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[v2,0/3] hwmon: Add reset support to aspeed-pwm-tach

Message ID 20171102035349.1902-1-joel@jms.id.au
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Series hwmon: Add reset support to aspeed-pwm-tach | expand

Message

Joel Stanley Nov. 2, 2017, 3:53 a.m. UTC 
Gunter,

This adds reset controller support to the ASPEED pwm/tach driver. The reset
controller and clock driver is currently under review, so to test those patches
must be merged in to fully test these changes[1].

To address your concerns from v1:

This driver was not usable as-is upstream. I believe the developer(s) tested and
deployed it in the OpenBMC kernel tree which has some hacks in mach-aspeed to
release all of the resets. The other way they could have tested it is by
booting an OpenBMC kernel, which releases the resets, and then testing the
upstream kernel without performing a power cycle as the resets are not
reasserted on reboot.

I realise it is not ideal to be changing already merged bindings. I don't plan
on it becoming a habit.

There is no BIOS or other ROM that runs before Linux on a BMC to release
the resets. We do have u-boot, but that does not modify the pwm reset.

I haven't added a Kconfig dependency on the RESET_CONTROLLER as the driver can
build without it, and when the ASPEED clk/reset driver is merged, the platform
will always have that option selected.

I've given this version a day of testing on hardware I have access to.

[1] https://lwn.net/Articles/737697/

Joel Stanley (3):
  hwmon: (aspeed-pwm-tacho) Sort headers
  hwmon: (aspeed-pwm-tacho) Deassert reset in probe
  dt-bindings: hwmon: aspeed-pwm-tacho: Add reset node

 .../devicetree/bindings/hwmon/aspeed-pwm-tacho.txt | 14 ++++-------
 drivers/hwmon/aspeed-pwm-tacho.c                   | 27 +++++++++++++++++++---
 2 files changed, 29 insertions(+), 12 deletions(-)

-- 
2.14.1

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Comments

Rob Herring Nov. 6, 2017, 9:42 p.m. UTC | #1 
On Thu, Nov 02, 2017 at 02:53:49PM +1100, Joel Stanley wrote:
> The device tree bindings are updated to document the resets phandle, and

> the example is updated to match what is expected for both the reset and

> clock phandle.

> 

> Note that the bindings should have always had the reset controller, as

> the hardware is unusable without it.

> 

> Signed-off-by: Joel Stanley <joel@jms.id.au>

> ---

>  .../devicetree/bindings/hwmon/aspeed-pwm-tacho.txt         | 14 +++++---------

>  1 file changed, 5 insertions(+), 9 deletions(-)


Acked-by: Rob Herring <robh@kernel.org>


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