Re: [PATCH v2] mmc: meson-gx: fix mmc dma operation

[Nan Li]

On 2019/11/5 21:30, Jerome Brunet wrote:
> 
> On Tue 05 Nov 2019 at 10:05, Nan Li <Nan.Li@xxxxxxxxxxx> wrote:
> 
> Nan Li, please fix your mailer to use plain text properly, your reply
> are near impossible to read
> 
Sorry, maybe there is something wrong with my email address. Please help 
me check whether my reply is in accordance with the format.

>> å 2019/11/5 16:54, Jerome Brunet åé:
>>
>>
>> On Tue 05 Nov 2019 at 09:30, Nan Li <Nan.Li@xxxxxxxxxxx><mailto:Nan.Li@xxxxxxxxxxx> wrote:
>>
>>
>>
>>
>>
>> Based on Uffe comment I tried something else.
>>
>> Basically, it enables chained mode in the driver only when the framework
>> calls pre/post_req callback. As far as understood, the framework calls
>> this when there is more than one request pending ... which seems to be
>> when chained mode actually make sense
>>
>> Jerome, what you are talking about is the system framework problem when you call pre/post_req,
>>
>> which is not related to the patch I submitted.
>>
>>
>>
>> I strongly disagree.
>> As far as I understand from your description, the problem was with the
>> life cycle of the dma mapping. This is tighly related with pre/post req.
>> Just the variable names you have picked clearly show that.
>>
>>
>>
>> As you said, pre/post_req is called only when there is data to implement the chained mode,
>>
>> but it is also possible to cause memory consistency problems,
>> resulting in incorrect data.
>>
>>
>>
>> The life cycle of the mapping is also taken care of with patch,
>> since dma mapping is no longer handled in .request(). IOW the mapping,
>> if any, will be released after the request is done using .post_req()
>>
>> If you think otherwise, please elaborate.
>>
>>
>> I see what you mean. You want to pull the pre/post_req operation out of the request interface and invoke it at the top.
>>
>> I didn't notice the following modification of patch in your last email and reply in time. I'm really sorry.
>>
>> The following patch removes all pre/post_req operations,
>>
>>
>>
>> No it does not. Callbacks are still provided to the MMC framework.
>>
>>
>>
>> but you do not send out the operation patch added to the upper layer
>> together.
>>
>>
>>
>> There is no modification needed in the upper layer
>>
>>
>>
>>
>> Then the patch is incomplete, which will affect the dma data transfer function in start_cmd function and affect the multi-block write operation.
>>
>>
>>
>>
>> No it is not incomplete. pre and post request are correctly called. You
>> can check that with ftrace if you want.
>>
>> Maybe you could try it ?
>>
>>
>> I'm sorry, I didn't catch your meaning.How do I use pre/post_req
>> properly?
> 
> Those callbacks are provided to the framework as well. If you have
> trouble following, please apply the patch and look at the driver
> 
> Have a look at "meson_mmc_ops"
> 
>>
>> Do you mean I need to add a call to pre/post_req on top of the changes
>> you provided below?
> 
> No, you should not
> 
>>
>> If not, your changes have deleted all pre/post_req calls.
> 
> No, it does not. It relies on the framework to activate the chained mode
> or not. Again, if you have trouble following you can try to enable
> ftrace and trace the mmc functions.
> 
>>
>>
>>
>>
>> Please send your complete patch, including core layer modification,
>> thank you.
>>
>>
>>
>>
>>
>> Therefore, this patch is added to make memory consistent and obtain real effective information.
>>
>>
>>
>> ----8<-----
>> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
>> index e712315c7e8d..399604b4124d 100644
>> --- a/drivers/mmc/host/meson-gx-mmc.c
>> +++ b/drivers/mmc/host/meson-gx-mmc.c
>> @@ -126,8 +126,7 @@
>>   #define SD_EMMC_CFG_CMD_GAP 16 /* in clock cycles */
>>   #define SD_EMMC_DESC_BUF_LEN PAGE_SIZE
>>
>> -#define SD_EMMC_PRE_REQ_DONE BIT(0)
>> -#define SD_EMMC_DESC_CHAIN_MODE BIT(1)
>> +#define SD_EMMC_DESC_CHAIN_MODE BIT(0)
>>
>>   #define MUX_CLK_NUM_PARENTS 2
>>
>> @@ -228,7 +227,6 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
>>          struct mmc_data *data = mrq->data;
>>          struct scatterlist *sg;
>>          int i;
>> -       bool use_desc_chain_mode = true;
>>
>>          /*
>>           * When Controller DMA cannot directly access DDR memory, disable
>> @@ -251,12 +249,11 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
>>                  /* check for 8 byte alignment */
>>                  if (sg->offset & 7) {
>>                          WARN_ONCE(1, "unaligned scatterlist buffer\n");
>> -                       use_desc_chain_mode = false;
>> -                       break;
>> +                       return;
>>                  }
>>
>> -       if (use_desc_chain_mode)
>> -               data->host_cookie |= SD_EMMC_DESC_CHAIN_MODE;
>> +       /* The planets are aligned, let's chain them up */
>> +       data->host_cookie |= SD_EMMC_DESC_CHAIN_MODE;
>>   }
>>
>>   static inline bool meson_mmc_desc_chain_mode(const struct mmc_data *data)
>> @@ -278,7 +275,6 @@ static void meson_mmc_pre_req(struct mmc_host *mmc, struct mmc_request *mrq)
>>                  return;
>>
>>          meson_mmc_get_transfer_mode(mmc, mrq);
>> -       data->host_cookie |= SD_EMMC_PRE_REQ_DONE;
>>
>>          if (!meson_mmc_desc_chain_mode(data))
>>                  return;
>> @@ -803,25 +799,11 @@ static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
>>   static void meson_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
>>   {
>>          struct meson_host *host = mmc_priv(mmc);
>> -       bool needs_pre_post_req = mrq->data &&
>> -                       !(mrq->data->host_cookie & SD_EMMC_PRE_REQ_DONE);
>> -
>> -       if (needs_pre_post_req) {
>> -               meson_mmc_get_transfer_mode(mmc, mrq);
>> -               if (!meson_mmc_desc_chain_mode(mrq->data))
>> -                       needs_pre_post_req = false;
>> -       }
>> -
>> -       if (needs_pre_post_req)
>> -               meson_mmc_pre_req(mmc, mrq);
>>
>>          /* Stop execution */
>>          writel(0, host->regs + SD_EMMC_START);
>>
>>          meson_mmc_start_cmd(mmc, mrq->sbc ?: mrq->cmd);
>> -
>> -       if (needs_pre_post_req)
>> -               meson_mmc_post_req(mmc, mrq, 0);
>>   }
>>
>>   static void meson_mmc_read_resp(struct mmc_host *mmc, struct mmc_command *cmd)
>> ---->8-----
>>
>> No performance hit AFAICT.
>>  From your description, it should address your problem too.
>>
>>
>>
>>
>> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
>> index e712315..7667e8a 100644
>> --- a/drivers/mmc/host/meson-gx-mmc.c
>> +++ b/drivers/mmc/host/meson-gx-mmc.c
>> @@ -173,6 +173,7 @@ struct meson_host {
>>          int irq;
>>
>>          bool vqmmc_enabled;
>> +       bool needs_pre_post_req;
>>   };
>>
>>   #define CMD_CFG_LENGTH_MASK GENMASK(8, 0)
>> @@ -654,6 +655,8 @@ static void meson_mmc_request_done(struct mmc_host *mmc,
>>          struct meson_host *host = mmc_priv(mmc);
>>
>>          host->cmd = NULL;
>> +       if (host->needs_pre_post_req)
>> +               meson_mmc_post_req(mmc, mrq, 0);
>>          mmc_request_done(host->mmc, mrq);
>>   }
>>
>> @@ -803,25 +806,23 @@ static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
>>   static void meson_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
>>   {
>>          struct meson_host *host = mmc_priv(mmc);
>> -       bool needs_pre_post_req = mrq->data &&
>> +
>> +       host->needs_pre_post_req = mrq->data &&
>>                          !(mrq->data->host_cookie & SD_EMMC_PRE_REQ_DONE);
>>
>> -       if (needs_pre_post_req) {
>> +       if (host->needs_pre_post_req) {
>>                  meson_mmc_get_transfer_mode(mmc, mrq);
>>                  if (!meson_mmc_desc_chain_mode(mrq->data))
>> -                       needs_pre_post_req = false;
>> +                       host->needs_pre_post_req = false;
>>          }
>>
>> -       if (needs_pre_post_req)
>> +       if (host->needs_pre_post_req)
>>                  meson_mmc_pre_req(mmc, mrq);
>>
>>          /* Stop execution */
>>          writel(0, host->regs + SD_EMMC_START);
>>
>>          meson_mmc_start_cmd(mmc, mrq->sbc ?: mrq->cmd);
>> -
>> -       if (needs_pre_post_req)
>> -               meson_mmc_post_req(mmc, mrq, 0);
>>   }
>>
>>   static void meson_mmc_read_resp(struct mmc_host *mmc, struct mmc_command *cmd)
>