Re: [PATCH v2 0/3] Add the efuse driver on rockchip platform

[Caesar Wang]

å 2015å06æ18æ 16:29, Srinivas Kandagatla åé:
> On 18/06/15 08:05, Stefan Wahren wrote:
> > Hi Srinivas,
> >
> > Am 16.06.2015 um 12:54 schrieb Srinivas Kandagatla:
> > > On 16/06/15 11:06, Caesar Wang wrote:
> > > > Hi Srinivas,
> > > >
> > > > å 2015å06æ16æ 17:21, Srinivas Kandagatla åé:
> > > > > Hi Stefan,
> > > > >
> > > > >
> > > > > On 16/06/15 09:52, Stefan Wahren wrote:
> > > > > > Hi Caesar,
> > > > > >
> > > > > > [add Maxime and Srinivas]
> > > > > >
> > > > > > Am 16.06.2015 um 09:27 schrieb Caesar Wang:
> > > > > > > The original driver is uploaded by Jianqun.
> > > > > > > Here is his patchs:
> > > > > > >       https://patchwork.kernel.org/patch/5410341/
> > > > > > >       https://patchwork.kernel.org/patch/5410351/
> > > > > > >
> > > > > > > Jianqun, nevermind!
> > > > > > > I check-pick it and re-upload the driver for the upstream.
> > > > > > > e.g.:
> > > > > > >       Tested by on minnie board.(kernel-4.1-rc8)
> > > > > > >       cd /sys/devices/platform/ffb40000.efuse
> > > > > > >       localhost ffb40000.efuse # cat cpu_leakage_show
> > > > > > >       cpu_version_show
> > > > > > >       The results:
> > > > > > >               19
> > > > > > >               2
> > > > > > >
> > > > > > > Changes in v2:
> > > > > > > - Change the document decription.
> > > > > > > - Move the efuse driver into driver/soc/vendor.
> > > > > > > - update the efuse driver.
> > > > > > > - Add the dts node on RK3288.
> > > > > >
> > > > > > i want to mention that there is a upcoming new framework suitable 
> > > > > > for
> > > > > > efuse drivers:
> > > > > >
> > > > > > https://lkml.org/lkml/2015/5/21/643
> > > > > >
> > > > > > Unfortunately i don't know the current development state.
> > > > >
> > > > > Currently this framework is used by atleast 3 drivers(qcom-tsens,
> > > > > qcom-cpr, begel-bone-cape manager) which are still floating in the
> > > > > mailing list.
> > > > >
> > > > > I was hoping that these 3 users would getback with tested-by.. which
> > > > > did not happen for last 3-4 weeks.
> > > > >
> > > > > I would appreciate, If you could try framework too, and let me know.
> >
> > yes i work on OCOTP driver for MXS platform and i will try ...
> >
> > > int rockchip_efuse_reg_read(void *context, unsigned int reg, unsigned
> > > int *val)
> > > {
> > >      /* efuse specific read sequence */
> > >      ...
> > > }
> >
> > I will need a specific read sequence too.
>
> You can have a look at 
> https://git.linaro.org/people/srinivas.kandagatla/linux.git/blob/b4c3ad253747767511233687436f20144e850d67:/drivers/nvmem/rockchip-efuse.c
>
> I did modify the rockchip driver, which I guess should be very much 
> similar to what OCOTP driver would need.

That rockchip-efuse.c driver shouldn't be work.

An entire 8-bit word of data can be read in one read operation with 
STROBE being high and a proper address
selected (address signals A5~A7 are âdonât caresâ).

That's great if we can get the content from the .reg_read when the 
consumer driver
callback the nvmem_cell_read().

e.g.:
static struct regmap_config rockchip_efuse_regmap_config = {
    .reg_bits = 32,
    .val_bits = 8,
    .reg_stride = 1,
    .reg_read = rockchip_efuse_reg_read,
};
...
/ * consumer driver */
nvmem_cell_get()/nvmem_cell_put();
nvmem_cell_read()/nvmem_cell_write();
........


> > Sorry for these newbie questions:
> >
> > What data structure does context points to for this reg_read opteration?
> >
> > Do we need range checking of reg or is it handled by the framework?
> We already have that in place.
>
> > Are there any limitation for reg_read regarding sleeping or locking
> > operations?
> There are no limitaions as such from nvmem framework, regmap might 
> have limitations w.r.t to sleeping and fast_io, as fast_io would take 
> spinlocks, AFAIK the providers would not have fast_io, as they not IO 
> devices.
> > In case of a read only driver, is everything handle by devicetree or do
> > we need an empty write operation?
> Yes, if you pass read-only flag in the provider, the framework would 
> not attempt to even write.
>
> You will find answers to most of your question in the rochip-efuse.c 
> file.
>
>
> --srini
> > Best regards
> > Stefan

--
Thanks,
- Caesar


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