Hi Phil,
On Jum, 2016-11-25 at 14:38 +0000, Phil Edworthy wrote:
The Cadence QSPI controller has specified overheads for the various CS times that are in addition to those programmed in to the Device Delay register. The overheads are different for the delays.
In addition, the existing code does not handle the case when the delay is less than a SCLK period.
This change accurately calculates the additional delays in Ref clocks.
Signed-off-by: Phil Edworthy phil.edworthy@renesas.com
v2: Was "spi: cadence_qspi: Fix CQSPI_CAL_DELAY calculation" Note only did the existing code not cope with the delay less than an SCLK period, but the calculation didn't round properly, and didn't take into account the delays that the QSPI Controller adds to those programmed into the Device Delay reg.
drivers/spi/cadence_qspi_apb.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/drivers/spi/cadence_qspi_apb.c b/drivers/spi/cadence_qspi_apb.c index 1cd636a..56ad952 100644 --- a/drivers/spi/cadence_qspi_apb.c +++ b/drivers/spi/cadence_qspi_apb.c @@ -169,9 +169,6 @@ ((readl(base + CQSPI_REG_CONFIG) >> \ CQSPI_REG_CONFIG_IDLE_LSB) & 0x1)
-#define CQSPI_CAL_DELAY(tdelay_ns, tref_ns, tsclk_ns) \ - ((((tdelay_ns) - (tsclk_ns)) / (tref_ns)))
#define CQSPI_GET_RD_SRAM_LEVEL(reg_base) \ (((readl(reg_base + CQSPI_REG_SDRAMLEVEL)) >> \ CQSPI_REG_SDRAMLEVEL_RD_LSB) & CQSPI_REG_SDRAMLEVEL_RD_MASK) @@ -357,16 +354,20 @@ void cadence_qspi_apb_delay(void *reg_base, cadence_qspi_apb_controller_disable(reg_base);
/* Convert to ns. */ - ref_clk_ns = (1000000000) / ref_clk; + ref_clk_ns = DIV_ROUND_UP(1000000000, ref_clk);
/* Convert to ns. */ - sclk_ns = (1000000000) / sclk_hz;
- /* Plus 1 to round up 1 clock cycle. */ - tshsl = CQSPI_CAL_DELAY(tshsl_ns, ref_clk_ns, sclk_ns) + 1; - tchsh = CQSPI_CAL_DELAY(tchsh_ns, ref_clk_ns, sclk_ns) + 1; - tslch = CQSPI_CAL_DELAY(tslch_ns, ref_clk_ns, sclk_ns) + 1; - tsd2d = CQSPI_CAL_DELAY(tsd2d_ns, ref_clk_ns, sclk_ns) + 1; + sclk_ns = DIV_ROUND_UP(1000000000, sclk_hz);
+ /* The controller adds additional delay to that programmed in the reg */ + if (tshsl_ns >= sclk_ns + ref_clk_ns) + tshsl_ns -= sclk_ns + ref_clk_ns; + if (tchsh_ns >= sclk_ns + 3 * ref_clk_ns) + tchsh_ns -= sclk_ns + 3 * ref_clk_ns;
Any reason we need this? The DIV_ROUND_UP or previous + 1 in algo will ensure its more than a SCLK period.
Thanks Chin Liang
+ tshsl = DIV_ROUND_UP(tshsl_ns, ref_clk_ns); + tchsh = DIV_ROUND_UP(tchsh_ns, ref_clk_ns); + tslch = DIV_ROUND_UP(tslch_ns, ref_clk_ns); + tsd2d = DIV_ROUND_UP(tsd2d_ns, ref_clk_ns);
reg = ((tshsl & CQSPI_REG_DELAY_TSHSL_MASK) << CQSPI_REG_DELAY_TSHSL_LSB); -- 2.7.4
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