Re: [PATCH v7 1/6] clk: shmobile: sh73a0 common clock framework implementation

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

Hi Magnus,

On Thursday 11 December 2014 19:07:27 Magnus Damm wrote:
> On Thu, Dec 11, 2014 at 3:39 AM, Laurent Pinchart wrote:
> > Hi Ulrich,
> > 
> > (CC'ing Morimoto-san)
> > 
> > On Wednesday 10 December 2014 17:53:22 Ulrich Hecht wrote:
> >> On Wed, Dec 10, 2014 at 4:38 PM, Laurent Pinchart wrote:
> >> > On Wednesday 10 December 2014 15:45:22 Ulrich Hecht wrote:
> >> >> Driver for the SH73A0's clocks that are too specific to be supported
> >> >> by a
> >> >> generic driver.
> >> 
> >> [...]
> >> 
> >> >> +static struct div4_clk div4_clks[] = {
> >> >> +     { "zg", "pll0", CPG_FRQCRA, 16 },
> >> > 
> >> > I've already commented on this in v6, the comment has probably been
> >> > overlooked. According to the datasheet the ZGFC value 1010 results in a
> >> > x1/5 factor, which  doesn't match the value in the div4_div_table
> >> > below.
> >> > I wonder if it could be an error in the datasheet though.
> >> 
> >> The legacy driver doesn't make an exception for zg.  Looks like an
> >> error in the datasheet to me.
> > 
> > Morimoto-san, do you think it would be possible to get that information
> > from the hardware team(s) ?
> > 
> > In the meantime I don't think this is a show stopper.
> 
> Let me step in here for a sec. I think getting reliable new information
> about sh73a0 is highly unlikely. That particular SoC is both old and part of
> the mobile line up that was chopped off quite some time ago. So I don't
> think anyone with knowledge is left in the company.

Fair enough, I was quite expecting that, but I possibly naively thought it 
would be worth trying :-)

It should in theory be possible to test this by measuring the SGX perfomances, 
but I don't think that would be feasible in practice in our team. I'm thus 
fine considering this as an error in the documentation until proven wrong. It 
should probably be captured in a comment in the source code though.

-- 
Regards,

Laurent Pinchart