linux-kernel - Re: [PATCH] drm/omap: Migrate minimum FCK/PCK ratio from Kconfig to dts

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Message-ID: <f01bf6ec-e531-371b-4f66-312b12379273@ti.com>
Date:   Tue, 1 Oct 2019 12:31:38 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Tero Kristo <t-kristo@...com>, Adam Ford <aford173@...il.com>
CC:     "H. Nikolaus Schaller" <hns@...delico.com>,
        Tony Lindgren <tony@...mide.com>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        Adam Ford <adam.ford@...icpd.com>,
        Benoît Cousson <bcousson@...libre.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/omap: Migrate minimum FCK/PCK ratio from Kconfig to
 dts

On 01/10/2019 11:12, Tero Kristo wrote:
> On 01/10/2019 08:07, Tomi Valkeinen wrote:
>> On 30/09/2019 20:48, Tero Kristo wrote:
>>
>>> Hmmh, after some testing, it seems there is bad stuff happening with 
>>> the divider clock implementation, I am re-working it as of now. 
>>> Basically what is wrong is that with a divider max value of say 16, 
>>> the driver attempts to craft the max value into a mask, but this ends 
>>> up being 0x1f. If the max value is 15, it ends up into 0xf which is 
>>> correct.
>>
>> Ok, that explains the max not working.
>>
>> It doesn't explain the other issue, where the TRM says the max div is 
>> 32, but it does not work. But taking the max div from the old SoCs, 
>> 16, is not correct either, as it seems that dividers up to 31 work ok.
>>
>>   Tomi
>>
> 
> Ok, attached a series that hopefully fixes it, any testing feedback 
> welcome before I post this properly.
> 
> This also supports omap36xx dpll4_m4_ck divider up-to 31, other omap3 
> family is limited to 16.

Works for me. This also needs the change to dss.c to change the max from 
32 to 31. I'll send a patch for that separately.

  Tomi

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