ARM OMAP2+ GPMC: calculate GPMCFCLKDIVIDER based on WAITMONITORINGTIME

The WAITMONITORINGTIME is expressed as a number of GPMC_CLK clock cycles,
even though the access is defined as asynchronous, and no GPMC_CLK clock
is provided to the external device. Still, GPMCFCLKDIVIDER is used as a divider
for the GPMC clock, so it must be programmed to define the
correct WAITMONITORINGTIME delay.

Calculate GPMCFCLKDIVIDER independent of gpmc,sync-clk-ps in DT for
pure asynchronous accesses, i.e. both read and write asynchronous.

Signed-off-by: Robert ABEL <rabel@cit-ec.uni-bielefeld.de>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>

1 files changed, 79 insertions, 7 deletions

diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
index 5c36ff397b73..768bab233196 100644
--- a/drivers/memory/omap-gpmc.c
+++ b/drivers/memory/omap-gpmc.c
@@ -138,7 +138,9 @@
 #define GPMC_CONFIG1_PAGE_LEN(val)      ((val & 3) << 23)
 #define GPMC_CONFIG1_WAIT_READ_MON      (1 << 22)
 #define GPMC_CONFIG1_WAIT_WRITE_MON     (1 << 21)
-#define GPMC_CONFIG1_WAIT_MON_IIME(val) ((val & 3) << 18)
+#define GPMC_CONFIG1_WAIT_MON_TIME(val) ((val & 3) << 18)
+/** WAITMONITORINGTIME Max Ticks */
+#define GPMC_CONFIG1_WAITMONITORINGTIME_MAX  2
 #define GPMC_CONFIG1_WAIT_PIN_SEL(val)  ((val & 3) << 16)
 #define GPMC_CONFIG1_DEVICESIZE(val)    ((val & 3) << 12)
 #define GPMC_CONFIG1_DEVICESIZE_16      GPMC_CONFIG1_DEVICESIZE(1)
@@ -525,13 +527,48 @@ static int set_gpmc_timing_reg(int cs, int reg, int st_bit, int end_bit,
                         t->field, #field) < 0)                  \
                 return -1
 
+/**
+ * gpmc_calc_waitmonitoring_divider - calculate proper GPMCFCLKDIVIDER based on WAITMONITORINGTIME
+ * WAITMONITORINGTIME will be _at least_ as long as desired, i.e.
+ * read  --> don't sample bus too early
+ * write --> data is longer on bus
+ *
+ * Formula:
+ * gpmc_clk_div + 1 = ceil(ceil(waitmonitoringtime_ns / gpmc_fclk_ns)
+ *                    / waitmonitoring_ticks)
+ * WAITMONITORINGTIME resulting in 0 or 1 tick with div = 1 are caught by
+ * div <= 0 check.
+ *
+ * @wait_monitoring: WAITMONITORINGTIME in ns.
+ * @return:          -1 on failure to scale, else proper divider > 0.
+ */
+static int gpmc_calc_waitmonitoring_divider(unsigned int wait_monitoring)
+{
+
+        int div = gpmc_ns_to_ticks(wait_monitoring);
+
+        div += GPMC_CONFIG1_WAITMONITORINGTIME_MAX - 1;
+        div /= GPMC_CONFIG1_WAITMONITORINGTIME_MAX;
+
+        if (div > 4)
+                return -1;
+        if (div <= 0)
+                div = 1;
+
+        return div;
+
+}
+
+/**
+ * gpmc_calc_divider - calculate GPMC_FCLK divider for sync_clk GPMC_CLK period.
+ * @sync_clk: GPMC_CLK period in ps.
+ * @return:   Returns at least 1 if GPMC_FCLK can be divided to GPMC_CLK.
+ *            Else, returns -1.
+ */
 int gpmc_calc_divider(unsigned int sync_clk)
 {
-        int div;
-        u32 l;
+        int div = gpmc_ps_to_ticks(sync_clk);
 
-        l = sync_clk + (gpmc_get_fclk_period() - 1);
-        div = l / gpmc_get_fclk_period();
         if (div > 4)
                 return -1;
         if (div <= 0)
@@ -540,7 +577,15 @@ int gpmc_calc_divider(unsigned int sync_clk)
         return div;
 }
 
-int gpmc_cs_set_timings(int cs, const struct gpmc_timings *t)
+/**
+ * gpmc_cs_set_timings - program timing parameters for Chip Select Region.
+ * @cs:     Chip Select Region.
+ * @t:      GPMC timing parameters.
+ * @s:      GPMC timing settings.
+ * @return: 0 on success, -1 on error.
+ */
+int gpmc_cs_set_timings(int cs, const struct gpmc_timings *t,
+                        const struct gpmc_settings *s)
 {
         int div;
         u32 l;
@@ -550,6 +595,33 @@ int gpmc_cs_set_timings(int cs, const struct gpmc_timings *t)
         if (div < 0)
                 return div;
 
+        /*
+         * See if we need to change the divider for waitmonitoringtime.
+         *
+         * Calculate GPMCFCLKDIVIDER independent of gpmc,sync-clk-ps in DT for
+         * pure asynchronous accesses, i.e. both read and write asynchronous.
+         * However, only do so if WAITMONITORINGTIME is actually used, i.e.
+         * either WAITREADMONITORING or WAITWRITEMONITORING is set.
+         *
+         * This statement must not change div to scale async WAITMONITORINGTIME
+         * to protect mixed synchronous and asynchronous accesses.
+         *
+         * We raise an error later if WAITMONITORINGTIME does not fit.
+         */
+        if (!s->sync_read && !s->sync_write &&
+            (s->wait_on_read || s->wait_on_write)
+           ) {
+
+                div = gpmc_calc_waitmonitoring_divider(t->wait_monitoring);
+                if (div < 0) {
+                        pr_err("%s: waitmonitoringtime %3d ns too large for greatest gpmcfclkdivider.\n",
+                               __func__,
+                               t->wait_monitoring
+                               );
+                        return -1;
+                }
+        }
+
         GPMC_SET_ONE(GPMC_CS_CONFIG2,  0,  3, cs_on);
         GPMC_SET_ONE(GPMC_CS_CONFIG2,  8, 12, cs_rd_off);
         GPMC_SET_ONE(GPMC_CS_CONFIG2, 16, 20, cs_wr_off);
@@ -1810,7 +1882,7 @@ static int gpmc_probe_generic_child(struct platform_device *pdev,
         if (ret < 0)
                 goto err;
 
-        ret = gpmc_cs_set_timings(cs, &gpmc_t);
+        ret = gpmc_cs_set_timings(cs, &gpmc_t, &gpmc_s);
         if (ret) {
                 dev_err(&pdev->dev, "failed to set gpmc timings for: %s\n",
                         child->name);