Subject: Re: [m68k, powerpc, dma, ethernet, freescale RFA] Coldfire m54xx FEC ethernet driver

From: Greg Ungerer <[email-masked]>
Date: Wed, 24 Oct 2012 16:30:08 +1000

Hi Philippe,

On 16/10/12 18:03, Philippe De Muyter wrote:
> On Tue, Oct 16, 2012 at 04:39:05PM +1000, Greg Ungerer wrote:
>> On 09/10/12 19:07, Philippe De Muyter wrote:
>>> [CCing lkml, linux-ppc, netdev, linux-m68k]
>>>
>>> Hello kernel sources architects
>>>
>>> I have a working driver for the m54xx FEC ethernet driver that I
>>> would like to integrate in the kernel tree.  Problems are that
>>> - this driver needs an associated DMA driver (provided by FreeScale)
>>> wich is not dma-engine enabled
>>> - they're are already many fec drivers in the kernel tree, and
>>> at least one, fec_mpc52xx.c, seems to be very similar (information
>>> below), to the one for the mcf54xx, except it uses a differently
>>> named associated DMA driver (BestComm/SmartDma/SDMA) which is also
>>> not dma-engine enabled, and even kept hidden in /arch/powerpc where
>>> it is inaccessible when compiling for m68k.  The underlying DMA part
>>> from Freescale however seems similar to the one used in the
>>> m54xx. (again, see information below)
>>>
>>> So, now I am lost, what should I do ?
>>>
>>> The current state of my patches
>>> [http://mailman.uclinux.org/pipermail/uclinux-dev/2012-September/052147.html]
>>> is pushing the freescale provided MCD_DMA dma driver to /drivers/dma,
>>> without adding the dma-engine compatibility layer, and adding the specific
>>> fec_m54xx ethernet driver to /drivers/net/ethernet/freescale
>>
>> Do you get any responses?
>> I didn't see any...
>
> No, and none also about my simpler patch moving arch/powerpc/sysdev/bestcomm
> to drivers/dma/bestcomm (except a private and useful one telling me how to
> set '-M' option as default for 'git format-patch'), but at least this simpler
> patch seems to be in a wait bucket at
> http://patchwork.ozlabs.org/project/linuxppc-dev/list/.

Well, something useful then :-)

Feel free to send me the m68k header file updates as a patch (or patches
as appropriate), lets get those in now. They are worthwhile changes
on their own.

In light of no other other feedback you may want to push ahead then
with your patches to put the DMA engine code in drivers/dma. That
does seem like the right place to put it.

The new fec driver code should go to the netdev list for review.

Regards
Greg

> Regards
>
> Philippe
>
> PS: -M as default for 'git format-patch':
>
> put
> 	[diff]
> 		renames = true
> in .git/config
>
>>
>> Regards
>> Greg
>>
>>
>>
>>> On Tue, Oct 09, 2012 at 04:12:44PM +1000, Greg Ungerer wrote:
>>>> Hi Philippe,
>>>>
>>>> On 05/10/12 01:03, Philippe De Muyter wrote:
>>>>> On Thu, Oct 04, 2012 at 04:56:01PM +0200, Philippe De Muyter wrote:
>>>>>> On Thu, Oct 04, 2012 at 11:33:32PM +1000, Greg Ungerer wrote:
>>>>>>>
>>>>>>> My biggest concern is the amount of MCD/DMA support code. And it is
>>>>>>> all done quite differently to everything else in the kernel. We may
>>>>>>> get a bit of push back from kernel folk who look after DMA.
>>>>>>
>>>>>> Actually, there is already a similar code in
>>>>>> arch/powerpc/sysdev/bestcomm
>>>>>> (also from freescale, maybe an identical part, but I did not find any
>>>>>> usable doc), but the powerpc folks kept that hidden in the arch/powerpc
>>>>>> tree, instead of installing it in drivers/dma.
>>>>>
>>>>> The MCD DMA or DMA FEC code from freescale has a comment implying that
>>>>> this
>>>>> was first used in the MPC8220 part.  And Montavista has a MPC8220 port,
>>>>> but
>>>>> I did not find it, so I do not know where they installed the MCD DMA
>>>>> driver.
>>>>
>>>> Ok, looks like there is a bit a variance in all this.
>>>
>>> I also began to read the mpc5200 user's guide parts about the fec and
>>> BestComm/SmartDma/SDMA (not sure which one is the official FreeScale name)
>>> and they look very similar, but not identical, to their m54xx
>>> counterparts.
>>>
>>> It seems possible to make the fec_mpc52xx.c driver work for the m54xx
>>> but that needs at least:
>>> - moving some files or part of them from /arch/powerpc/sysdev and
>>>     /arch/powerpc/include/asm to /drivers/dma and /include/linux,
>>> - renaming the fec_mpc52xx files to a more sensible name,
>>> - providing out_be32 and in_be32 in /arch/m68k/include/asm/io.h,
>>> - and then unifying the interface to BestComm/SmartDma/SDMA and MCD_DMA
>>>     in mcf_52xx.c.
>>>
>>> An additional problem is that the freescale docs for powerpcs and for
>>> coldfires do not use the same mnemonics for the same registers.
>>>
>>> e.g. FEC registers
>>> 	offset	MPC5200		MCF5484
>>> 	======	=======		=======
>>> 	000	FEC_ID		n/a
>>> 	004	IEVENT		EIR
>>> 	008	IMASK		EIMR
>>> 	010	R_DES_ACTIVE	n/a
>>> 	014	X_DES_ACTIVE	n/a
>>> 	024	ECNTRL		ECR
>>> 	040	MII_DATA	MDATA
>>> 	044	MII_SPEED	MSCR
>>> 	064	MIB_CONTROL	MIBC
>>> 	084	R_CNTRL		RCR
>>> 	088	R_HASH		RHR
>>> 	0C4	X_CNTRL		TCR
>>> 	0E4	PADDR1		PALR
>>> 	0E8	PADDR2		PAHR
>>> 	0EC	OP_PAUSE	OPD
>>> 	118	IADDR1		IAUR
>>> 	11C	IADDR1		IALR
>>> 	120	GADDR1		GAUR
>>> 	124	GADDR2		GALR
>>> 	144	X_WMRK		FECTFWR
>>> 	184	RFIFO_DATA	FECRFDR
>>> 	188	RFIFO_STATUS	FECRFSR
>>> 	18C	RFIFO_CONTROL	FECRFCR
>>> 	190	RFIFO_LRF_PTR	FECRLRFP
>>> 	194	RFIFO_LWF_PTR	FECRLWFP
>>> 	198	RFIFO_ALARM	FECRFAR
>>> 	19C	RFIFO_RDPTR	FECRFRP
>>> 	1A0	RFIFO_WRPTR	FECRFWP
>>> 	1A4	TFIFO_DATA	FECTFDR
>>> 	1A8	TFIFO_STATUS	FECTFSR
>>> 	1AC	TFIFO_CONTROL	FECTFCR
>>> 	1B0	TFIFO_LRF_PTR	FECTLRFP
>>> 	1B4	TFIFO_LWF_PTR	FECTLWFP
>>> 	1B8	TFIFO_ALARM	FECTFAR
>>> 	1BC	TFIFO_RDPTR	FECTFRP
>>> 	1C0	TFIFO_WRPTR	FECTFWP
>>> 	1C4	RESET_CNTRL	FECFRST
>>> 	1C8	XMIT_FSM	FECCTCWR
>>>
>>>> Probably the best thing to do is post the patches on the linux kernel
>>>> mailing list then, asking for direction on a dma driver.
>>>>
>>>> I have no problem with it going into the arch/m68k area. So that is
>>>> always an option.
>>>
>>> For the dma engines, the similarity is also obvious.  For example, find
>>> below side by side mpc52xx and m54xx definitions for the
>>> main DMA registers :
>>>
>>> from mpc52xx.h				from MCD_dma.h
>>> /* SDMA */				/* MCD_DMA */
>>> struct mpc52xx_sdma {			struct dmaRegs {
>>>    u32 taskBar; /* 0x00 */		        u32 taskbar;
>>>    u32 currentPointer; /* 0x04 */		        u32 currPtr;
>>>    u32 endPointer; /* 0x08 */		        u32 endPtr;
>>>    u32 variablePointer; /* 0x0c */	        u32 varTablePtr;
>>>
>>>    u8 IntVect1; /* 0x10 */		        u16 dma_rsvd0;
>>>    u8 IntVect2; /* 0x11 */
>>>    u16 PtdCntrl; /* 0x12 */		        u16 ptdControl;
>>>
>>>    u32 IntPend; /* 0x14 */		        u32 intPending;
>>>    u32 IntMask; /* 0x18 */		        u32 intMask;
>>>
>>>    u16 tcr[16]; /* 0x1c .. 0x3a */	        u16 taskControl[16];
>>>
>>>    u8 ipr[32]; /* 0x3c .. 0x5b */		        u8  priority[32];
>>>
>>>    u32 cReqSelect; /* 0x5c */		        u32 initiatorMux;
>>>    u32 task_size0; /* 0x60 */		        u32 taskSize0;
>>>    u32 task_size1; /* 0x64 */		        u32 taskSize1;
>>>    u32 MDEDebug; /* 0x68 */		        u32 dma_rsvd1;
>>>    u32 ADSDebug; /* 0x6c */		        u32 dma_rsvd2;
>>>    u32 Value1; /* 0x70 */			        u32 debugComp1;
>>>    u32 Value2; /* 0x74 */			        u32 debugComp2;
>>>    u32 Control; /* 0x78 */		        u32 debugControl;
>>>    u32 Status; /* 0x7c */			        u32 debugStatus;
>>>    u32 PTDDebug; /* 0x80 */		        u32 ptdDebug;
>>> };					};
>
>
>
>

-- 
------------------------------------------------------------------------
Greg Ungerer  --  Principal Engineer        EMAIL:     [email-masked]
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
8 Gardner Close                             FAX:         +61 7 3217 5323
Milton, QLD, 4064, Australia                WEB: http://www.SnapGear.com
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