[PATCH/RFC net-next] ravb: use clock rate as basis for GTI.TIV

[Simon Horman]

The GTI.TIV may be set to 2GHz^2 / rate, where rate is
that of the clock of the device. Rather than assuming a
rate of 130MHz use the actual rate of the clock.

The motivation for this is to use the correct rate on
the r8a7795/Slavator-X which is advertised as 133MHz but
may differ depending on the extal present on the Slavator-X.

Signed-off-by: Simon Horman 

---
Tested on the topic/gen3-latest branch of Geert Uytterhoeven's
renesas-drivers tree on kernel.org: 3f5a88be9fea ("[WIP] arm64: renesas:
r8a7795: Convert to new CPG/MSSR bindings")
---
 drivers/net/ethernet/renesas/ravb.h  |  3 +++
 drivers/net/ethernet/renesas/ravb_main.c | 35 +++-
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/renesas/ravb.h 
b/drivers/net/ethernet/renesas/ravb.h
index 0623fff932e4..f9dee7436e81 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -576,6 +576,9 @@ enum GTI_BIT {
GTI_TIV = 0x0FFF,
 };
 
+#define GTI_TIV_MAXGTI_TIV
+#define GTI_TIV_MIN0x20
+
 /* GIC */
 enum GIC_BIT {
GIC_PTCE= 0x0001,   /* Undocumented? */
diff --git a/drivers/net/ethernet/renesas/ravb_main.c 
b/drivers/net/ethernet/renesas/ravb_main.c
index 8cc5ec5ed19a..af52c88b8b8f 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1659,6 +1659,37 @@ static const struct of_device_id ravb_match_table[] = {
 };
 MODULE_DEVICE_TABLE(of, ravb_match_table);
 
+static int ravb_set_gti(struct net_device *ndev)
+{
+
+   struct device *dev = ndev->dev.parent;
+   struct device_node *np = dev->of_node;
+   unsigned long long rate;
+   unsigned long inc;
+   struct clk *clk;
+
+   clk = of_clk_get(np, 0);
+   if (IS_ERR(clk)) {
+   dev_err(dev, "could not get clock\n");
+   return PTR_ERR(clk);
+   }
+
+   rate = clk_get_rate(clk);
+   clk_put(clk);
+
+   inc = (10ULL << 20) / rate;
+
+   if (inc < GTI_TIV_MIN || inc > GTI_TIV_MAX) {
+   dev_err(dev, "gti.tiv increment 0x%lx is outside the range 0x%x 
- 0x%x\n",
+   inc, GTI_TIV_MIN, GTI_TIV_MAX);
+   return -EINVAL;
+   }
+
+   ravb_write(ndev, inc, GTI);
+
+   return 0;
+}
+
 static int ravb_probe(struct platform_device *pdev)
 {
struct device_node *np = pdev->dev.of_node;
@@ -1755,7 +1786,9 @@ static int ravb_probe(struct platform_device *pdev)
   CCC);
 
/* Set GTI value */
-   ravb_write(ndev, ((1000 << 20) / 130) & GTI_TIV, GTI);
+   error = ravb_set_gti(ndev);
+   if (error)
+   goto out_release;
 
/* Request GTI loading */
ravb_write(ndev, ravb_read(ndev, GCCR) | GCCR_LTI, GCCR);
-- 
2.1.4

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Re: [PATCH/RFC net-next] ravb: use clock rate as basis for GTI.TIV

[Geert Uytterhoeven]

On Mon, Nov 2, 2015 at 2:40 AM, Simon Horman  wrote:
> The motivation for this is to use the correct rate on
> the r8a7795/Slavator-X which is advertised as 133MHz but

Salvator-X

> may differ depending on the extal present on the Slavator-X.

Salvator-X

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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