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Date:	Fri, 25 Jul 2014 05:07:29 +0100
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Stephen Boyd <sboyd@...eaurora.org>
CC:	linux-mmc@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Chris Ball <chris@...ntf.net>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org, agross@...eaurora.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2] mmc: mmci: Add qcom dml support to the driver.



On 23/07/14 23:58, Stephen Boyd wrote:
> On 07/18/14 13:53, Srinivas Kandagatla wrote:
>>
>> @@ -468,6 +473,11 @@ static void mmci_dma_setup(struct mmci_host *host)
>>   		if (max_seg_size < host->mmc->max_seg_size)
>>   			host->mmc->max_seg_size = max_seg_size;
>>   	}
>> +
>> +	if (variant->qcom_dml && host->dma_rx_channel && host->dma_tx_channel) {
>> +		if (dml_hw_init(host, host->mmc->parent->of_node))
>> +			variant->qcom_dml = false;
>> +	}
>
> Style nit: Braces aren't needed.
Will fix it in next spin.
>
>> +
>> +void dml_start_xfer(struct mmci_host *host, struct mmc_data *data)
>> +{
>> +	u32 config;
>> +	void __iomem *base = host->base + DML_OFFSET;
>> +
>> +	if (data->flags & MMC_DATA_READ) {
>> +		/* Read operation: configure DML for producer operation */
>> +		/* Set producer CRCI-x and disable consumer CRCI */
>> +		config = readl_relaxed(base + DML_CONFIG);
>> +		config = (config & ~PRODUCER_CRCI_MSK) | PRODUCER_CRCI_X_SEL;
>> +		config = (config & ~CONSUMER_CRCI_MSK) | CONSUMER_CRCI_DISABLE;
>> +		writel_relaxed(config, base + DML_CONFIG);
>> +
>> +		/* Set the Producer BAM block size */
>> +		writel_relaxed(data->blksz, base + DML_PRODUCER_BAM_BLOCK_SIZE);
>> +
>> +		/* Set Producer BAM Transaction size */
>> +		writel_relaxed(data->blocks * data->blksz,
>> +			       base + DML_PRODUCER_BAM_TRANS_SIZE);
>> +		/* Set Producer Transaction End bit */
>> +		config = readl_relaxed(base + DML_CONFIG);
>> +		config |= PRODUCER_TRANS_END_EN;
>> +		writel_relaxed(config, base + DML_CONFIG);
>> +		/* Trigger producer */
>> +		writel_relaxed(1, base + DML_PRODUCER_START);
>> +	} else {
>> +		/* Write operation: configure DML for consumer operation */
>> +		/* Set consumer CRCI-x and disable producer CRCI*/
>> +		config = readl_relaxed(base + DML_CONFIG);
>> +		config = (config & ~CONSUMER_CRCI_MSK) | CONSUMER_CRCI_X_SEL;
>> +		config = (config & ~PRODUCER_CRCI_MSK) | PRODUCER_CRCI_DISABLE;
>> +		writel_relaxed(config, base + DML_CONFIG);
>> +		/* Clear Producer Transaction End bit */
>> +		config = readl_relaxed(base + DML_CONFIG);
>> +		config &= ~PRODUCER_TRANS_END_EN;
>> +		writel_relaxed(config, base + DML_CONFIG);
>> +		/* Trigger consumer */
>> +		writel_relaxed(1, base + DML_CONSUMER_START);
>> +	}
>
> I think we need a memory barrier here. Does the DML need to be enabled
> before the mmci driver sets MCI_DPSM_DMAENABLE? My understanding is that
> relaxed accesses to different devices aren't ordered with respect to one
> another.  So not having a memory barrier here could cause the
> consumer/producer to be enabled after MCI_DPSM_DMAENABLE is set in the
> mmci hardware. Downstream I see that we have an mb(), but I think we
> could just a wmb() because we're just ordering with the mmci hardware right?
yes, I think wmb should work. I will fix this.

>
> Is there any ordering required between bam and dml? I think enabling bam
> could happen after enabling the consumer unless we had a wmb() after we
> kick off bam and before we write a 1 to DML_CONSUMER_START.
>
Am not sure if there is any strict ordering requirement between bam and 
dml. But I can see a wmb in bam_start_dma().

>> +}
>> +
>> +static int of_get_dml_pipe_index(struct device_node *np, const char *name)
>
> return type of u32?
>
This function is expected to return negative error codes. I think I 
should change u32 to int in dml_hw_init().

>> +{
>> +	int index;
>> +	struct of_phandle_args	dma_spec;
>> +
>> +	index = of_property_match_string(np, "dma-names", name);
>> +
>> +	if (index < 0)
>> +		return -ENODEV;
>> +
>> +	if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
>> +				       &dma_spec))
>> +		return -ENODEV;
>> +
>> +	if (dma_spec.args_count)
>> +		return dma_spec.args[0];
>> +
>> +	return -ENODEV;
>> +}
>
> Much cleaner!
>
>> +
>> +/* Initialize the dml hardware connected to SD Card controller */
>> +int dml_hw_init(struct mmci_host *host, struct device_node *np)
>> +{
>> +	u32 config;
>> +	void __iomem *base;
>> +	u32 consumer_id, producer_id;
>> +
>> +	consumer_id = of_get_dml_pipe_index(np, "tx");
>> +	producer_id = of_get_dml_pipe_index(np, "rx");
>> +
>> +	if (producer_id < 0 || consumer_id < 0)
>> +		return -ENODEV;
>> +
>> +	base = host->base + DML_OFFSET;
>> +
>> +	/* Reset the DML block */
>> +	writel_relaxed(1, base + DML_SW_RESET);
>> +
>> +	/* Disable the producer and consumer CRCI */
>> +	config = (PRODUCER_CRCI_DISABLE | CONSUMER_CRCI_DISABLE);
>> +	/*
>> +	 * Disable the bypass mode. Bypass mode will only be used
>> +	 * if data transfer is to happen in PIO mode and don't
>> +	 * want the BAM interface to connect with SDCC-DML.
>> +	 */
>> +	config &= ~BYPASS;
>> +	/*
>> +	 * Disable direct mode as we don't DML to MASTER the AHB bus.
>> +	 * BAM connected with DML should MASTER the AHB bus.
>> +	 */
>> +	config &= ~DIRECT_MODE;
>> +	/*
>> +	 * Disable infinite mode transfer as we won't be doing any
>> +	 * infinite size data transfers. All data transfer will be
>> +	 * of finite data size.
>> +	 */
>> +	config &= ~INFINITE_CONS_TRANS;
>> +	writel_relaxed(config, base + DML_CONFIG);
>> +
>> +	/*
>> +	 * Initialize the logical BAM pipe size for producer
>> +	 * and consumer.
>> +	 */
>> +	writel_relaxed(PRODUCER_PIPE_LOGICAL_SIZE,
>> +		       base + DML_PRODUCER_PIPE_LOGICAL_SIZE);
>> +	writel_relaxed(CONSUMER_PIPE_LOGICAL_SIZE,
>> +		       base + DML_CONSUMER_PIPE_LOGICAL_SIZE);
>> +
>> +	/* Initialize Producer/consumer pipe id */
>> +	writel_relaxed(producer_id | (consumer_id << CONSUMER_PIPE_ID_SHFT),
>> +		       base + DML_PIPE_ID);
>> +
>
> We have an mb() here too. Not sure why though. There's lots of comments
> downstream but not where it actually would help!
I will add mb here and try to add some comments here.


>
>> +	return 0;
>> +}
>> diff --git a/drivers/mmc/host/mmci_qcom_dml.h b/drivers/mmc/host/mmci_qcom_dml.h
>> new file mode 100644
>> index 0000000..412e9a3
>> --- /dev/null
>> +++ b/drivers/mmc/host/mmci_qcom_dml.h
>> @@ -0,0 +1,31 @@
>> +/*
>> + *
>> + * Copyright (c) 2014, Code Aurora Forum. All rights reserved.
>
> Hmm I see:
>
> Copyright (c) 2011, The Linux Foundation. All rights reserved.
>
> in these files. Can you use that?
https://git.linaro.org/landing-teams/working/qualcomm/kernel.git/blob/refs/heads/inforce/ifc6410/v1.5:/drivers/mmc/host/msm_sdcc_dml.c
in 3.4 kernel has:

Copyright (c) 2011, Code Aurora Forum. All rights reserved.

Do you still want to add Linux Foundation copyright in it.

thanks,
srini
>
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