On Mon, 23 Oct 2017, Romain Izard wrote:
> 2017-10-23 18:07 GMT+02:00 Lee Jones <lee.jo...@linaro.org>:
> > On Mon, 23 Oct 2017, Lee Jones wrote:
> >> On Thu, 19 Oct 2017, Romain Izard wrote:
> >>
> >> > The controller used by a flexcom module is configured at boot, and left
> >> > alone after this. As the configuration will be lost after backup mode,
> >> > restore the state of the flexcom driver on resume.
> >> >
> >> > Signed-off-by: Romain Izard <romain.izard....@gmail.com>
> >> > Acked-by: Nicolas Ferre <nicolas.fe...@microchip.com>
> >> > Tested-by: Nicolas Ferre <nicolas.fe...@microchip.com>
> >> > ---
> >> > Changes in v5:
> >> > * extract from the patch series, and send as a standalone patch
> >> >
> >> > drivers/mfd/atmel-flexcom.c | 65
> >> > ++++++++++++++++++++++++++++++++++-----------
> >> > 1 file changed, 50 insertions(+), 15 deletions(-)
> >> >
> >> > diff --git a/drivers/mfd/atmel-flexcom.c b/drivers/mfd/atmel-flexcom.c
> >> > index 064bde9cff5a..ef1235c4a179 100644
> >> > --- a/drivers/mfd/atmel-flexcom.c
> >> > +++ b/drivers/mfd/atmel-flexcom.c
> >> > @@ -39,34 +39,44 @@
> >> > #define FLEX_MR_OPMODE(opmode) (((opmode) << FLEX_MR_OPMODE_OFFSET)
> >> > & \
> >> > FLEX_MR_OPMODE_MASK)
> >> >
> >> > +struct atmel_flexcom {
> >> > + void __iomem *base;
> >> > + u32 opmode;
> >> > + struct clk *clk;
> >> > +};
> >> >
> >> > static int atmel_flexcom_probe(struct platform_device *pdev)
> >> > {
> >> > struct device_node *np = pdev->dev.of_node;
> >> > - struct clk *clk;
> >> > struct resource *res;
> >> > - void __iomem *base;
> >> > - u32 opmode;
> >> > + struct atmel_flexcom *afc;
> >>
> >> Nit: I'd prefer if you call this 'ddata'.
> >>
> >> But the concept and implementation is fine, so if you're going to
> >> change it please do so and apply my:
> >>
> >> Acked-by: Lee Jones <lee.jo...@linaro.org>
> >
> > Also, 'back-up mode' isn't really a thing is it?
> >
> > How about "Reinstall state on resume" or similar?
> >
>
> The expression comes from the SAMA5D2's datasheet.
>
> Other Atmel chips use a different single suspend mode with Linux, where
> the SoC remains completely powered with a slow clock. The registers are
> preserved in this mode, so there is no need for a specific suspend and
> resume code.
>
> The SoC can also be powered down, but the CPU is reset and only a small
> part is powered with a backup battery to maintain a valid RTC and a
> small internal SRAM.
>
> In the SAMA5D2, the mode with only the backup power supply has been
> extended to isolate the memory I/O lines, making it possible to keep the
> external SDRAM memory in self-refresh. This mode has a lower consumption
> compared to the slow clock mode, but it has a higher wakeup latency, and
> needs specific software support in the bootloader and the kernel.
>
> As a result, the "backup mode" expression is used to contrast with the
> "slow clock" expression when describing the different suspend modes
> supported by the chip.
>
> But if you think that it is necessary, I can reword the commit.
No, no need. Thanks for the excellent explanation.
It might be worth you providing a succinct description of the
datasheet's meaning of "back-up mode" though.
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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