AM3352: AM3352 u-boot SPI read too slow

Hi Daniel,
I ran a quick test @u-boot prompt with SDK 6.3 on AM335x GP EVM.
I enabled "turbo" mode in MCSPI_CH0CONF register in omap3_spi_read(), see attachment for code change.
The SPI read speed is listed below => ~1.12 MBytes/second

=> sf probe 0
SF: Detected w25q64cv with page size 256 Bytes, erase size 4 KiB, total 8 MiB
=> time sf read ${rdaddr} 0x0 0x800000
device 0 whole chip
SF: 8388608 bytes @ 0x0 Read: OK
time: 7.471 seconds

Best,

-Hong

diff --git a/drivers/spi/omap3_spi.c b/drivers/spi/omap3_spi.c
index c7fcf050a5..8bcf6a6c9d 100644
--- a/drivers/spi/omap3_spi.c
+++ b/drivers/spi/omap3_spi.c
@@ -203,6 +203,7 @@ static int omap3_spi_read(struct omap3_spi_priv *priv, unsigned int len,
 	chconf |= (priv->wordlen - 1) << 7;
 	chconf |= OMAP3_MCSPI_CHCONF_TRM_RX_ONLY;
 	chconf |= OMAP3_MCSPI_CHCONF_FORCE;
+	chconf |= OMAP3_MCSPI_CHCONF_TURBO;
 	omap3_spi_write_chconf(priv, chconf);
 
 	writel(0, &priv->regs->channel[priv->cs].tx);

Hi, I'm the customer

I've tried enable turbo mode, but there is no difference.

=> md 0x4803012C 1
4803012c: 00060000

=> sf probe 0
SF: Detected mx25l25635f with page size 256 Bytes, erase size 64 KiB, total 32 MiB
=> time sf read ${rdaddr} 0x0 0xA00000
device 0 offset 0x0, size 0xa00000
SF: 10485760 bytes @ 0x0 Read: OK

time: 21.088 seconds

The improvement from ~300KB/s to ~500KB/s is due to the deletion of get_timer() calls. (refer to https://e2e.ti.com/support/processors/f/791/t/794109?AM4377-AM4377-uboot-reading-flash-through-spi-is-slow)

I use "counter++ > SPI_WAIT_TIMEOUT" instead of "get_timer(start) > SPI_WAIT_TIMEOUT" to do timeout handling, which improves a lot.

I'm not sure whether this modification will cause side effects. Currently, it works stably.

However, ~500KB/s is not enough. I wish I can reach your speed. (~1.12 MBytes/second is OK!)

I've tried dcache on command, also has no effect.

How can I check my environment is the same as yours?

Thanks!

Best,

Howard

Hi Howard,
For your reference to check MCSPI_CH0CONF register value, I ran another test as listed below.

=> md 0x4803012C 1
4803012c: 00060000                               ....
=> sf probe 0
SF: Detected w25q64cv with page size 256 Bytes, erase size 4 KiB, total 8 MiB
=> md 0x4803012C 1
4803012c: 000913c7                               ....
=> time sf read ${rdaddr} 0x0 0x800000
device 0 whole chip
SF: 8388608 bytes @ 0x0 Read: OK
time: 3.947 seconds
=> md 0x4803012C 1
4803012c: 000913c7    

Please note that:
1. SPI clock is 24MHz as "#define CONFIG_SF_DEFAULT_SPEED 24000000" in "/include/configs/am335x_evm.h"
4803012c: 000913c7 => TURBO mode, CLKG=0 & CLKD=1 => FOUT=48/2=24MHz
2. For testing purpose only, I removed below code snippet from omap3_spi_read() in "drivers/spi/omap3_spi.c" for testing purpose.
==> 2.12 MBytes/s

			if (get_timer(start) > SPI_WAIT_TIMEOUT) {
				printf("SPI RXS timed out, status=0x%08x\n",
					readl(&priv->regs->channel[priv->cs].chstat));
				return -1;
			}

Best,

-Hong

Hi Hong,

Thank you for your reply.

I found that there is something strange.

After sf probe command, the register value (from md command) is still 0x00060000, though I've patched the turbo mode to omap3_spi_read(), and change the SPI speed to 24 MHz.

(We use 48MHz as default speed before.)

#define CONFIG_SF_DEFAULT_SPEED		24000000 // originally 48000000

CNAND:  256 MiB
MMC:
OMAP3_MCSPI_CHCONF=0x001913c7 (0x4803012c)
OMAP3_MCSPI_CHCONF=0x001913c7 (0x4803012c)
OMAP3_MCSPI_CHCONF=0x001913c7 (0x4803012c)
SF: Detected mx25l25635f with page size 256 Bytes, erase size 64 KiB, total 32 MiB
OMAP3_MCSPI_CHCONF=0x001913c7 (0x4803012c)
Net:   cpsw, usb_ether
Hit any key to stop autoboot:  0
=> md 0x4803012C 1
4803012c: 00060000                               ....
=> sf probe 0
OMAP3_MCSPI_CHCONF=0x001913c7 (0x4803012c)
OMAP3_MCSPI_CHCONF=0x001913c7 (0x4803012c)
OMAP3_MCSPI_CHCONF=0x001913c7 (0x4803012c)
SF: Detected mx25l25635f with page size 256 Bytes, erase size 64 KiB, total 32 MiB
=> md 0x4803012C 1
4803012c: 00060000                               ....
=>

However, the printf message in omap3_spi_read() shows that the register value is 0x001913c7.

After further tracing code.

I am not sure whether it is because the spi_release_bus(spi) call in spi_flash_read_common() will reset the register,

and the _omap3_spi_set_mode() call raises OMAP3_MCSPI_CHCONF_IS|OMAP3_MCSPI_CHCONF_DPE1 → 0x60000.

I can't explain why your md commands show 000913c7, but I think the turbo mode has been enabled during reading.

The question is, why the speed is still slow?

Best,

Howard