[PATCH v5] atmel_flexcom: Support backup mode

On 23/10/2017 at 19:03, Romain Izard wrote:

2017-10-23 18:07 GMT+02:00 Lee Jones [off-list ref]:

quoted

On Mon, 23 Oct 2017, Lee Jones wrote:

quoted

On Thu, 19 Oct 2017, Romain Izard wrote:

quoted

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 <redacted>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Tested-by: Nicolas Ferre <nicolas.ferre@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 <redacted>

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.

aka: Ultra Low Power modes (ULP0 and ULP1).

But if you think that it is necessary, I can reword the commit.

Thanks for the whole explanation Romain.

Yes we have such a wording in our documents and we used some kind of
"Backup mode", "Backup+Self-Refresh (B+SR or B+S-R)", "Backup and DDR in
Self-refresh" or "suspend-to-mem" wording for our patches. I take
advantage of this discussion to list all them here, for the record ;-)

So, I have the feeling that together with the commit message itself, we
can go with this wording.

Best regards,
-- 
Nicolas Ferre