[PATCH] mtd: spi-nor: fsl-quadspi: add big-endian support
Han Xu
han.xu at freescale.com
Wed Nov 11 09:51:13 PST 2015
On Fri, Oct 30, 2015 at 04:49:41AM -0500, Yuan Yao-B46683 wrote:
> Hi Fabio Estevam,
>
> Thanks for your suggestion.
> We have an internal discussions for that.
>
> We think that:
> According to the initial commit message of regmap, it is targeting non-memory mapped buses. (regmap: Add generic non-memory mapped register access API) But in the imx2_wdt driver, it is used for memory-mapped register space. So it seems that using such a complex framework just to deal with endian is an over-kill.
>
> when it is not necessary to enable the clock every time we access the register.
> We don't think it is obvious to us how to use it for handling endianness, especially not the way imx2_wdt uses regmap. __regmap_init_mmio_clk() calls regmap_mmio_gen_context() which errors out if reg_format_endian is not REGMAP_ENDIAN_DEFAULT or REGMAP_ENDIAN_NATIVE, and elsewhere regmap-mmio.c It seems only little-endian accessors.
>
> Although it is possible to add the endianness support in the regmap_mmio driver, we don't see too much value in using it especially
>
> So we think:
> static void qspi_writel(struct fsl_qspi *q, u32 val, void __iomem
> *addr) {
> if (q->big_endian)
> iowrite32be(val, addr);
> else
> iowrite32(val, addr);
> }
> This way is an easier, more effective solution to do the endian issue.
>
> How about your think?
I think the implement is fine, but I prefer to use quirk rather than
read from dts? Please also rebase the patch to latest l2-mtd code.
>
> Best Regards,
> Yuan Yao
>
> On Sat, Oct 24, 2015 at 11:47 PM, Fabio Estevam <festevam at gmail.com> wrote:
> > On Fri, Oct 23, 2015 at 5:53 AM, Yuan Yao <yao.yuan at freescale.com> wrote:
> >
> > > +static void qspi_writel(struct fsl_qspi *q, u32 val, void __iomem
> > > +*addr) {
> > > + if (q->big_endian)
> > > + iowrite32be(val, addr);
> > > + else
> > > + iowrite32(val, addr);
> > > +}
> >
> > I suggest you to implement regmap support for this driver instead.
> >
> > Take a look at drivers/watchdog/imx2_wdt.c for a reference.
> >
> > Then you only need to pass 'big-endian' as a property for the qspi in the .dtsi
> > file and regmap core will take care of endianness.
--
Best Regards,
Han "Allen" Xu
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