows peripherals on that
domain to remain unaffected by frequency scaling on PLL0.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/arch/arm/mach-davinci/da850.c b/arch/arm/mach-davinci/da850.c
index f5c3a6a71315..575e9ccbb25f 100644
--- a/arch/arm/mach-davinci/da850.c
+++ b/arch/arm/mach-davinci/da850.c
@@ -30,12 +30,17 @@
 #include "clock.h"
 #include "mux.h"
 
+/* SoC specific clock flags */
+#define DA850_CLK_ASYNC3        BIT(16)
+
 #define DA850_PLL1_BASE         0x01e1a000
 #define DA850_TIMER64P2_BASE    0x01f0c000
 #define DA850_TIMER64P3_BASE    0x01f0d000
 
 #define DA850_REF_FREQ          24000000
 
+#define CFGCHIP3_ASYNC3_CLKSRC  BIT(4)
+
 static struct pll_data pll0_data = {
         .num            = 1,
         .phys_base      = DA8XX_PLL0_BASE,
@@ -232,6 +237,7 @@ static struct clk uart1_clk = {
         .name           = "uart1",
         .parent         = &pll0_sysclk2,
         .lpsc           = DA8XX_LPSC1_UART1,
+        .flags          = DA850_CLK_ASYNC3,
         .psc_ctlr       = 1,
 };
 
@@ -239,6 +245,7 @@ static struct clk uart2_clk = {
         .name           = "uart2",
         .parent         = &pll0_sysclk2,
         .lpsc           = DA8XX_LPSC1_UART2,
+        .flags          = DA850_CLK_ASYNC3,
         .psc_ctlr       = 1,
 };
 
@@ -790,6 +797,30 @@ static struct davinci_timer_info da850_timer_info = {
         .clocksource_id = T0_TOP,
 };
 
+static void da850_set_async3_src(int pllnum)
+{
+        struct clk *clk, *newparent = pllnum ? &pll1_sysclk2 : &pll0_sysclk2;
+        struct davinci_clk *c;
+        unsigned int v;
+        int ret;
+
+        for (c = da850_clks; c->lk.clk; c++) {
+                clk = c->lk.clk;
+                if (clk->flags & DA850_CLK_ASYNC3) {
+                        ret = clk_set_parent(clk, newparent);
+                        WARN(ret, "DA850: unable to re-parent clock %s",
+                                                                clk->name);
+                }
+       }
+
+        v = __raw_readl(DA8XX_SYSCFG_VIRT(DA8XX_CFGCHIP3_REG));
+        if (pllnum)
+                v |= CFGCHIP3_ASYNC3_CLKSRC;
+        else
+                v &= ~CFGCHIP3_ASYNC3_CLKSRC;
+        __raw_writel(v, DA8XX_SYSCFG_VIRT(DA8XX_CFGCHIP3_REG));
+}
+
 static struct davinci_soc_info davinci_soc_info_da850 = {
         .io_desc                = da850_io_desc,
         .io_desc_num            = ARRAY_SIZE(da850_io_desc),
@@ -823,4 +854,13 @@ void __init da850_init(void)
         davinci_soc_info_da850.pinmux_base = DA8XX_SYSCFG_VIRT(0x120);
 
         davinci_common_init(&davinci_soc_info_da850);
+
+        /*
+         * Move the clock source of Async3 domain to PLL1 SYSCLK2.
+         * This helps keeping the peripherals on this domain insulated
+         * from CPU frequency changes caused by DVFS. The firmware sets
+         * both PLL0 and PLL1 to the same frequency so, there should not
+         * be any noticible change even in non-DVFS use cases.
+         */
+        da850_set_async3_src(1);
 }