Re: [PATCH] ARM: davinci: da850: Fix pwm name matching

[David Lechner]

On 10/31/2016 05:18 AM, Sekhar Nori wrote:
On Tuesday 25 October 2016 11:24 PM, David Lechner wrote:
This fixes pwm name matching for DA850 familiy devices. When using device
tree, the da850_auxdata_lookup[] table caused pwm devices to have the exact
same name, which caused errors when trying to register the devices.
The names for clock matching in da850_clks[] also have to be updated to
to exactly match in order for the clock lookup to work correctly.

Signed-off-by: David Lechner <da...@lechnology.com>
---

Tested working on LEGO MINDSTORMS EV3.


 arch/arm/mach-davinci/da850.c    | 10 +++++++---
 arch/arm/mach-davinci/da8xx-dt.c | 10 +++++-----
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/arm/mach-davinci/da850.c b/arch/arm/mach-davinci/da850.c
index ed3d0e9..6b78a8f 100644
--- a/arch/arm/mach-davinci/da850.c
+++ b/arch/arm/mach-davinci/da850.c
@@ -510,9 +510,13 @@ static struct clk_lookup da850_clks[] = {
        CLK("vpif",           NULL,           &vpif_clk),
        CLK("ahci_da850",             NULL,           &sata_clk),
        CLK("davinci-rproc.0",        NULL,           &dsp_clk),
-       CLK("ehrpwm",         "fck",                &ehrpwm_clk),
-       CLK("ehrpwm",         "tbclk",      &ehrpwm_tbclk),
-       CLK("ecap",           "fck",                &ecap_clk),
+       CLK("ehrpwm.0",               "fck",                &ehrpwm_clk),
+       CLK("ehrpwm.0",               "tbclk",      &ehrpwm_tbclk),
+       CLK("ehrpwm.1",               "fck",                &ehrpwm_clk),
+       CLK("ehrpwm.1",               "tbclk",      &ehrpwm_tbclk),
+       CLK("ecap.0",         "fck",                &ecap_clk),
+       CLK("ecap.1",         "fck",                &ecap_clk),
+       CLK("ecap.2",         "fck",                &ecap_clk),

This has exposed a limitation of DaVinci clock framework. The struct clk
are stored as a linked list themselves. So a node repeating in the table
above will create a loop in the linked list. This is easily seen on the
LCDK board. davinci_clk_disable_unused() never returns. PWMs are unused
on that board.

There is no "simple" solution to this AFAICS. One solution is to
separate the iterator from the clock hardware structure and use struct
clk_hw available in struct clk_lookup.

Or move DaVinci to common clock framework. This is of course preferred
but much more involved as all 6 supported SoCs have to be moved together.

Thanks,
Sekhar



The simple solution for now could be to make child clocks for each of 
these that simply enable the parent clock. e.g. ehrpwm0_clk and 
ehpwm1_clk are children of ehrpwm_clk, etc.

Looking at da830.c, it looks like the solution was to make multiple 
clocks that use the same LPSC, but this does not seem right to me.