linux-kernel - Re: [PATCH] spmi-pmic-arb: support configurable number of peripherals

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Message-ID: <561EDAAC.6060800@codeaurora.org>
Date:	Wed, 14 Oct 2015 15:43:56 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	"Ivan T. Ivanov" <iivanov@...sol.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Gilad Avidov <gavidov@...eaurora.org>,
	Sagar Dharia <sdharia@...eaurora.org>
Subject: Re: [PATCH] spmi-pmic-arb: support configurable number of peripherals

On 09/15/2015 11:27 AM, Stephen Boyd wrote:
> On 09/15, Ivan T. Ivanov wrote:
>> On Mon, 2015-09-14 at 18:28 -0700, Stephen Boyd wrote:
>>> On 09/14/2015 02:54 PM, Stephen Boyd wrote:
>>>> The current driver implementation supports only 128 peripherals.
>>>> Add support for more than 128 peripherals by taking a lazy
>>>> caching approach to the mapping tables. Instead of reading the
>>>> tables at boot given some fixed size, read them on an as needed
>>>> basis and cache the results. We still assume a max number of 512
>>>> peripherals, trading off some space for simplicity.
>>>>
>>>> Based on a patch by Gilad Avidov <gavidov@...eaurora.org> and
>>>> Sagar Dharia <sdharia@...eaurora.org>.
>>>>
>>>> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
>>>> ---
>>> Hi Ivan,
>>>
>>> This patch causes 8916 to crash, because there isn't a mapping for ppid
>>> 257 in the ppid to channel table. It seems that we're reading the revid
>>> from the slave id 1 pmic by going through channel 0, which seems to be
>>> setup for ppid 9 (slave id 0 and the peripheral starting at 0x900). Can
>>> we stop reading the revid registers from non-zero slave id pmic devices?
>>> That would be one solution to fix this problem. Or maybe we need to
>>> special case this in the pmic arbiter code to fold ppid 0xN01 (slave id
>>> N and address 0x100) onto channel 0 all the time?
>>>
>> Yes, we can. We are not using this information at the moment.
>> Right now, revision read is more or less for debug purposes.
>>
>> Would following patch work for you? Of course it will be difficult
> Yes the patch works fine. Feel free to add a
>
> Tested-by: Stephen Boyd <sboyd@...eaurora.org>
>
>

I have to take this back. I missed the part where some pmics are on
slave id 2 or slave id 4, so this check isn't going to work. I've
adjusted it to use sid % 2 instead and I'll resend these two patches,
but I imagine to be more robust we're going to need to add a revid node
to the DT under the SID that actually has it. Then we can search the
child nodes for a revid compatible node and do the rev probing stuff.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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