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

Girish K S
2012-09-11T04:41:00Z

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.
> 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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>