Hi,
On 20 November 2015 at 03:13, Valentin Longchamp valentin.longchamp@keymile.com wrote:
On 19/11/2015 17:57, Jagan Teki wrote:
On 13 November 2015 at 18:55, Valentin Longchamp valentin.longchamp@keymile.com wrote:
The release command is the pendant of the probe command. This command allows to call spi_flash_free from the command line. This may be necessary for some boards where sf probe does change the state of the hardware (like with some pin multiplexing changes for instance).
So you want to change the state of pin multiplexing on your board with connected slave devices example: spi nor flash is it? what exactly the need of releasing? why can't we use pin multiplexing changes like selecting or deselecting particular lines through driver or from board files itself.
That's our use case yes. Let me explain you it again in detail. Some of the signals used to access the NAND Flash and the SPI NOR are shared. At reset, they are available for the SPI NOR, since u-boot is in there and the CPU then accesses it.
In an usual boot sequence, the SPI NOR is accessed first (copying u-boot to the RAM, reading out the environment) and so the pins are configured in hardware at boot time for accessing the SPI NOR. After that, they are configured to access the NAND where the kernel and filesystem are stored to boot Linux thanks to env_relocate_spec() calling spi_flash_free() on exit in conjunction with [1]
Now in the case where the boot sequence is interrupted and some accesses are done to the SPI NOR, the pins are changed again to SPI NOR to perform these accesses. But we have to make sure that the pins are configured back to NAND by calling spi_flash_free() after these accesses and that's why I introduced the release() function.
In our case, there are 2 types of such accesses:
- environment variables write: this is the first patch of the series. It simply
adds calls to spi_flash_free() at function exit no only in env_relocate_spec() but also in saveenv() so that the behavior here is coherent for the whole env_sf file (spi_flash_probe() at function start, spi_flash_free() at function exit).
- updating u-boot: this is solved for us with the last 2 patches of the series.
The first one just adds a sf release command that does the opposite/cleanup to sf probe and the second patch just calls this command in our scripts where u-boot is updated/the SPI NOR is written.
We are *indeed* using pin multiplexing changes, in our case, they are implemented in the spi controller driver: drivers/spi/kirkwood_spi.c. To be very specific, in our case this sf release command allows to explicitely call spi_flash_free() which calls spi_free_slave(), which in our case (kirkwood_spi.c) sets the pins back to their previous configuration.
Does your board use driver model from SPI and SPI flash? If not I think that should be the first step.
Regards, Simon [snip]