Re: fsl-espi, m25p80 and max_transfer_size / max_message_size

[Heiner Kallweit <hkallweit1@xxxxxxxxx>]

Am 14.11.2016 um 15:22 schrieb Michael Walle:
> Hi,
> 
> since commit 02a595d5d6e4 (spi: fsl-espi: eliminate spi nor flash read loop) the fsl-espi is (partly?) broken. Reading 64k from the flash results in the following error:
>   fsl_espi ffe110000.spi: message too long, size is 65540 bytes
>   spi_master spi32766: failed to transfer one message from queue
> 
> We are using the m25p80 driver which checks the max_transfer_size. The fsl-espi driver sets the max_message_size to 64k. As far as I understand it, a message can contain multiple transfers. The m25p80 uses two transfers (one 4 byte and one with max_transfer_size, that is 64k) and thus the message has a total length of 65540 bytes which is too long for the driver.
> 
> I didn't find where the max_message_size is checked and I also don't know which part is resposible to handle the correct sizes. The m25p80 driver? Should it use spi_max_message_size() instead of spi_max_transfer_size() ?
> 
Your mail actually doesn't come as a surprise. The patch addressing this scenario is waiting to be applied.
See here: https://www.spinics.net/lists/linux-spi/msg08844.html

Rgds, Heiner

> For example:
> --- a/drivers/mtd/devices/m25p80.c
> +++ b/drivers/mtd/devices/m25p80.c
> @@ -172,7 +172,7 @@ static ssize_t m25p80_read(struct spi_nor *nor, loff_t from, size_t len,
> 
>         t[1].rx_buf = buf;
>         t[1].rx_nbits = m25p80_rx_nbits(nor);
> -       t[1].len = min(len, spi_max_transfer_size(spi) - t[0].len);
> +       t[1].len = min(len, spi_max_message_size(spi) - t[0].len);
>         spi_message_add_tail(&t[1], &m);
> 
>         ret = spi_sync(spi, &m);
> 
> -michael
> 

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