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authorRobert ABEL <rabel@cit-ec.uni-bielefeld.de>2015-02-27 16:56:53 +0100
committerRoger Quadros <rogerq@ti.com>2015-03-06 12:39:48 +0200
commit2e67690137f3a7bac660edd548f8846709c55381 (patch)
tree33262ac06753bd02df92a27fe520f24761dd1847 /drivers/memory
parentf585070b91950a0269eb20f497cceeee0aeefe0e (diff)
downloadlinux-2e67690137f3a7bac660edd548f8846709c55381.tar.bz2
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>
Diffstat (limited to 'drivers/memory')
-rw-r--r--drivers/memory/omap-gpmc.c86
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);