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

Girish K S
2012-09-11T07:14:23Z

On 11 September 2012 12:41, Girish K S <girish.shivananjappa@linaro.org> wrote:
> On 11 September 2012 12:09, Seungwon Jeon <tgih.jun@samsung.com> wrote:
>> On Tuesday, September 11, 2012, Girish K S <girish.shivananjappa@linaro.org> wrote:
>>> On 11 September 2012 11:16, Seungwon Jeon <tgih.jun@samsung.com> wrote:
>>> > On Tuesday, September 11, 2012, Girish K S <girish.shivananjappa@linaro.org> 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
>>> > There is no way to see the presence of idmac from host controller on the runtime.
>>> > But enabling idmac is not selected in the menuconfig just with assuming its presence.
>>> > User can find the support of idmac from manual at least, I know the lack of this information in
>>> manual though.
>>> I cannot find any line in the manual saying "Support IDMAC". Keeping
>>> this in mind and the with the literal meaning what the HCON field
>>> DMA_INTERFACE means, the above patch was made.
>>> i had posted a patch for adding quirk to this (was waiting for some dt
>>> patches to be accepted to resend it). Once that patch gets merged it
>>> will be helpful for the user to use it comfortably. If QUIRK is
>>> enabled it means there is IDMAC and the driver user is intentionally
>>> enabling it.
>> I mentioned the lack of description of feature in manual.
>> When we consider the real meaning of DMA_INTERFACE, '0' value doen't indicate the absence of idmac.
>> So, we cannot decide the support of idmac with the DMA_INTERFACE.
>>
>> Do you mean this patch:"mmc: dwmmc: Add quirk for broken Hardware Config"?
>> HCON register in the original Synopsys doesn't include information of internal dmac.
>> Do you think it's also broken?
> As per the current available information from the manual i think the
> HCON is broken.
> May be the synopsys is the right person to clarify this.
If you have some confirmation regarding the DMA_INTERFACE from the
synopsys. please post it, It will be really helpful in correcting my
understanding abt the dma interface
>>
>> Thanks,
>> Seungwon Jeon
>>>
>>> >
>>> > Thanks,
>>> > Seungwon Jeon
>>> >
>>> >>
>>> >> >
>>> >> > 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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>>