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Our ext flash has a rather peculiar 'feature' in that SPI sometimes locks up when first accessing the ext flash. Resetting the flash chip prior alleviates this problem. This is highly specific and I don't expect this to make it into wolfboot as is, but I'm hopeful we can come to some sort of solution where we don't need to patch every new wolfboot version.
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🟡 Changes recommended
Unresolved SPI flash transaction and reset-sequencing defects can hang boot, prevent reset recovery, and produce incorrect JEDEC IDs.
4 open issues
What changed in this PR
This PR adds an optional software reset during external SPI flash probing to address reported first-access lockups without requiring downstream patches.
Changes:
- Defines reset-enable (
0x66) and reset (0x99) commands. - Adds a
RESET_EXT_FLASH-guarded reset sequence and delay loops. - Changes the device-identification transaction around the reset option.
| File | Description |
|---|---|
src/spi_flash.c |
Adds optional flash reset handling and modifies probe sequencing. |
Review effort: Balanced
| @@ -186,9 +188,28 @@ uint16_t spi_flash_probe(void) | |||
| int i; | |||
| spi_init(0,0); | |||
| wait_busy(); | |||
| spi_cs_on(SPI_CS_PIO_BASE, SPI_CS_FLASH); | ||
| spi_write(MDID); | ||
| notused = spi_read(); | ||
| write_address(0); |
| notused = spi_read(); | ||
| write_address(0); | ||
| #else | ||
| notused = spi_read(); |
| spi_write(RST); | ||
| notused = spi_read(); | ||
| spi_cs_off(SPI_CS_PIO_BASE, SPI_CS_FLASH); | ||
| for (i = 0; i < 18000; i++); |
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Okay to test. Company contributor agreement on file. |
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Our ext flash has a rather peculiar 'feature' in that we sometimes get an invalid response when first accessing the ext flash. Resetting the flash chip prior alleviates this problem.
This is highly specific and I don't expect this to make it into wolfboot as is, but I'm hopeful we can come to some sort of solution where we don't need to patch every new wolfboot version.
I'm also curious what function this particular line has: 3444c47#diff-315ae084c53140288a75552950c9b0dab78db6e39b69173980741b4687a7633bL181
To be honest, we don't actually know the whole reason for this bit any more. The original author is no longer working with us.