[RFC PATCH v2 2/5] mtd: rawnand: gpmi: fix controller timings setting

[Dario Binacchi]

Set the controller registers according to the real clock rate. The
controller registers configuration (setup, hold, timeout, ... cycles)
depends on the clock rate of the GPMI. Using the real rate instead of
the ideal one, avoids that this inaccuracy (required_rate - real_rate)
affects the registers setting.

This patch has been tested on two custom boards with i.MX28 and i.MX6
SOCs:
- i.MX28:
  required rate 100MHz, real rate 99.3MHz
- i.MX6
  required rate 100MHz, real rate 99MHz

Fixes: b1206122069a ("mtd: rawnand: gpmi: use core timings instead of an empirical derivation")
Co-developed-by: Michael Trimarchi <michael at amarulasolutions.com>
Signed-off-by: Michael Trimarchi <michael at amarulasolutions.com>
Signed-off-by: Dario Binacchi <dario.binacchi at amarulasolutions.com>

---

Changes in v2:
- Improve the commit description.
- give examples of frequencies on my setup.

 drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
index 1b64c5a5140d..73c3bf59b55e 100644
--- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
@@ -648,6 +648,7 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this,
 				     const struct nand_sdr_timings *sdr)
 {
 	struct gpmi_nfc_hardware_timing *hw = &this->hw;
+	struct resources *r = &this->resources;
 	unsigned int dll_threshold_ps = this->devdata->max_chain_delay;
 	unsigned int period_ps, reference_period_ps;
 	unsigned int data_setup_cycles, data_hold_cycles, addr_setup_cycles;
@@ -671,6 +672,8 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this,
 		wrn_dly_sel = BV_GPMI_CTRL1_WRN_DLY_SEL_NO_DELAY;
 	}
 
+	hw->clk_rate = clk_round_rate(r->clock[0], hw->clk_rate);
+
 	/* SDR core timings are given in picoseconds */
 	period_ps = div_u64((u64)NSEC_PER_SEC * 1000, hw->clk_rate);
 
-- 
2.32.0