linux-kernel - Re: [RFC PATCH 2/3] mmc: host: omap

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Date:	Mon, 23 May 2016 11:52:01 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Felipe Balbi <balbi@...nel.org>, Tony Lindgren <tony@...mide.com>,
	Peter Ujfalusi <peter.ujfalusi@...com>
CC:	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-mmc@...r.kernel.org>, <afenkart@...il.com>,
	<ulf.hansson@...aro.org>, <linux@...linux.org.uk>, <rogerq@...com>,
	<bcousson@...libre.com>, <galak@...eaurora.org>,
	<ijc+devicetree@...lion.org.uk>, <mark.rutland@....com>,
	<pawel.moll@....com>, <robh+dt@...nel.org>, <nsekhar@...com>
Subject: Re: [RFC PATCH 2/3] mmc: host: omap_hsmmc: Enable ADMA2

Hi Felipe,

On Friday 20 May 2016 12:06 AM, Felipe Balbi wrote:
> 
> Hi,
> 
> Tony Lindgren <tony@...mide.com> writes:
>> * Peter Ujfalusi <peter.ujfalusi@...com> [160519 01:10]:
>>> On 05/18/2016 10:30 PM, Tony Lindgren wrote:
>>>> Ideally the adma support would be a separate loadable module,
>>>> similar how the cppi41dma is a child of the OTG controller.
>>>
>>> The Master DMA is part of the hsmmc IP block. If the same ADMA module is
>>> present on other IPs it might be beneficial to have a helper library to handle
>>> it (allocating the descriptor pool, wrinting, updating descriptors, etc).
>>
>> OK. Yeah if it's part of the MMC controller it makes no sense to
>> separate it. So then the conecrns are using alternate DMA
>> implementations and keeping PM runtime working :)
>>
>> BTW, Felipe mentioned that the best thing to do in the long run would
>> be to set up sdhci-omap.c operating in ADMA mode.
>>
>> Felipe, care to summarize what you had in mind?
> 
> yeah, just write a new sdhci-omap.c to start moving away from
> omap-hsmmc.c, just like it was done for 8250-omap.
> 
> At the beginning, it could be just the bare minimum to get it working
> and slowly move over stuff like pm runtime, dmaengine, PIO. Move more
> platforms over to that driver and, eventually, get rid of omap-hsmmc.c
> altogether.
> 
> That way, development can be focussed on generic layers (SDHCI) to which
> OMAP MMC controller is compliant (apart from the VERSION register
> quirk).

About an year back, when I tried using SDHCI for OMAP I ran into issues and was
not able to get it working. IIRC SDHCI_PRESENT_STATE (or OMAP_HSMMC_PSTATE) was
not showing the correct state for card present and is unable to raise an
interrupt when a card is inserted. I didn't debug this further.

It also kept me wondering why gpio interrupt was always used for card detect
instead of using mmci_sdcd line of the controller.

Thanks
Kishon