Re: [PATCH v2 1/1] mmc: Support of DUAL BUFFER DESC[ring] mode for dw_mmc

[James Hogan <james.hogan@imgtec.com>]

Hi Shashidhar,

Has the patch been tested to check the dual buffer code gets hit (i.e.
it doesn't always get given just single buffers) and that it still works?

mmc_test might be a good way of doing so if you have a spare sd card
that you don't mind getting wiped, and I believe it does performance
measurements too which is a bonus.

Cheers
James

On 08/30/2011 10:23 AM, Shashidhar Hiremath wrote:
> Hi Kyungmin ,
>   I have actually not tested ,though I believe Dual Buffer Mode will
> improve performance by certain extent.The main reason for adding his
> patch is since the hardware supports different modes for IDMAC data
> transfer.I thought it would be better to have the support in the
> driver.I will surely comeback with statistics on performance
> improvement soon after testing it.
> 
> On Tue, Aug 30, 2011 at 2:05 PM, Kyungmin Park <kmpark@infradead.org> wrote:
>> Hi Shashidhar,
>>
>> Simple question, what's the performance or latency improvement by this patch?
>> IOW, what's the benefits? can you provide any performance results or
>> similar things?
>>
>> Thank you,
>> Kyungmin Park
>>
>> On Tue, Aug 30, 2011 at 5:29 PM, Shashidhar Hiremath
>> <shashidharh@vayavyalabs.com> wrote:
>>> This Patch adds the support for Dual Buffer Descriptor mode of
>>> Operation for the dw_mmc driver.The patch also provides the configurability
>>> Option for choosing DUAL_BUFFER mode or the chained modes through menuconfig.
>>> The Menuconfig option for selecting Dual Buffer mode or chained mode
>>> is selected only if Internal DMAC is enabled.
>>>
>>> Signed-off-by: Shashidhar Hiremath <shashidharh@vayavyalabs.com>
>>> ---
>>> v2:
>>> * As per suggestions by Will Newton and James Hogan
>>> -Config symbol Names prefixed with MMC_DW
>>> -Added more Description for Config parameters added
>>> -Removed unnecessary config opion IDMAC_DESC_MODE
>>> -IDMAC_SET_BUFFER_SIZE chenged IDMAC_SET_BUFFER_SIZES
>>> -fixed typos and indented commments correctly
>>> -if ((i +1) <= sg_len changed to ((i +1) < sg_len
>>> -duplication "desc->des0 = IDMAC_DES0_OWN | IDMAC_DES0_DIC" line removed
>>> -fixed bug in making DSL value zero
>>> -removed ANDing the des1 with zero before writing buffer lengths to it
>>> -Added proper multiline comments
>>> ---
>>>  drivers/mmc/host/Kconfig  |   19 +++++++++++++++++
>>>  drivers/mmc/host/dw_mmc.c |   49 +++++++++++++++++++++++++++++++++++---------
>>>  drivers/mmc/host/dw_mmc.h |    2 +
>>>  3 files changed, 60 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
>>> index 8c87096..1e20dfa 100644
>>> --- a/drivers/mmc/host/Kconfig
>>> +++ b/drivers/mmc/host/Kconfig
>>> @@ -534,6 +534,25 @@ config MMC_DW_IDMAC
>>>          Designware Mobile Storage IP block. This disables the external DMA
>>>          interface.
>>>
>>> +choice
>>> +       prompt "select  IDMAC Descriptors Mode"
>>> +       depends on MMC_DW_IDMAC
>>> +
>>> +config MMC_DW_CHAIN_DESC
>>> +       bool "Chain Descriptor Structure"
>>> +       help
>>> +         Select this option to enable Chained Mode of Operation and the
>>> +         Chained Mode operates in a mode where only one Buffer will be used
>>> +         for each descriptor when the transfer is happening in DMA mode.
>>> +
>>> +config MMC_DW_DUAL_BUFFER_DESC
>>> +       bool "Dual Buffer Descriptor Structure"
>>> +       help
>>> +         Select this option to enable Dual Buffer Desc Mode of Operation and
>>> +         Dual Buffer Descriptor Mode or the Ring Mode indicates that two
>>> +         buffers can be used for each descriptor during DMA mode transfer.
>>> +endchoice
>>> +
>>>  config MMC_SH_MMCIF
>>>        tristate "SuperH Internal MMCIF support"
>>>        depends on MMC_BLOCK && (SUPERH || ARCH_SHMOBILE)
>>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>>> index ff0f714..ee02208 100644
>>> --- a/drivers/mmc/host/dw_mmc.c
>>> +++ b/drivers/mmc/host/dw_mmc.c
>>> @@ -63,6 +63,9 @@ struct idmac_desc {
>>>        u32             des1;   /* Buffer sizes */
>>>  #define IDMAC_SET_BUFFER1_SIZE(d, s) \
>>>        ((d)->des1 = ((d)->des1 & 0x03ffe000) | ((s) & 0x1fff))
>>> +#define IDMAC_SET_BUFFER_SIZES(d, s1, s2) \
>>> +       ((d)->des1 = (((d)->des1)  | \
>>> +       (((s1) & 0x1fff) | ((s2) & 0x1fff << 13))))
>>>
>>>        u32             des2;   /* buffer 1 physical address */
>>>
>>> @@ -348,17 +351,38 @@ static void dw_mci_translate_sglist(struct dw_mci *host, struct mmc_data *data,
>>>        struct idmac_desc *desc = host->sg_cpu;
>>>
>>>        for (i = 0; i < sg_len; i++, desc++) {
>>> -               unsigned int length = sg_dma_len(&data->sg[i]);
>>> -               u32 mem_addr = sg_dma_address(&data->sg[i]);
>>> +               /* Length and mem_address of first buffer */
>>> +               unsigned int length1 = sg_dma_len(&data->sg[i]);
>>> +               u32 mem_addr1 = sg_dma_address(&data->sg[i]);
>>> +#ifdef CONFIG_DUAL_BUFFER_DESC
>>> +               unsigned int length2;
>>> +               u32 mem_addr2;
>>>
>>> -               /* Set the OWN bit and disable interrupts for this descriptor */
>>> +               /*
>>> +                * Set the OWN bit and disable interrupts
>>> +                * for this descriptor
>>> +                */
>>> +               desc->des0 = IDMAC_DES0_OWN | IDMAC_DES0_DIC
>>> +               if ((i+1) < sg_len) {
>>> +                       length2 = sg_dma_len(&data->sg[i+1]);
>>> +                       mem_addr2 = sg_dma_address(&data->sg[i+1]);
>>> +                       /* Buffer length being set for Buffer1 and Buffer2 */
>>> +                       IDMAC_SET_BUFFER_SIZES(desc, length1, length2);
>>> +                       desc->des3 = mem_addr2;
>>> +                       /* Incrementing for the second buffer */
>>> +                       i++;
>>> +               } else {
>>> +                       /* Buffer length being set for Buffer1 and Buffer2 */
>>> +                       IDMAC_SET_BUFFER_SIZES(desc, length1, 0);
>>> +               }
>>> +#elif CONFIG_CHAIN_DESC
>>> +               /* Set OWN bit and disable interrupts for this descriptor */
>>>                desc->des0 = IDMAC_DES0_OWN | IDMAC_DES0_DIC | IDMAC_DES0_CH;
>>> -
>>> -               /* Buffer length */
>>> -               IDMAC_SET_BUFFER1_SIZE(desc, length);
>>> -
>>> +               /* Buffer length for Buffer1 */
>>> +               IDMAC_SET_BUFFER1_SIZE(desc, length1);
>>> +#endif
>>>                /* Physical address to DMA to/from */
>>> -               desc->des2 = mem_addr;
>>> +               desc->des2 = mem_addr1;
>>>        }
>>>
>>>        /* Set first descriptor */
>>> @@ -369,6 +393,10 @@ static void dw_mci_translate_sglist(struct dw_mci *host, struct mmc_data *data,
>>>        desc = host->sg_cpu + (i - 1) * sizeof(struct idmac_desc);
>>>        desc->des0 &= ~(IDMAC_DES0_CH | IDMAC_DES0_DIC);
>>>        desc->des0 |= IDMAC_DES0_LD;
>>> +#ifdef CONFIG_DUAL_BUFFER_DESC
>>> +       /* Set the End of Ring bit */
>>> +       desc->des0 |= IDMAC_DES0_ER;
>>> +#endif
>>>
>>>        wmb();
>>>  }
>>> @@ -388,7 +416,8 @@ static void dw_mci_idmac_start_dma(struct dw_mci *host, unsigned int sg_len)
>>>
>>>        /* Enable the IDMAC */
>>>        temp = mci_readl(host, BMOD);
>>> -       temp |= SDMMC_IDMAC_ENABLE | SDMMC_IDMAC_FB;
>>> +       /* The Descriptor Skip length is made zero */
>>> +       temp |= SDMMC_IDMAC_ENABLE | SDMMC_IDMAC_FB | SDMMC_BMOD_DSL(0);
>>>        mci_writel(host, BMOD, temp);
>>>
>>>        /* Start it running */
>>> diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
>>> index 027d377..0520dc8 100644
>>> --- a/drivers/mmc/host/dw_mmc.h
>>> +++ b/drivers/mmc/host/dw_mmc.h
>>> @@ -72,6 +72,8 @@
>>>  /* Clock Enable register defines */
>>>  #define SDMMC_CLKEN_LOW_PWR            BIT(16)
>>>  #define SDMMC_CLKEN_ENABLE             BIT(0)
>>> +/* BMOD register defines */
>>> +#define SDMMC_BMOD_DSL(n)              _SBF(2, (n))
>>>  /* time-out register defines */
>>>  #define SDMMC_TMOUT_DATA(n)            _SBF(8, (n))
>>>  #define SDMMC_TMOUT_DATA_MSK           0xFFFFFF00
>>> --
>>> 1.7.2.3
>>>
>>> --
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>>
> 
> 
>