Date: Wed, 10 Apr 2013 12:50:56 -0600 From: Ian Lepore <ian@FreeBSD.org> To: Adrian Chadd <adrian@FreeBSD.org> Cc: Aleksandr Rybalko <ray@FreeBSD.org>, Dmytro <dioptimizer@gmail.com>, freebsd-mips@FreeBSD.org Subject: Re: [PATCH] MMC/SD SPI-mode driver Message-ID: <1365619856.41399.242.camel@revolution.hippie.lan> In-Reply-To: <CAJ-Vmo=%2BtuHC4WA_5xPtjdJMGMn-_g6p5Nn7YjoPcuqb0s9AKg@mail.gmail.com> References: <CAK1zEjs=hC%2BpAYBgGq4t7%2BA_JPLaH6rhvEjD%2B1RNk1Ziu8E-4g@mail.gmail.com> <CAD44qMWpz-sjNKwRH6K=xicFXYutfk7R%2BN%2B%2Bo7cbgTg7rcQbkA@mail.gmail.com> <CAK1zEjuVZU4A59q5GxLcKTnFF9mcrbVmJ=w268uSJ=3sxVf1PA@mail.gmail.com> <CAD44qMURrssyXUz-%2Btd226chPA_MbKJ29ZApozbT2cEYbQwSqw@mail.gmail.com> <CAJ-Vmo=nQMuuJAW786egjuXCf0LGOd9g%2BCEEKdOJjPLRQFpKUg@mail.gmail.com> <20130407011307.9a9a9d64.ray@freebsd.org> <CAJ-Vmo=aeLCmBYpn9YMsGjq%2B9aF_Es-rByJ3RSnYkJYUECtLuQ@mail.gmail.com> <20130407022428.86a66c6a.ray@freebsd.org> <CAJ-VmokXseALmvvA9wsgZEBKSP0AGA988592TbsRb%2B4F0-UEcw@mail.gmail.com> <20130408153334.9cc11688aedbf32dcbf83a7b@freebsd.org> <CAJ-Vmo=irADrYgM1Aw=fHbnO%2Bgf7kHy_xHeSY9mzTSifo34frg@mail.gmail.com> <1365605147.41399.227.camel@revolution.hippie.lan> <CAJ-Vmon3v1CV08u7dqn1w=Jwih2eCfjtJdmB_OjZU3cSzx-baA@mail.gmail.com> <1365609642.41399.237.camel@revolution.hippie.lan> <CAJ-Vmo=%2BtuHC4WA_5xPtjdJMGMn-_g6p5Nn7YjoPcuqb0s9AKg@mail.gmail.com>
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On Wed, 2013-04-10 at 10:21 -0700, Adrian Chadd wrote:
> On 10 April 2013 09:00, Ian Lepore <ian@freebsd.org> wrote:
>
> > I don't understand how reading is not a generic spi command
> > (presupposing the existance of the proposed changes that allow for a spi
> > read without a concurrent write and vice versa).
>
> No. Reading is an SPI method. But the SPI flash command for reading
> data is different than other SPI commands.
>
> The only thing we should be doing this for is SPI _flash reads_. Not
> SPI reads. Just data area reads from a directly attached flash chip.
>
> It's dirty or inefficient any way we do this. Either we special case
> spibus drivers, or we expose a SPI read / SPI write 'command' that
> knows it's not a generic SPI bus transaction but specifically a
> read-this-flash-data-from-this-offset-and-length transaction. Or some
> other kind of dirty hack.
>
Maybe something like this could work?
static int
ar71xx_spi_transfer(device_t dev, device_t child, struct spi_command *cmd)
{
if (cmd->cs == sc->magic_mapped_flash_chipsel &&
cmd->tx_cmd == NULL && cmd->tx_data == NULL &&
*(uint8_t *)cmd->rx_cmd == SPIFLASH_READ_OPCODE &&
/* maybe some other constraints I don't know about */
/* maybe even check that child is the mx25l driver */)
return do_magic_mapped_read(...);
else
return do_mundane_nonmapped_transfer(...);
}
-- Ian
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