[U-Boot] [PATCH 6/7] mx35: Fix eSDHC clocks

[Benoît Thébaudeau]

Hi Stefano,

> >>> Even if the two controllers can have different clocks, this is
> >>> not
> >>> supported by the driver. In fact, in drivers/mmc/fsl_esdhc.c:
> >>>
> >>> int sdhc_clk = gd->sdhc_clk;
> >>>
> >>> The driver uses always the same clock, stored in the global
> >>> structure.
> >>> Before extending the code as in this patch, the driver should be
> >>> modified to handle separate clocks. Currently the driver supports
> >>> multiple controller, but they share the same clock or at least
> >>> the
> >>> same
> >>> frequency.
> >>
> >> Indeed, I had seen that. I didn't know what to decide as to the
> >> driver clocks,
> >> so I made this change to select the correct clock if a single
> >> clock
> >> or frequency
> >> is used.
> >>
> >> If several clock frequencies are to be supported at once, what
> >> kind
> >> of API would
> >> you like? gd->sdhc_clk could be changed to an array, then the
> >> corresponding
> >> index could be passed to the init function through the
> >> fsl_esdhc_cfg
> >> struct.
> > 
> > But there is also the issue of fsl_esdhc_mmc_init() that would need
> > a new config
> > just to pass this index. I don't like that. Any suggestion?
> 
> There is another issue. The driver is used by both ARM (i.MX) and
> PowerPCs (PowerQuickIII, ...).
> 
> fsl_esdhc_mmc_init() is already the interface when one parameter is
> enough. If we need more than one controller, we should already call
> fsl_esdhc_initialize() with the cfg structure.
> 
> Then adding a field to the struct fsl_esdhc_cfg is maybe not too bad.
> Instead of an index, we can add directly the frequency - reading the
> driver this is all that the driver needs.

OK, then this patch does the job for the single eSDHC instance use case, which
will still use gd->sdhc_clk. I will make another patch before or after this one
for the multi-instance use case. I will do the same in the v2 of my mx5 clock
series (for gd->sdhc_clk). I think I also have the same stuff for mx25.

Best regards,
Benoît