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Date: Wed, 24 Dec 2014 20:06:25 +0000
From: James Hartley <James.Hartley@...tec.com>
To: Andrew Bresticker <abrestic@...omium.org>
CC: Vinod Koul <vinod.koul@...el.com>,
Dan Williams <dan.j.williams@...el.com>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
"Grant Likely" <grant.likely@...aro.org>,
James Hogan <James.Hogan@...tec.com>,
Ezequiel Garcia <Ezequiel.Garcia@...tec.com>,
Damien Horsley <Damien.Horsley@...tec.com>,
Arnd Bergmann <arnd@...db.de>,
"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 2/2] dmaengine: Add driver for IMG MDC
> On 24 Dec 2014, at 17:21, Andrew Bresticker <abrestic@...omium.org> wrote:
>
>> On Tue, Dec 23, 2014 at 9:22 PM, Vinod Koul <vinod.koul@...el.com> wrote:
>>> On Thu, Dec 11, 2014 at 02:59:17PM -0800, Andrew Bresticker wrote:
>>> Add support for the IMG Multi-threaded DMA Controller (MDC) found on
>>> certain IMG SoCs. Currently this driver supports the variant present
>>> on the MIPS-based Pistachio SoC.a
>
>> Overall looks okay. I also need some review by DT folks on the bindings
>
> Arnd has ack'ed the DT bindings, do you need someone else to review
> them as well?
>
>>> +static void mdc_list_desc_config(struct mdc_chan *mchan,
>>> + struct mdc_hw_list_desc *ldesc,
>>> + enum dma_transfer_direction dir,
>>> + dma_addr_t src, dma_addr_t dst, size_t len)
>>> +{
>>> + struct mdc_dma *mdma = mchan->mdma;
>>> + unsigned int max_burst, burst_size;
>>> +
>>> + ldesc->gen_conf = MDC_GENERAL_CONFIG_IEN | MDC_GENERAL_CONFIG_LIST_IEN |
>>> + MDC_GENERAL_CONFIG_LEVEL_INT | MDC_GENERAL_CONFIG_PHYSICAL_W |
>>> + MDC_GENERAL_CONFIG_PHYSICAL_R;
>>> + ldesc->readport_conf =
>>> + (mchan->thread << MDC_READ_PORT_CONFIG_STHREAD_SHIFT) |
>>> + (mchan->thread << MDC_READ_PORT_CONFIG_RTHREAD_SHIFT) |
>>> + (mchan->thread << MDC_READ_PORT_CONFIG_WTHREAD_SHIFT);
>>> + ldesc->read_addr = src;
>>> + ldesc->write_addr = dst;
>>> + ldesc->xfer_size = len - 1;
>>> + ldesc->node_addr = 0;
>>> + ldesc->cmds_done = 0;
>>> + ldesc->ctrl_status = MDC_CONTROL_AND_STATUS_LIST_EN |
>>> + MDC_CONTROL_AND_STATUS_EN;
>>> + ldesc->next_desc = NULL;
>>> +
>>> + if (IS_ALIGNED(dst, mdma->bus_width) &&
>>> + IS_ALIGNED(src, mdma->bus_width))
>>> + max_burst = mdma->bus_width * mdma->max_burst_mult;
>>> + else
>>> + max_burst = mdma->bus_width * (mdma->max_burst_mult - 1);
>>> +
>>> + if (dir == DMA_MEM_TO_DEV) {
>>> + ldesc->gen_conf |= MDC_GENERAL_CONFIG_INC_R;
>>> + ldesc->readport_conf |= MDC_READ_PORT_CONFIG_DREQ_ENABLE;
>>> + mdc_set_read_width(ldesc, mdma->bus_width);
>>> + mdc_set_write_width(ldesc, mchan->config.dst_addr_width);
>>> + burst_size = min(max_burst, mchan->config.dst_maxburst *
>>> + mchan->config.dst_addr_width);
>
>> why is this calculation done for burst size? Shouldn't we take the
>> config.dst_maxburst value configured by client?
>
> It's possible that the client could select a burst size that is too
> large (i.e. it exceeds the max_burst calculated above), so we cap it
> here to max_burst.
>
>>> +static struct dma_async_tx_descriptor *mdc_prep_slave_sg(
>>> + struct dma_chan *chan, struct scatterlist *sgl,
>>> + unsigned int sg_len, enum dma_transfer_direction dir,
>>> + unsigned long flags, void *context)
>>> +{
>>> + struct mdc_chan *mchan = to_mdc_chan(chan);
>>> + struct mdc_dma *mdma = mchan->mdma;
>>> + struct mdc_tx_desc *mdesc;
>>> + struct scatterlist *sg;
>>> + struct mdc_hw_list_desc *curr, *prev = NULL;
>>> + dma_addr_t curr_phys, prev_phys;
>>> + unsigned int i;
>>> +
>>> + if (!sgl)
>>> + return NULL;
>>> +
>>> + if (!is_slave_direction(dir))
>>> + return NULL;
>>> +
>>> + if (mdc_check_slave_width(mchan, dir) < 0)
>>> + return NULL;
>>> +
>>> + mdesc = kzalloc(sizeof(*mdesc), GFP_NOWAIT);
>>> + if (!mdesc)
>>> + return NULL;
>>> + mdesc->chan = mchan;
>>> +
>>> + for_each_sg(sgl, sg, sg_len, i) {
>>> + dma_addr_t buf = sg_dma_address(sg);
>>> + size_t buf_len = sg_dma_len(sg);
>>> +
>>> + while (buf_len > 0) {
>>> + size_t xfer_size;
>>> +
>>> + curr = dma_pool_alloc(mdma->desc_pool, GFP_NOWAIT,
>>> + &curr_phys);
>>> + if (!curr)
>>> + goto free_desc;
>>> +
>>> + if (!prev) {
>>> + mdesc->list_phys = curr_phys;
>>> + mdesc->list = curr;
>>> + } else {
>>> + prev->node_addr = curr_phys;
>>> + prev->next_desc = curr;
>>> + }
>>> +
>>> + xfer_size = min_t(size_t, mdma->max_xfer_size,
>>> + buf_len);
>>> +
>>> + if (dir == DMA_MEM_TO_DEV) {
>>> + mdc_list_desc_config(mchan, curr, dir, buf,
>>> + mchan->config.dst_addr,
>>> + xfer_size);
>>> + } else {
>>> + mdc_list_desc_config(mchan, curr, dir,
>>> + mchan->config.src_addr,
>>> + buf, xfer_size);
>>> + }
>>> +
>>> + prev = curr;
>>> + prev_phys = curr_phys;
>>> +
>>> + mdesc->list_len++;
>>> + mdesc->list_xfer_size += xfer_size;
>>> + buf += xfer_size;
>>> + buf_len -= xfer_size;
>
>> i see this pattern is repeat in all the .prepare calls, can we make it bit
>> generic and use that in the these three calls..
>
> I've pulled out almost all of the common stuff into
> mdc_list_desc_config(). I suppose the list manipulation could be
> moved there as well, but the rest is all slightly different in each
> case.
>
>>> + dma_cap_zero(mdma->dma_dev.cap_mask);
>>> + dma_cap_set(DMA_SLAVE, mdma->dma_dev.cap_mask);
>>> + dma_cap_set(DMA_PRIVATE, mdma->dma_dev.cap_mask);
>>> + dma_cap_set(DMA_CYCLIC, mdma->dma_dev.cap_mask);
>
>> and you dont seen to support pause/resume, though not a blocker but is it
>> not supported in HW or driver doesn't?
>
> Someone from IMG can correct me if I'm wrong, but I don't think the HW
> supports it.
Pause / resume is not supported by the MDC hardware.
James. --
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