Re: [PATCH 2/2] DMA: Freescale: update driver to support 8-channel DMA engine

Hongbo Zhang
2013-07-03T03:47:58Z

On 07/03/2013 07:13 AM, Scott Wood wrote:
> On 06/30/2013 10:46:18 PM, hongbo.zhang@freescale.com wrote:
>> From: Hongbo Zhang <hongbo.zhang@freescale.com>
>>
>> This patch adds support to 8-channel DMA engine, thus the driver
>> works for both
>> the new 8-channel and the legacy 4-channel DMA engines.
>>
>> Signed-off-by: Hongbo Zhang <hongbo.zhang@freescale.com>
>> ---
>> drivers/dma/fsldma.c | 48
>> ++++++++++++++++++++++++++++++++++--------------
>> drivers/dma/fsldma.h | 4 ++--
>> 2 files changed, 36 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
>> index 4fc2980..0f453ea 100644
>> --- a/drivers/dma/fsldma.c
>> +++ b/drivers/dma/fsldma.c
>> @@ -1119,27 +1119,33 @@ static irqreturn_t fsldma_ctrl_irq(int irq,
>> void *data)
>> struct fsldma_device *fdev = data;
>> struct fsldma_chan *chan;
>> unsigned int handled = 0;
>> - u32 gsr, mask;
>> + u8 chan_sr[round_up(FSL_DMA_MAX_CHANS_PER_DEVICE, 4)];
>> + u32 gsr;
>> int i;
>>
>> - gsr = (fdev->feature & FSL_DMA_BIG_ENDIAN) ? in_be32(fdev->regs)
>> - : in_le32(fdev->regs);
>> - mask = 0xff000000;
>> - dev_dbg(fdev->dev, "IRQ: gsr 0x%.8x\n", gsr);
>> + memset(&chan_sr, 0, sizeof(chan_sr));
>> + gsr = (fdev->feature & FSL_DMA_BIG_ENDIAN) ? in_be32(fdev->regs0)
>> + : in_le32(fdev->regs0);
>> + memcpy(&chan_sr[0], &gsr, 4);
>> + dev_dbg(fdev->dev, "IRQ: gsr0 0x%.8x\n", gsr);
>> +
>> + if (of_device_is_compatible(fdev->dev->of_node,
>> "fsl,eloplus-dma2")) {
>
> NACK; Figure out what sort of device you've got when you first probe
> the device, and store the information for later. Do not call device
> tree stuff in an interrupt handler.
>
>> + gsr = (fdev->feature & FSL_DMA_BIG_ENDIAN) ?
>> + in_be32(fdev->regs1) : in_le32(fdev->regs1);
>> + memcpy(&chan_sr[4], &gsr, 4);
>> + dev_dbg(fdev->dev, "IRQ: gsr1 0x%.8x\n", gsr);
>> + }
>
> Do these memcpy()s get inlined? If not (and maybe even if they do),
> it'd be better to use a union instead.
>
For this and the first comments: good catches, thank you.
But it is very likely I will remove these codes, see the last comments
of yours and mine.
> Wait a second -- how are we even getting into this code on these new
> DMA controllers? All 85xx-family DMA controllers use fsldma_chan_irq
> directly.
>
Right, we are using fsldma_chan_irq, this code never run.
I just see there is such code for elo/eloplus DMA controllers, so I
update it for the new 8-channel DMA.
>> @@ -1341,13 +1349,22 @@ static int fsldma_of_probe(struct
>> platform_device *op)
>> INIT_LIST_HEAD(&fdev->common.channels);
>>
>> /* ioremap the registers for use */
>> - fdev->regs = of_iomap(op->dev.of_node, 0);
>> - if (!fdev->regs) {
>> - dev_err(&op->dev, "unable to ioremap registers\n");
>> + fdev->regs0 = of_iomap(op->dev.of_node, 0);
>> + if (!fdev->regs0) {
>> + dev_err(&op->dev, "unable to ioremap register0\n");
>> err = -ENOMEM;
>> goto out_free_fdev;
>> }
>>
>> + if (of_device_is_compatible(op->dev.of_node, "fsl,eloplus-dma2")) {
>
> Not "fsl,eloplusplus-dma"? :-)
>
> More seriously, if we're sticking with this "elo" naming, maybe
> "fsl,elo3-dma" would be better. It would be odd to have "2" in the
> name of the third generation of this hardware.
>
It was really hard for me to name this new controller.
Yes "fsl,elo3-dma" seems better.
>> diff --git a/drivers/dma/fsldma.h b/drivers/dma/fsldma.h
>> index f5c3879..880664d 100644
>> --- a/drivers/dma/fsldma.h
>> +++ b/drivers/dma/fsldma.h
>> @@ -112,10 +112,10 @@ struct fsldma_chan_regs {
>> };
>>
>> struct fsldma_chan;
>> -#define FSL_DMA_MAX_CHANS_PER_DEVICE 4
>> +#define FSL_DMA_MAX_CHANS_PER_DEVICE 8
>>
>> struct fsldma_device {
>> - void __iomem *regs; /* DGSR register base */
>> + void __iomem *regs0, *regs1; /* DGSR registers */
>
> Either give these meaningful names, or use an array. Or both (dgsr[2]).
>
> Or just get rid of this, since I don't see why we need DGSR1 at all,
> as previously noted.
>
I choose the names regs* just to follow the previous pattern.

Here comes the key point: both the previous DGSR and the new DGSR0/DGSR1
are not actually used because we are using per channel irq.
I see we had such codes to handle DGSR, so I just follow the same
pattern to handle the new DGSR0/DGSR1.
Since getting rid of this unused DGSR1 is permitted, I'd like to remove
all the related codes, then this patch becomes simple :)

> -Scott