Re: [PATCH] mmc: dw_mmc: Add check for IDMAC configuration

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On 12 June 2012 15:05, Will Newton <will.newton@xxxxxxxxx> wrote:
> On Tue, Jun 12, 2012 at 10:01 AM, Girish K S
> <girish.shivananjappa@xxxxxxxxxx> wrote:
>> On 12 June 2012 14:25, Will Newton <will.newton@xxxxxxxxx> wrote:
>>> On Tue, Jun 12, 2012 at 5:21 AM, Girish K S
>>> <girish.shivananjappa@xxxxxxxxxx> wrote:
>>>>
>>>> In the Current dwmmc driver there is support for selecting IDMAC from
>>>> the menu config option. If the support for IDMAC is enabled in the menu
>>>> config and Hardware configuration register's DMA_INTERFACE field is 0.
>>>> Still the driver will try to do the DMA initialization.
>>>>
>>>> The dw_mci_idmac_init function currently implemented returns only success
>>>> indicating that the DMA initialization is always successful. The current
>>>> patch will add a ciheck for existance of the DMA IP and allow the
>>>> DMA initialization.
>>>>
>>>> Signed-off-by: Girish K S <girish.shivananjappa@xxxxxxxxxx>
>>>> ---
>>>>  drivers/mmc/host/dw_mmc.c |   11 ++++++++++-
>>>>  1 files changed, 10 insertions(+), 1 deletions(-)
>>>
>>> This looks ok in principle. I'm wondering if we should only allow
>>> dma_support == 0x01 (DW_DMA) in the IDMAC case? It's not clear from
>>> the TRM what each of the DMA values means and I only have a system
>>> with external DMA support at the moment.
>> My understanding from the TRM
>> if dma_support =1; then use designware dma ip for internal
>> dma_support =2 then use any generic dma ip for internal dma tx
>> this config is only for IDMA support. If there is a external DMA CTRL
>> register should be used explicitly to enable DMA (there is no config
>> available to tell external dma supported). correct me if i am wrong.
>
> That sounds like a reasonable interpretation of the TRM. ;-)
>
> Acked-by: Will Newton <will.newton@xxxxxxxxxx>
I will resend the patch with minor change so that kernel doesnt crash
but use PIO mode and continue even if IDMAC is enabled accidentally.
what s your say?
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