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

[Jaehoon Chung <jh80.chung@samsung.com>]

On 09/11/2012 01:40 PM, Girish K S wrote:
> On 11 September 2012 10:06, Jaehoon Chung <jh80.chung@samsung.com> wrote:
>> On 09/11/2012 12:46 PM, Girish K S wrote:
>>> On 11 September 2012 07:53, Seungwon Jeon <tgih.jun@samsung.com> wrote:
>>>> This reverts commit 94c6cee91(Add check for IDMAC configuration).
>>>> Synopsys says that only if internal dmac is not present, optional
>>>> external dma interface is present. When internal dmac is present,
>>>> '0' value in DMA_INTERFACE of HCON is reasonable. DMA_INTERFACE
>>>> indicates external dma interface. And idmac initialization is
>>>> prohibited now. So, let's revert this commit.
>>>
>>> There is no register, or a field in any register which says IDMAC present.
>>> I can see only use_idmac bit field in CTRL register.
>>> So in first place how will i know whether IDMAC is present? Have you
>>> assumed that IDMAC is present.
>>> I would like to know without assuming, whether  IDMAC is present.
>>> If i have missed out something let me know.  i will check and revert back
>> I understood that if INTERNAL_DMAC at HCON register is set to 1, we didn't consdier the DMA_INTERFACE's value.
> I cannot see any field by name INTERNAL_DMAC in the HCON: can you
> please tell me the bit position of it.
> I think INTERNAL_DMAC is the signal interface to AXI master.
Sorry, You're right. there is no field for INTERNAL_DMAC at HCON register.
>> So although dma_interface is set to 0 or others, host can use the internal DMA.
>>
>> Best Regards,
>> Jaehoon Chung
>>>
>>>>
>>>> CC: Girish K S <girish.shivananjappa@linaro.org>
>>>> Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
>>>> ---
>>>>  drivers/mmc/host/dw_mmc.c |   15 ++-------------
>>>>  1 files changed, 2 insertions(+), 13 deletions(-)
>>>>
>>>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>>>> index 36f98c0..dcbe9aa 100644
>>>> --- a/drivers/mmc/host/dw_mmc.c
>>>> +++ b/drivers/mmc/host/dw_mmc.c
>>>> @@ -405,23 +405,11 @@ static void dw_mci_idmac_start_dma(struct dw_mci *host, unsigned int sg_len)
>>>>  static int dw_mci_idmac_init(struct dw_mci *host)
>>>>  {
>>>>         struct idmac_desc *p;
>>>> -       int i, dma_support;
>>>> +       int i;
>>>>
>>>>         /* Number of descriptors in the ring buffer */
>>>>         host->ring_size = PAGE_SIZE / sizeof(struct idmac_desc);
>>>>
>>>> -       /* Check if Hardware Configuration Register has support for DMA */
>>>> -       dma_support = (mci_readl(host, HCON) >> 16) & 0x3;
>>>> -
>>>> -       if (!dma_support || dma_support > 2) {
>>>> -               dev_err(&host->dev,
>>>> -                       "Host Controller does not support IDMA Tx.\n");
>>>> -               host->dma_ops = NULL;
>>>> -               return -ENODEV;
>>>> -       }
>>>> -
>>>> -       dev_info(&host->dev, "Using internal DMA controller.\n");
>>>> -
>>>>         /* Forward link the descriptor list */
>>>>         for (i = 0, p = host->sg_cpu; i < host->ring_size - 1; i++, p++)
>>>>                 p->des3 = host->sg_dma + (sizeof(struct idmac_desc) * (i + 1));
>>>> @@ -1895,6 +1883,7 @@ static void dw_mci_init_dma(struct dw_mci *host)
>>>>         /* Determine which DMA interface to use */
>>>>  #ifdef CONFIG_MMC_DW_IDMAC
>>>>         host->dma_ops = &dw_mci_idmac_ops;
>>>> +       dev_info(&host->dev, "Using internal DMA controller.\n");
>>>>  #endif
>>>>
>>>>         if (!host->dma_ops)
>>>> --
>>>> 1.7.0.4
>>>>
>>>>
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>>
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