Hi Vinod,
Thanks for the feedback.
> Subject: Re: [PATCH v4 2/4] drivers: dma: sh: Add DMAC driver for RZ/G2L
> SoC
>
> On 19-07-21, 10:25, Biju Das wrote:
>
> > +struct rz_dmac_chan {
> > + struct virt_dma_chan vc;
> > + void __iomem *ch_base;
> > + void __iomem *ch_cmn_base;
> > + unsigned int index;
> > + int irq;
> > + struct rz_dmac_desc *desc;
> > + int descs_allocated;
> > +
> > + enum dma_slave_buswidth src_word_size;
> > + enum dma_slave_buswidth dst_word_size;
> > + dma_addr_t src_per_address;
> > + dma_addr_t dst_per_address;
> > +
> > + u32 chcfg;
> > + u32 chctrl;
> > + int mid_rid;
> > +
> > + struct list_head ld_free;
> > + struct list_head ld_queue;
> > + struct list_head ld_active;
> > +
> > + struct {
> > + struct rz_lmdesc *base;
> > + struct rz_lmdesc *head;
> > + struct rz_lmdesc *tail;
> > + int valid;
> > + dma_addr_t base_dma;
> > + } lmdesc;
>
> should this be not part of rz_dmac_desc than channel?
No. It is channel specific. A channel has 64 HW legacy descriptors(see rz_dmac_chan_probe function) and 16 rz_dmac_desc( see rz_dmac_chan_resources function)
> > +static int rz_dmac_config(struct dma_chan *chan,
> > + struct dma_slave_config *config) {
> > + struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
> > + u32 *ch_cfg;
> > +
> > + channel->src_per_address = config->src_addr;
> > + channel->src_word_size = config->src_addr_width;
> > + channel->dst_per_address = config->dst_addr;
> > + channel->dst_word_size = config->dst_addr_width;
> > +
> > + if (config->peripheral_config) {
> > + ch_cfg = config->peripheral_config;
> > + channel->chcfg = *ch_cfg;
> > + }
>
> can you explain what this the ch_cfg here and what does it represent?
It is a 32 bit value represent channel config value which supplied by each client driver during slave config.
It contains information like transfer mode,src/destination data size, Ack mode, Level type, DMA request on rising edge or falling
Edge, request direction etc...
For eg:- The channel config for SSI tx is (0x11228).
An example usage can be found here [1]
[1] https://patchwork.kernel.org/project/linux-renesas-soc/patch/20210719134040.7964-8-biju.das.jz@xxxxxxxxxxxxxx/
Regards,
Biju
>
> --
> ~Vinod
