[3.19.y-ckt stable] Patch "i2c: mv64xxx: The n clockdiv factor is 0 based on sunxi SoCs" has been added to the 3.19.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    i2c: mv64xxx: The n clockdiv factor is 0 based on sunxi SoCs

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt13.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 203faebcd21f00295988fac031949762dca1cbd1 Mon Sep 17 00:00:00 2001
From: Hans de Goede <hdegoede at redhat.com>
Date: Sun, 27 Sep 2015 16:57:08 +0200
Subject: i2c: mv64xxx: The n clockdiv factor is 0 based on sunxi SoCs
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit bba61f50f76574ca5b84b310925be7c2e8e64275 upstream.

According to the datasheets the n factor for dividing the tclk is
2 to the power n on Allwinner SoCs, not 2 to the power n + 1 as it is
on other mv64xxx implementations.

I've contacted Allwinner about this and they have confirmed that the
datasheet is correct.

This commit fixes the clk-divider calculations for Allwinner SoCs
accordingly.

Signed-off-by: Hans de Goede <hdegoede at redhat.com>
Acked-by: Maxime Ripard <maxime.ripard at free-electrons.com>
Tested-by: Olliver Schinagl <oliver at schinagl.nl>
Signed-off-by: Wolfram Sang <wsa at the-dreams.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/i2c/busses/i2c-mv64xxx.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
index 5801227..43207f5 100644
--- a/drivers/i2c/busses/i2c-mv64xxx.c
+++ b/drivers/i2c/busses/i2c-mv64xxx.c
@@ -146,6 +146,8 @@ struct mv64xxx_i2c_data {
 	bool			errata_delay;
 	struct reset_control	*rstc;
 	bool			irq_clear_inverted;
+	/* Clk div is 2 to the power n, not 2 to the power n + 1 */
+	bool			clk_n_base_0;
 };

 static struct mv64xxx_i2c_regs mv64xxx_i2c_regs_mv64xxx = {
@@ -757,25 +759,29 @@ MODULE_DEVICE_TABLE(of, mv64xxx_i2c_of_match_table);
 #ifdef CONFIG_OF
 #ifdef CONFIG_HAVE_CLK
 static int
-mv64xxx_calc_freq(const int tclk, const int n, const int m)
+mv64xxx_calc_freq(struct mv64xxx_i2c_data *drv_data,
+		  const int tclk, const int n, const int m)
 {
-	return tclk / (10 * (m + 1) * (2 << n));
+	if (drv_data->clk_n_base_0)
+		return tclk / (10 * (m + 1) * (1 << n));
+	else
+		return tclk / (10 * (m + 1) * (2 << n));
 }

 static bool
-mv64xxx_find_baud_factors(const u32 req_freq, const u32 tclk, u32 *best_n,
-			  u32 *best_m)
+mv64xxx_find_baud_factors(struct mv64xxx_i2c_data *drv_data,
+			  const u32 req_freq, const u32 tclk)
 {
 	int freq, delta, best_delta = INT_MAX;
 	int m, n;

 	for (n = 0; n <= 7; n++)
 		for (m = 0; m <= 15; m++) {
-			freq = mv64xxx_calc_freq(tclk, n, m);
+			freq = mv64xxx_calc_freq(drv_data, tclk, n, m);
 			delta = req_freq - freq;
 			if (delta >= 0 && delta < best_delta) {
-				*best_m = m;
-				*best_n = n;
+				drv_data->freq_m = m;
+				drv_data->freq_n = n;
 				best_delta = delta;
 			}
 			if (best_delta == 0)
@@ -813,8 +819,11 @@ mv64xxx_of_config(struct mv64xxx_i2c_data *drv_data,
 	if (of_property_read_u32(np, "clock-frequency", &bus_freq))
 		bus_freq = 100000; /* 100kHz by default */

-	if (!mv64xxx_find_baud_factors(bus_freq, tclk,
-				       &drv_data->freq_n, &drv_data->freq_m)) {
+	if (of_device_is_compatible(np, "allwinner,sun4i-a10-i2c") ||
+	    of_device_is_compatible(np, "allwinner,sun6i-a31-i2c"))
+		drv_data->clk_n_base_0 = true;
+
+	if (!mv64xxx_find_baud_factors(drv_data, bus_freq, tclk)) {
 		rc = -EINVAL;
 		goto out;
 	}
--
1.9.1