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Date:   Thu, 21 Feb 2019 14:03:00 +0000
From:   Russell King - ARM Linux admin <linux@armlinux.org.uk>
To:     Ludovic BARRE <ludovic.barre@st.com>
Cc:     devicetree@vger.kernel.org, Ulf Hansson <ulf.hansson@linaro.org>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org,
        Rob Herring <robh+dt@kernel.org>,
        srinivas.kandagatla@linaro.org,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 0/2] mmc: mmci: add quirk property to add stm32 transfer
 mode
Message-ID: <20190221140300.y3tunrvsh3gyig5f@shell.armlinux.org.uk>
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 <20190221103049.tspc5igoe6wmt3jd@shell.armlinux.org.uk>
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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@st.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.

> in mmci_start_data function we could call a common function which call a
> hook if defined.
> 
> int mmci_dblksz(struct mmci_host *host)

As this is returning a register value, "u32" would be more appropriate
than "int".

> {
> 	if (host->ops && host->ops->dblksz)
> 		return host->ops->dblk(host);
> 
> 	/* default data block size definition */
> 	blksz_bits = ffs(data->blksz) - 1;
> 	return blksz_bits << 4;
> }
> 
> what do you think about it?

I don't see any reason not to make the call unconditional and have every
variant supply an appropriate function pointer.  IMHO that keeps stuff
cleaner.

> After, I'm afraid to multiply callback function in mmci_host_ops.
> 
> For stm32 transfer mode:
> ditto, a callback function or I keep a boolean?
> 
> BR
> Ludo
> 
> > 
> > > 
> > > > 
> > > > Ludovic Barre (2):
> > > >    mmc: mmci: introduce a quirks property into variant struct
> > > >    mmc: mmci: add quirk property to add stm32 transfer mode
> > > > 
> > > >   drivers/mmc/host/mmci.c | 11 +++++++++++
> > > >   drivers/mmc/host/mmci.h |  9 +++++++++
> > > >   2 files changed, 20 insertions(+)
> > > > 
> > > > -- 
> > > > 2.7.4
> > > > 
> > > > 
> > > > _______________________________________________
> > > > linux-arm-kernel mailing list
> > > > linux-arm-kernel@lists.infradead.org
> > > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> > > > 
> > > 
> > > -- 
> > > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> > > FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
> > > According to speedtest.net: 11.9Mbps down 500kbps up
> > > 
> > > _______________________________________________
> > > linux-arm-kernel mailing list
> > > linux-arm-kernel@lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> > > 
> > 
> 

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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