This is a note to let you know that I've just added the patch titled
soc/fsl/qe: round brg_freq to 1kHz granularity
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
soc-fsl-qe-round-brg_freq-to-1khz-granularity.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Mar 22 14:40:23 CET 2018
From: Valentin Longchamp <valentin.longchamp@xxxxxxxxxxx>
Date: Fri, 17 Feb 2017 11:29:45 +0100
Subject: soc/fsl/qe: round brg_freq to 1kHz granularity
From: Valentin Longchamp <valentin.longchamp@xxxxxxxxxxx>
[ Upstream commit 2ccf80b7566cc035d903dd0ac5d7ebd25c2c1060 ]
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@xxxxxxxxxxx>
Signed-off-by: Scott Wood <oss@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/soc/fsl/qe/qe.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
--- a/drivers/soc/fsl/qe/qe.c
+++ b/drivers/soc/fsl/qe/qe.c
@@ -163,11 +163,15 @@ 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;
@@ -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);
Patches currently in stable-queue which might be from valentin.longchamp@xxxxxxxxxxx are
queue-4.9/soc-fsl-qe-round-brg_freq-to-1khz-granularity.patch