Re: [PATCH/RFC] ARM: shmobile: r8a7794: Add Audio DMAC, PWM and Thermal clocks to device tree

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Geert,

On Monday 05 January 2015 09:52:37 Geert Uytterhoeven wrote:
> On Mon, Jan 5, 2015 at 9:30 AM, Laurent Pinchart wrote:
> > On Friday 19 December 2014 09:39:33 Simon Horman wrote:
> >> This is based on the MSTP5 clocks in the r8a7791 device tree.
> >> The main difference being that the r8a7794 does not have an Audio DMAC1
> >> clock.
> >> 
> >> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
> >> 
> >> ---
> >> Based on the renesas-devel-20141217-v3.18 tag of my renesas tree.
> >> 
> >> N.B: The R-Car Gen2 v1.8.0 BSP uses zs_clk whereas this patch uses hp_clk
> >>      as the parent clock for the Audio DMAC clock.
> >>      
> >>      In that regard this patch follows the pattern used in mainline for
> >>      the r8a7790 and r8a7791 SoCs.
> >>      
> >>      The BSP's parent clock is consistent for the r8a7790, r8a7791,
> >>      r8a7793 and r8a7794 SoCs.
> > 
> > Does this mean the BSP uses hp_clk for all Gen2 SoCs while mainline uses
> > zs_clk ?
> 
> No, it's the other way around ;-)

Sorry, that's what I meant.

> > Can't we find out which one is correct ?
> 
> Which clock is used doesn't seem to be documented.
> So either we have to check with the hardware guys, or measure the clock
> in some way, either by hardware or software (e.g. what's the maximum
> transfer rate that works?).

Given the parent clock frequencies (130 MHz and 260 MHz) and the audio rates, 
I'm not sure any useful measurement could be performed.

-- 
Regards,

Laurent Pinchart