linux-kernel - Re: [PATCH v2 01/13] dmaengine: pl330: Remove the burst limit for quirk 'NO-FLUSHP'

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Message-ID: <879c88ef-1d74-26d5-1641-efeb450362fa@rock-chips.com>
Date:   Mon, 29 Jun 2020 09:38:54 +0800
From:   sugar zhang <sugar.zhang@...k-chips.com>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Heiko Stuebner <heiko@...ech.de>,
        linux-rockchip@...ts.infradead.org,
        Dan Williams <dan.j.williams@...el.com>,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 01/13] dmaengine: pl330: Remove the burst limit for
 quirk 'NO-FLUSHP'


On 2020/6/24 15:54, Vinod Koul wrote:
> On 09-06-20, 09:14, Sugar Zhang wrote:
>> There is no reason to limit the performance on the 'NO-FLUSHP' SoCs,
>> cuz these platforms are just that the 'FLUSHP' instruction is broken.
> Lets not use terms like cuz... 'because' is perfect term :)
>
> It can rephrased to:
> There is no reason to limit the performance on the 'NO-FLUSHP' SoCs
> beacuse 'FLUSHP' instruction is broken on these platforms, so remove the
> limit to improve the efficiency
Thanks, I will send a v3 including these.
>
>> so, remove the limit to improve the efficiency.
>>
>> Signed-off-by: Sugar Zhang <sugar.zhang@...k-chips.com>
>> ---
>>
>> Changes in v2: None
>>
>>   drivers/dma/pl330.c | 34 ++++++++++++++++++++++------------
>>   1 file changed, 22 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
>> index 6a158ee..ff0a91f 100644
>> --- a/drivers/dma/pl330.c
>> +++ b/drivers/dma/pl330.c
>> @@ -1183,9 +1183,6 @@ static inline int _ldst_peripheral(struct pl330_dmac *pl330,
>>   {
>>   	int off = 0;
>>   
>> -	if (pl330->quirks & PL330_QUIRK_BROKEN_NO_FLUSHP)
>> -		cond = BURST;
>> -
>>   	/*
>>   	 * do FLUSHP at beginning to clear any stale dma requests before the
>>   	 * first WFP.
>> @@ -1231,8 +1228,9 @@ static int _bursts(struct pl330_dmac *pl330, unsigned dry_run, u8 buf[],
>>   }
>>   
>>   /*
>> - * transfer dregs with single transfers to peripheral, or a reduced size burst
>> - * for mem-to-mem.
>> + * only the unaligned bursts transfers have the dregs.
>> + * transfer dregs with a reduced size burst to peripheral,
>> + * or a reduced size burst for mem-to-mem.
> This is not related to broken flush and should be a different patch
> explaining why this changes were done
ok, I will split this patch in v3.
>>    */
>>   static int _dregs(struct pl330_dmac *pl330, unsigned int dry_run, u8 buf[],
>>   		const struct _xfer_spec *pxs, int transfer_length)
>> @@ -1247,8 +1245,23 @@ static int _dregs(struct pl330_dmac *pl330, unsigned int dry_run, u8 buf[],
>>   	case DMA_MEM_TO_DEV:
>>   		/* fall through */
>>   	case DMA_DEV_TO_MEM:
>> -		off += _ldst_peripheral(pl330, dry_run, &buf[off], pxs,
>> -			transfer_length, SINGLE);
>> +		/*
>> +		 * dregs_len = (total bytes - BURST_TO_BYTE(bursts, ccr)) /
>> +		 *             BRST_SIZE(ccr)
>> +		 * the dregs len must be smaller than burst len,
>> +		 * so, for higher efficiency, we can modify CCR
>> +		 * to use a reduced size burst len for the dregs.
>> +		 */
>> +		dregs_ccr = pxs->ccr;
>> +		dregs_ccr &= ~((0xf << CC_SRCBRSTLEN_SHFT) |
>> +			(0xf << CC_DSTBRSTLEN_SHFT));
>> +		dregs_ccr |= (((transfer_length - 1) & 0xf) <<
>> +			CC_SRCBRSTLEN_SHFT);
>> +		dregs_ccr |= (((transfer_length - 1) & 0xf) <<
>> +			CC_DSTBRSTLEN_SHFT);
>> +		off += _emit_MOV(dry_run, &buf[off], CCR, dregs_ccr);
>> +		off += _ldst_peripheral(pl330, dry_run, &buf[off], pxs, 1,
>> +					BURST);
>>   		break;
>>   
>>   	case DMA_MEM_TO_MEM:
>> @@ -2221,9 +2234,7 @@ static bool pl330_prep_slave_fifo(struct dma_pl330_chan *pch,
>>   
>>   static int fixup_burst_len(int max_burst_len, int quirks)
>>   {
>> -	if (quirks & PL330_QUIRK_BROKEN_NO_FLUSHP)
>> -		return 1;
>> -	else if (max_burst_len > PL330_MAX_BURST)
>> +	if (max_burst_len > PL330_MAX_BURST)
>>   		return PL330_MAX_BURST;
>>   	else if (max_burst_len < 1)
>>   		return 1;
>> @@ -3128,8 +3139,7 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
>>   	pd->dst_addr_widths = PL330_DMA_BUSWIDTHS;
>>   	pd->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
>>   	pd->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
>> -	pd->max_burst = ((pl330->quirks & PL330_QUIRK_BROKEN_NO_FLUSHP) ?
>> -			 1 : PL330_MAX_BURST);
>> +	pd->max_burst = PL330_MAX_BURST;
>>   
>>   	ret = dma_async_device_register(pd);
>>   	if (ret) {
>> -- 
>> 2.7.4
>>
>>
--