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ARM OMAP2+ GPMC: calculate GPMCFCLKDIVIDER based on WAITMONITORINGTIME

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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>
This commit is contained in:
Robert ABEL
2015-02-27 16:56:53 +01:00
committed by Roger Quadros
parent f585070b91
commit 2e67690137
5 changed files with 95 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/memory/omap-gpmc.c
+79 -7
View File
@@ -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);