Because of integer computation rounding in u-boot (that sets the QE
brg-frequency DTS prop), the clk value is 99999999 Hz even though it is
100 MHz.
When setting brg clks that are exact divisors of 100 MHz, this small
differnce plays a role and can result in lower clks to be output (for
instance 20 MHz - divide by 5 - results in 16.666 MHz - divide by 6).
This patch fixes that by "forcing" the brg_clk to the nearest kHz when
the difference is below 2 integer rouding errors (i.e. 4).
Signed-off-by: Valentin Longchamp <valentin.longch...@keymile.com>
---
drivers/soc/fsl/qe/qe.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/soc/fsl/qe/qe.c b/drivers/soc/fsl/qe/qe.c
index ade168f..03874df 100644
--- a/drivers/soc/fsl/qe/qe.c
+++ b/drivers/soc/fsl/qe/qe.c
@@ -163,11 +163,15 @@ int qe_issue_cmd(u32 cmd, u32 device, u8 mcn_protocol,
u32 cmd_input)
*/
static unsigned int brg_clk = 0;
+#define CLK_GRAN (1000)
+#define CLK_GRAN_LIMIT (5)
+
unsigned int qe_get_brg_clk(void)
{
struct device_node *qe;
int size;
const u32 *prop;
+ unsigned int mod;
if (brg_clk)
return brg_clk;
@@ -185,6 +189,15 @@ unsigned int qe_get_brg_clk(void)
of_node_put(qe);
+ /* round this if near to a multiple of CLK_GRAN */
+ mod = brg_clk % CLK_GRAN;
+ if (mod) {
+ if (mod < CLK_GRAN_LIMIT)
+ brg_clk -= mod;
+ else if (mod > (CLK_GRAN - CLK_GRAN_LIMIT))
+ brg_clk += CLK_GRAN - mod;
+ }
+
return brg_clk;
}
EXPORT_SYMBOL(qe_get_brg_clk);
--
1.8.3.1
