spi_master: modify the error msg a little when over freq limit

The MISO signal will be delayed if the GPIO matrix is enabled.
However, delay also comes from the slave.

Previous code only considers the former case, and assume the frequency
limitations is only violated when GPIO matrix is used.

Now we are able to calculate the freq limit when extenal MISO delay is
given (feature introduced in 9c6c6ec34ab0641ace89aeb9b1a133eb6fae1a18).
The frequency limit is lower when the external MISO delay is large, and
the limit is likely to be violated even with IOMUX.

Resolves https://github.com/espressif/esp-idf/issues/2690.

diff --git a/components/driver/spi_master.c b/components/driver/spi_master.c
index a291825920cad430fae899107e26c88a3a2caee5..7d8932f5e12897c8e40c6e74ff3bed2917e0cfcf 100644 (file)
--- a/components/driver/spi_master.c
+++ b/components/driver/spi_master.c
@@ -442,14 +442,14 @@ esp_err_t spi_bus_add_device(spi_host_device_t host, const spi_device_interface_
     duty_cycle = (dev_config->duty_cycle_pos==0) ? 128 : dev_config->duty_cycle_pos;
     eff_clk = spi_cal_clock(apbclk, dev_config->clock_speed_hz, duty_cycle, (uint32_t*)&clk_reg);
     int freq_limit = spi_get_freq_limit(!(spihost[host]->flags&SPICOMMON_BUSFLAG_NATIVE_PINS), dev_config->input_delay_ns);
-    //GPIO matrix can only change data at 80Mhz rate, which only allows 40MHz SPI clock.
-    SPI_CHECK(eff_clk <= 40*1000*1000 || spihost[host]->flags&SPICOMMON_BUSFLAG_NATIVE_PINS, "80MHz only supported on iomux pins", ESP_ERR_INVALID_ARG);
+
     //Speed >=40MHz over GPIO matrix needs a dummy cycle, but these don't work for full-duplex connections.
     spi_get_timing(!(spihost[host]->flags&SPICOMMON_BUSFLAG_NATIVE_PINS), dev_config->input_delay_ns, eff_clk, &dummy_required, &miso_delay);
     SPI_CHECK( dev_config->flags & SPI_DEVICE_HALFDUPLEX || dummy_required == 0 ||
             dev_config->flags & SPI_DEVICE_NO_DUMMY,
-"When GPIO matrix is used in full-duplex mode at frequency > %.1fMHz, device cannot read correct data.\n\
-Please note the SPI can only work at divisors of 80MHz, and the driver always tries to find the closest frequency to your configuration.\n\
+"When work in full-duplex mode at frequency > %.1fMHz, device cannot read correct data.\n\
+Try to use IOMUX pins to increase the frequency limit, or use the half duplex mode.\n\
+Please note the SPI master can only work at divisors of 80MHz, and the driver always tries to find the closest frequency to your configuration.\n\
 Specify ``SPI_DEVICE_NO_DUMMY`` to ignore this checking. Then you can output data at higher speed, or read data at your own risk.",
             ESP_ERR_INVALID_ARG, freq_limit/1000./1000 );