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Subject: Re: [PATCH v7 06/12] dmaengine: ti: Add cppi5 header for K3
 NAVSS/UDMA
To:     Vinod Koul <vkoul@kernel.org>
CC:     <robh+dt@kernel.org>, <nm@ti.com>, <ssantosh@kernel.org>,
        <dan.j.williams@intel.com>, <dmaengine@vger.kernel.org>,
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        <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <grygorii.strashko@ti.com>, <lokeshvutla@ti.com>,
        <t-kristo@ti.com>, <tony@atomide.com>, <j-keerthy@ti.com>,
        <vigneshr@ti.com>
References: <20191209094332.4047-1-peter.ujfalusi@ti.com>
 <20191209094332.4047-7-peter.ujfalusi@ti.com>
 <20191220095455.GM2536@vkoul-mobl>
From:   Peter Ujfalusi <peter.ujfalusi@ti.com>
Message-ID: <d5bd6bcf-9c1e-8633-fdc4-ee787100b44c@ti.com>
Date:   Fri, 20 Dec 2019 12:42:10 +0200
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Hi Vinod,

On 20/12/2019 11.54, Vinod Koul wrote:
> On 09-12-19, 11:43, Peter Ujfalusi wrote:
> 
>> +#define CPPI5_INFO2_DESC_RETPUSHPOLICY		BIT(16)
>> +#define CPPI5_INFO2_DESC_RETP_MASK		GENMASK(18, 16)
>> +
>> +#define CPPI5_INFO2_DESC_RETQ_SHIFT		(0)
>> +#define CPPI5_INFO2_DESC_RETQ_MASK		GENMASK(15, 0)
>> +
>> +#define CPPI5_INFO3_DESC_SRCTAG_SHIFT		(16U)
>> +#define CPPI5_INFO3_DESC_SRCTAG_MASK		GENMASK(31, 16)
>> +#define CPPI5_INFO3_DESC_DSTTAG_SHIFT		(0)
>> +#define CPPI5_INFO3_DESC_DSTTAG_MASK		GENMASK(15, 0)
>> +
>> +#define CPPI5_BUFINFO1_HDESC_DATA_LEN_SHIFT	(0)
>> +#define CPPI5_BUFINFO1_HDESC_DATA_LEN_MASK	GENMASK(27, 0)
>> +
>> +#define CPPI5_OBUFINFO0_HDESC_BUF_LEN_SHIFT	(0)
>> +#define CPPI5_OBUFINFO0_HDESC_BUF_LEN_MASK	GENMASK(27, 0)
> 
> I think you can remove the SHIFT defines and use ffs() to get the bit
> position for shift

Right. I'll convert to use ffs()

> 
>> +static inline u32 cppi5_hdesc_calc_size(bool epib, u32 psdata_size,
>> +					u32 sw_data_size)
>> +{
>> +	u32 desc_size;
>> +
>> +	if (psdata_size > CPPI5_INFO0_HDESC_PSDATA_MAX_SIZE)
>> +		return 0;
>> +
>> +	desc_size = sizeof(struct cppi5_host_desc_t) + psdata_size +
>> +		    sw_data_size;
> 
> I think there was an API for this kind of mem allocation of struct and
> buffer attached...

The returned size is not only used when allocating memory or setting up
the dma_pool, but for UDMAP's fetch size parameter.

>> +static inline void cppi5_hdesc_reset_hbdesc(struct cppi5_host_desc_t *desc)
>> +{
>> +	desc->hdr = (struct cppi5_desc_hdr_t) { 0 };
>> +	desc->next_desc = 0;
> 
> would this not be superfluous? Or if you want a memset call?

The intention is to reset the header and the next descriptor link but
leave the backing buffer information intact. This allows the reuse of a
descriptor+buffer and we only need to set the header bits + next
descriptor pointer if any.

>> +static inline u32 *cppi5_hdesc_get_psdata32(struct cppi5_host_desc_t *desc)
>> +{
>> +	return (u32 *)cppi5_hdesc_get_psdata(desc);
> 
> you dont need casts away from void *

Hrm, or just remove this, clients can use the cppi5_hdesc_get_psdata()
directly.


- Péter

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