Hi Arnd,
On 10/15/13 2:01 PM, Arnd Bergmann wrote:
On Tuesday 15 October 2013, Dinh Nguyen wrote:
Hi Arnd,
On 10/15/13 7:50 AM, Arnd Bergmann wrote:
On Monday 14 October 2013, dinguyen@xxxxxxxxxx wrote:
+void socfpga_sysmgr_set_dwmmc_drvsel_smpsel(u32 drvsel, u32 smplsel)
+{
+ u32 hs_timing;
+
+ hs_timing = SYSMGR_SDMMC_CTRL_SET(smplsel, drvsel);
+ writel(hs_timing, sys_manager_base_addr + SYSMGR_SDMMCGRP_CTRL_OFFSET);
+}
+EXPORT_SYMBOL(socfpga_sysmgr_set_dwmmc_drvsel_smpsel);
This looks like the wrong approach. What are you trying to do? If you want to
set a clock, please use the clk API.
I can't use the clk API because this function is setting up a clock
phase bit for the SD/MMC
clock that is used to clock the card, not the IP. This register is
located outside the SD/MMC
and the clock manager.
Just to refresh your memory on this topic:
I tried to use the syscon approach that you suggested:
http://lists.infradead.org/pipermail/linux-arm-kernel/2013-May/168470.html
http://lists.infradead.org/pipermail/linux-arm-kernel/2013-May/170423.html
Ah, thanks. I knew this problem had come up before, I just didn't remember
it was for socfpga.
But this approach was rejected by Stephen Warren because we wanted to
the SD driver to be automonous
of registers outside its IP:
http://lists.infradead.org/pipermail/linux-arm-kernel/2013-August/194014.html
So I went with the approach of exposing a platform API so that the
SD/MMC platform specific
code can call it.
The system manager has a plethora of registers that controls other IPs
on the SOC, so I kinda thought
syscon was the way to go with this. A driver for this IP did not make
sense to me.
Please advise if you know of another approach?
I don't remember the details of what we have gone through before, but
I think this should still work:
1 Create a "syscon" backend driver to control your "system manager", which
lets other drivers hook into it without calling a private API.
Yes, if you look at drivers/mmc/host/dw_mmc-socfpga.c that is in the
mainline,
it is hooking into the "system manager" through "syscon". Is this what you
mean here?
The problem is because of the SYSMGR_SDMMCGRP_CTRL_OFFSET define
in this file. This means the SD/MMC driver needs information that is
outside of its IP.
Dinh
2 Create a trivial clock driver that is independent of your existing
clock driver and independent of the other drivers using the system
manager, by using syscon as the low-level interface.
3 Make the sdmmc driver use the normal clock API and link its clock to the
driver from step 2 in the device tree.
Is this what you have tried before?
Arnd
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