[PATCH 04/18] mmc: meson-gx: improve meson_mmc_start_cmd

[Heiner Kallweit]

Am 15.02.2017 um 18:04 schrieb Kevin Hilman:
> Heiner Kallweit <hkallweit1 at gmail.com> writes:
> 
>> Remove use of unneeded members cmd_arg and cmd_resp.
>> Setting SD_EMMC_CMD_RSP is only needed if CMD_CFG_RESP_NUM is set,
>> so don't write this register in all other cases.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1 at gmail.com>
> 
> I'm not sure I like this change.  This works now because there is only
> one descriptor used, but one of the next things to work on in this
> driver is taking advantage of the internal DMA capabilities, which means
> having a chain of descriptorsall filled out in memory.
> 
I implemented the descriptor chain mode and tests (together with CMD23
mode) resulted in 140 MB/s read performance (from a 128GB eMMC card).
So I will submit this extension together with the CMD23 mode extension.

Heiner

> Kevin
> 
>> ---
>>  drivers/mmc/host/meson-gx-mmc.c | 6 ++----
>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
>> index ece38b44..630e0590 100644
>> --- a/drivers/mmc/host/meson-gx-mmc.c
>> +++ b/drivers/mmc/host/meson-gx-mmc.c
>> @@ -456,7 +456,6 @@ static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
>>  	desc->cmd_cfg |= (cmd->opcode & CMD_CFG_CMD_INDEX_MASK)	<<
>>  		CMD_CFG_CMD_INDEX_SHIFT;
>>  	desc->cmd_cfg |= CMD_CFG_OWNER;  /* owned by CPU */
>> -	desc->cmd_arg = cmd->arg;
>>  
>>  	/* Response */
>>  	if (cmd->flags & MMC_RSP_PRESENT) {
>> @@ -464,7 +463,7 @@ static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
>>  		if (cmd->flags & MMC_RSP_136)
>>  			desc->cmd_cfg |= CMD_CFG_RESP_128;
>>  		desc->cmd_cfg |= CMD_CFG_RESP_NUM;
>> -		desc->cmd_resp = 0;
>> +		writel(0, host->regs + SD_EMMC_CMD_RSP);
>>  
>>  		if (!(cmd->flags & MMC_RSP_CRC))
>>  			desc->cmd_cfg |= CMD_CFG_RESP_NOCRC;
>> @@ -540,9 +539,8 @@ static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
>>  	desc->cmd_cfg |= CMD_CFG_END_OF_CHAIN;
>>  	writel(desc->cmd_cfg, host->regs + SD_EMMC_CMD_CFG);
>>  	writel(desc->cmd_data, host->regs + SD_EMMC_CMD_DAT);
>> -	writel(desc->cmd_resp, host->regs + SD_EMMC_CMD_RSP);
>>  	wmb(); /* ensure descriptor is written before kicked */
>> -	writel(desc->cmd_arg, host->regs + SD_EMMC_CMD_ARG);
>> +	writel(cmd->arg, host->regs + SD_EMMC_CMD_ARG);
>>  }
>>  
>>  static void meson_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
>