[OpenWrt-Devel] [PATCH 2/3] ipq40xx: mtd m25p80: fix hang on device shutdown

[Piotr Dymacz]

Hi Daniel,

On 30.10.2019 12:27, Daniel Danzberger wrote:
> Signed-off-by: Daniel Danzberger <daniel at dd-wrt.com>
> ---
>   .../401-mtd-m25p80-fix-shutdown-hang.patch    | 21 +++++++++++++++++++
>   1 file changed, 21 insertions(+)
>   create mode 100644 target/linux/ipq40xx/patches-4.19/401-mtd-m25p80-fix-shutdown-hang.patch
> 
> diff --git a/target/linux/ipq40xx/patches-4.19/401-mtd-m25p80-fix-shutdown-hang.patch b/target/linux/ipq40xx/patches-4.19/401-mtd-m25p80-fix-shutdown-hang.patch
> new file mode 100644
> index 0000000000..779f7ec4af
> --- /dev/null
> +++ b/target/linux/ipq40xx/patches-4.19/401-mtd-m25p80-fix-shutdown-hang.patch
> @@ -0,0 +1,21 @@
> +diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
> +index 270d3c95..39f90436 100644
> +--- a/drivers/mtd/devices/m25p80.c
> ++++ b/drivers/mtd/devices/m25p80.c
> +@@ -256,9 +256,16 @@ static int m25p_remove(struct spi_mem *spimem)
> + static void m25p_shutdown(struct spi_mem *spimem)
> + {
> + 	struct m25p *flash = spi_mem_get_drvdata(spimem);
> ++	u8 command[1];
> ++
> ++	command[0] = 0x66;
> ++	spi_write(spimem->spi, command, 1);
> ++	command[0] = 0x99;
> ++	spi_write(spimem->spi, command, 1);

This is not the correct way to solve 'broken' hardware designs (I assume 
your board has incorrect bootstrap configuration and boots from 32M SPI 
NOR in default 3-byte addressing mode instead of 4-byte or the flash IC 
isn't reset during SOC reset).

I remember discussing this topic at least several times during reviews 
of some MediaTek based boards back in 2018, please see great explanation 
from Mathias here: [0].

Since kernel 4.19 we have an official 'solution' for that, look for 
'broken-flash-reset' property description in [1] documentation and 
deeper explanation in [2].

[0] https://github.com/lede-project/source/pull/620#issuecomment-295401936

[1] 
https://www.kernel.org/doc/Documentation/devicetree/bindings/mtd/jedec%2Cspi-nor.txt

[2] 
https://github.com/torvalds/linux/commit/bb276262e88dae52cc717bb636b7468f66bb234e

-- 
Cheers,
Piotr

> +
> + 	spi_nor_restore(&flash->spi_nor);
> + }
> ++
> + /*
> +  * Do NOT add to this array without reading the following:
> +  *
> 


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