clk/zynq/clkc: Add 'fclk-enable' feature
In some use cases Zynq's FPGA clocks are used as static clock
generators for IP in the FPGA part of the SOC for which no Linux driver
exists and would control those clocks. To avoid automatic
gating of these clocks in such cases a new property - fclk-enable - is
added to the clock controller's DT description to accomodate such use
cases. It's value is a bitmask, where a set bit results in enabling
the corresponding FCLK through the clkc.
FPGA clocks are handled following the rules below:
If an FCLK is not enabled by bootloaders, that FCLK will be disabled in
Linux. Drivers can enable and control it through the CCF as usual.
If an FCLK is enabled by bootloaders AND the corresponding bit in the
'fclk-enable' DT property is set, that FCLK will be enabled by the clkc,
resulting in an off by one reference count for that clock. Ensuring it
will always be running.
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c
index 10772aa..09dd017 100644
--- a/drivers/clk/zynq/clkc.c
+++ b/drivers/clk/zynq/clkc.c
@@ -102,9 +102,10 @@
static void __init zynq_clk_register_fclk(enum zynq_clk fclk,
const char *clk_name, void __iomem *fclk_ctrl_reg,
- const char **parents)
+ const char **parents, int enable)
{
struct clk *clk;
+ u32 enable_reg;
char *mux_name;
char *div0_name;
char *div1_name;
@@ -147,6 +148,12 @@
clks[fclk] = clk_register_gate(NULL, clk_name,
div1_name, CLK_SET_RATE_PARENT, fclk_gate_reg,
0, CLK_GATE_SET_TO_DISABLE, fclk_gate_lock);
+ enable_reg = readl(fclk_gate_reg) & 1;
+ if (enable && !enable_reg) {
+ if (clk_prepare_enable(clks[fclk]))
+ pr_warn("%s: FCLK%u enable failed\n", __func__,
+ fclk - fclk0);
+ }
kfree(mux_name);
kfree(div0_name);
kfree(div1_name);
@@ -213,6 +220,7 @@
int ret;
struct clk *clk;
char *clk_name;
+ unsigned int fclk_enable = 0;
const char *clk_output_name[clk_max];
const char *cpu_parents[4];
const char *periph_parents[4];
@@ -238,6 +246,8 @@
periph_parents[2] = clk_output_name[armpll];
periph_parents[3] = clk_output_name[ddrpll];
+ of_property_read_u32(np, "fclk-enable", &fclk_enable);
+
/* ps_clk */
ret = of_property_read_u32(np, "ps-clk-frequency", &tmp);
if (ret) {
@@ -340,10 +350,12 @@
clk_prepare_enable(clks[dci]);
/* Peripheral clocks */
- for (i = fclk0; i <= fclk3; i++)
+ for (i = fclk0; i <= fclk3; i++) {
+ int enable = !!(fclk_enable & BIT(i - fclk0));
zynq_clk_register_fclk(i, clk_output_name[i],
SLCR_FPGA0_CLK_CTRL + 0x10 * (i - fclk0),
- periph_parents);
+ periph_parents, enable);
+ }
zynq_clk_register_periph_clk(lqspi, 0, clk_output_name[lqspi], NULL,
SLCR_LQSPI_CLK_CTRL, periph_parents, 0);