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

[Seungwon Jeon <tgih.jun@samsung.com>]

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.

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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