Commit 2ccf80b7 authored Feb 17, 2017 by Valentin Longchamp Committed by Scott Wood Apr 30, 2017

soc/fsl/qe: round brg_freq to 1kHz granularity



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 rounding errors (i.e. 4).

Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
Signed-off-by: Scott Wood <oss@buserror.net>

parent b54ea82f

drivers/soc/fsl/qe/qe.c

+13 −0

Original line number	Diff line number	Diff line
		@@ -161,11 +161,15 @@ EXPORT_SYMBOL(qe_issue_cmd);
		*/
		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;
		@@ -183,6 +187,15 @@ 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);