linux-kernel - Re: [PATCH 0/2] mmc: mmci: add quirk property to add stm32 transfer mode

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Date:   Wed, 27 Feb 2019 10:11:17 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Ludovic BARRE <ludovic.barre@...com>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        DTML <devicetree@...r.kernel.org>,
        Alexandre Torgue <alexandre.torgue@...com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        linux-stm32@...md-mailman.stormreply.com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 0/2] mmc: mmci: add quirk property to add stm32 transfer mode

On Mon, 25 Feb 2019 at 11:49, Ludovic BARRE <ludovic.barre@...com> wrote:
>
> hi Russell & Ulf
>
> On 2/21/19 3:03 PM, Russell King - ARM Linux admin wrote:
> > On Thu, Feb 21, 2019 at 02:38:36PM +0100, Ludovic BARRE wrote:
> >> hi Russell & Ulf
> >>
> >> On 2/21/19 11:30 AM, Russell King - ARM Linux admin wrote:
> >>> On Thu, Feb 21, 2019 at 10:27:39AM +0000, Russell King - ARM Linux admin wrote:
> >>>> On Thu, Feb 21, 2019 at 11:10:49AM +0100, Ludovic Barre wrote:
> >>>>> From: Ludovic Barre <ludovic.barre@...com>
> >>>>>
> >>>>> This patch series introduces a bitmap of hardware quirks that require
> >>>>> some special action. This should reduce the number of boolean
> >>>>> into variant structure.
> >>>>> And adds quirk bit to define sdmmc specific transfer modes.
> >>>>
> >>>> Please find some other way to deal with these differences.  As far as
> >>>> I'm concerned, introducing a quirk bitmask such as what was done in
> >>>> sdhci is a complete disaster and leads to long-term maintanability
> >>>> problems.
> >>>>
> >>>> We already have a way to deal with variants in mmci.
> >>>
> >>> ... to finish what I was saying ...
> >>>
> >>> and I think that:
> >>>
> >>>           if (variant->blksz_datactrl16)
> >>>                   datactrl = variant->datactrl_dpsm_enable | (data->blksz << 16);
> >>>           else if (variant->blksz_datactrl4)
> >>>                   datactrl = variant->datactrl_dpsm_enable | (data->blksz << 4);
> >>>           else
> >>>                   datactrl = variant->datactrl_dpsm_enable | blksz_bits << 4;
> >>>
> >>> ought to become a variant function call which returns the appropriate
> >>> datactrl value.  This would shrink the amount of variant testing in this
> >>> path, and also means that going forward we aren't facing an endlessly
> >>> increasing number of tests here.
> >>
> >> For blksz_datactrl case:
> >> We could create an inline function for datactrl16 and blksz_datactrl4
> >> which returns the appropriate datactrl value (specific for ux500v2 and
> >> qcom). This function could be register in mmci_host_ops structure.
> >
> > Yes, this is what I'm proposing (except for the "inline" bit which
> > seems meaningless if it's called via the mmci_host_ops structure.)
> > I'm also proposing that it shouldn't just be the blksz that's
> > returned but anything that the variant needs to take account of,
> > including the stm transfer mode.
>
> Ulf, are you alright with this callback approach (just to be sure that
> every body is align, before send a patch)?

Go ahead, let's see how it looks!

>
> This mmci_host_ops callback could return datactrl config to
> start data (defined by variant).

Yes.

[...]

Kind regards
Uffe