[U-Boot] [PATCH 1/2] mxc_ocotp: Do not disable the OCOTP clock after every access

[Benoît Thébaudeau]

Hi Fabio,

On Tue, Nov 25, 2014 at 4:11 PM, Fabio Estevam
<fabio.estevam at freescale.com> wrote:
> Leave the OCOTP turned on, so that we subsequent access do not fail.
>
> After enabling the thermal driver on a mx6sxsabresd board:
>
> U-Boot 2015.01-rc1-18267-g99d4189-dirty (Nov 24 2014 - 12:59:01)
>
> CPU:   Freescale i.MX6SX rev1.0 at 792 MHz
> CPU:   Temperature 48 C
> Reset cause: POR
> Board: MX6SX SABRE SDB
> I2C:   ready
> DRAM:  1 GiB
> PMIC:  PFUZE100 ID=0x10
> MMC:   FSL_SDHC: 0, FSL_SDHC: 1, FSL_SDHC: 2
>   00:01.0     - 16c3:abcd - Bridge device
>    01:00.0    - 8086:08b1 - Network controller
> In:    serial
> Out:   serial
> Err:   serial
> Net:
> (hang)
>
> As the thermal driver accesses the ocotp registers, its clock will be disabled
> afterwards.
>
> Then when the MAC address is read (also from ocotp registers) it will cause a
> hang.
>
> Do not disable the ocotp clock to prevent this problem.
>
> Signed-off-by: Fabio Estevam <fabio.estevam at freescale.com>
> ---
>  drivers/misc/mxc_ocotp.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/drivers/misc/mxc_ocotp.c b/drivers/misc/mxc_ocotp.c
> index 3de1245..67f9429 100644
> --- a/drivers/misc/mxc_ocotp.c
> +++ b/drivers/misc/mxc_ocotp.c
> @@ -81,8 +81,6 @@ static int finish_access(struct ocotp_regs *regs, const char *caller)
>         err = !!(readl(&regs->ctrl) & BM_CTRL_ERROR);
>         clear_error(regs);
>
> -       enable_ocotp_clk(0);
> -
>         if (err) {
>                 printf("mxc_ocotp %s(): Access protect error\n", caller);
>                 return -EIO;

That, or:
 - Make imx_get_mac_from_fuse() call enable_ocotp_clk(1) before
reading the fuses, then call enable_ocotp_clk(0).
 - Make enable_ocotp_clk() return the clock initial state and store it
in prepare_access(), then restore it in finish_access(). Same in
imx_get_mac_from_fuse().

Which of these 3 choices do you think would be the best?

Regards,
Benoît