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

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

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.
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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