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Date: Thu, 17 Jan 2019 09:58:08 +0000
From: Laurentiu Tudor <laurentiu.tudor@....com>
To: Robin Murphy <robin.murphy@....com>,
"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
dl-linux-imx <linux-imx@....com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
"kernel@...gutronix.de" <kernel@...gutronix.de>,
"wsa@...-dreams.de" <wsa@...-dreams.de>
CC: "linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] i2c: imx: dma map the i2c data i/o register
Hi Robin,
On 16.01.2019 19:55, Robin Murphy wrote:
> On 16/01/2019 16:17, Laurentiu Tudor wrote:
>> This is an attempt to fix an iommu exception when doing dma to the
>> i2c controller with EDMA. Without these mappings the smmu raises a
>> context fault [1] exactly with the address of the i2c data i/o reg.
>> This was seen on an NXP LS1043A chip while working on enabling SMMU.
>
> Rather than gradually adding much the same code to potentially every
> possible client driver, can it not be implemented once in the edma
> driver as was done for pl330 and rcar-dmac? That also sidesteps any of
> the nastiness of smuggling a dma_addr_t via a phys_addr_t variable.
Thanks for the pointer. I was actually unsure where this should be
tackled: either i2c or dma side. Plus I somehow managed to completely
miss the support added in the dma drivers you mention. I'll start
looking into stealing some of your code [1]. :-)
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4d6d74e22096543cb3b35e717cf1b9aea3655f37
---
Best Regards, Laurentiu
>
>> [1] arm-smmu 9000000.iommu: Unhandled context fault: fsr=0x402,
>> iova=0x02180004, fsynr=0x150021, cb=7
>>
>> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
>> ---
>> drivers/i2c/busses/i2c-imx.c | 57 +++++++++++++++++++++++++++++-------
>> 1 file changed, 47 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
>> index 4e34b1572756..07cc8f4b45b9 100644
>> --- a/drivers/i2c/busses/i2c-imx.c
>> +++ b/drivers/i2c/busses/i2c-imx.c
>> @@ -202,6 +202,9 @@ struct imx_i2c_struct {
>> struct pinctrl_state *pinctrl_pins_gpio;
>> struct imx_i2c_dma *dma;
>> +
>> + dma_addr_t dma_tx_addr;
>> + dma_addr_t dma_rx_addr;
>> };
>> static const struct imx_i2c_hwdata imx1_i2c_hwdata = {
>> @@ -274,17 +277,20 @@ static inline unsigned char
>> imx_i2c_read_reg(struct imx_i2c_struct *i2c_imx,
>> /* Functions for DMA support */
>> static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
>> - dma_addr_t phy_addr)
>> + phys_addr_t phy_addr)
>> {
>> struct imx_i2c_dma *dma;
>> struct dma_slave_config dma_sconfig;
>> struct device *dev = &i2c_imx->adapter.dev;
>> int ret;
>> + phys_addr_t i2dr_pa;
>> dma = devm_kzalloc(dev, sizeof(*dma), GFP_KERNEL);
>> if (!dma)
>> return -ENOMEM;
>> + i2dr_pa = phy_addr + (IMX_I2C_I2DR << i2c_imx->hwdata->regshift);
>> +
>> dma->chan_tx = dma_request_chan(dev, "tx");
>> if (IS_ERR(dma->chan_tx)) {
>> ret = PTR_ERR(dma->chan_tx);
>> @@ -293,15 +299,25 @@ static int i2c_imx_dma_request(struct
>> imx_i2c_struct *i2c_imx,
>> goto fail_al;
>> }
>> - dma_sconfig.dst_addr = phy_addr +
>> - (IMX_I2C_I2DR << i2c_imx->hwdata->regshift);
>> + i2c_imx->dma_tx_addr = dma_map_resource(dma->chan_tx->device->dev,
>> + i2dr_pa,
>> + DMA_SLAVE_BUSWIDTH_1_BYTE,
>> + DMA_MEM_TO_DEV, 0);
>> + ret = dma_mapping_error(dma->chan_tx->device->dev,
>> + i2c_imx->dma_tx_addr);
>> + if (ret) {
>> + dev_err(dev, "can't dma map tx destination (%d)\n", ret);
>> + goto fail_tx;
>> + }
>> +
>> + dma_sconfig.dst_addr = i2c_imx->dma_tx_addr;
>> dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
>> dma_sconfig.dst_maxburst = 1;
>> dma_sconfig.direction = DMA_MEM_TO_DEV;
>> ret = dmaengine_slave_config(dma->chan_tx, &dma_sconfig);
>> if (ret < 0) {
>> dev_err(dev, "can't configure tx channel (%d)\n", ret);
>> - goto fail_tx;
>> + goto fail_tx_dma;
>> }
>> dma->chan_rx = dma_request_chan(dev, "rx");
>> @@ -309,18 +325,28 @@ static int i2c_imx_dma_request(struct
>> imx_i2c_struct *i2c_imx,
>> ret = PTR_ERR(dma->chan_rx);
>> if (ret != -ENODEV && ret != -EPROBE_DEFER)
>> dev_err(dev, "can't request DMA rx channel (%d)\n", ret);
>> - goto fail_tx;
>> + goto fail_tx_dma;
>> }
>> - dma_sconfig.src_addr = phy_addr +
>> - (IMX_I2C_I2DR << i2c_imx->hwdata->regshift);
>> + i2c_imx->dma_rx_addr = dma_map_resource(dma->chan_rx->device->dev,
>> + i2dr_pa,
>> + DMA_SLAVE_BUSWIDTH_1_BYTE,
>> + DMA_DEV_TO_MEM, 0);
>> + ret = dma_mapping_error(dma->chan_rx->device->dev,
>> + i2c_imx->dma_rx_addr);
>> + if (ret) {
>> + dev_err(dev, "can't dma map rx source (%d)\n", ret);
>> + goto fail_rx;
>> + }
>> +
>> + dma_sconfig.src_addr = i2c_imx->dma_rx_addr;
>> dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
>> dma_sconfig.src_maxburst = 1;
>> dma_sconfig.direction = DMA_DEV_TO_MEM;
>> ret = dmaengine_slave_config(dma->chan_rx, &dma_sconfig);
>> if (ret < 0) {
>> dev_err(dev, "can't configure rx channel (%d)\n", ret);
>> - goto fail_rx;
>> + goto fail_rx_dma;
>> }
>> i2c_imx->dma = dma;
>> @@ -330,8 +356,14 @@ static int i2c_imx_dma_request(struct
>> imx_i2c_struct *i2c_imx,
>> return 0;
>> +fail_rx_dma:
>> + dma_unmap_resource(dma->chan_rx->device->dev, i2c_imx->dma_rx_addr,
>> + DMA_SLAVE_BUSWIDTH_1_BYTE, DMA_DEV_TO_MEM, 0);
>> fail_rx:
>> dma_release_channel(dma->chan_rx);
>> +fail_tx_dma:
>> + dma_unmap_resource(dma->chan_tx->device->dev, i2c_imx->dma_tx_addr,
>> + DMA_SLAVE_BUSWIDTH_1_BYTE, DMA_MEM_TO_DEV, 0);
>> fail_tx:
>> dma_release_channel(dma->chan_tx);
>> fail_al:
>> @@ -1057,7 +1089,7 @@ static int i2c_imx_probe(struct platform_device
>> *pdev)
>> struct imxi2c_platform_data *pdata = dev_get_platdata(&pdev->dev);
>> void __iomem *base;
>> int irq, ret;
>> - dma_addr_t phy_addr;
>> + phys_addr_t phy_addr;
>> dev_dbg(&pdev->dev, "<%s>\n", __func__);
>> @@ -1072,7 +1104,7 @@ static int i2c_imx_probe(struct platform_device
>> *pdev)
>> if (IS_ERR(base))
>> return PTR_ERR(base);
>> - phy_addr = (dma_addr_t)res->start;
>> + phy_addr = res->start;
>> i2c_imx = devm_kzalloc(&pdev->dev, sizeof(*i2c_imx), GFP_KERNEL);
>> if (!i2c_imx)
>> return -ENOMEM;
>> @@ -1220,6 +1252,11 @@ static int i2c_imx_remove(struct
>> platform_device *pdev)
>> pm_runtime_put_noidle(&pdev->dev);
>> pm_runtime_disable(&pdev->dev);
>> + dma_unmap_resource(&pdev->dev, i2c_imx->dma_tx_addr,
>> + DMA_SLAVE_BUSWIDTH_1_BYTE, DMA_MEM_TO_DEV, 0);
>> + dma_unmap_resource(&pdev->dev, i2c_imx->dma_rx_addr,
>> + DMA_SLAVE_BUSWIDTH_1_BYTE, DMA_DEV_TO_MEM, 0);
>> +
>> return 0;
>> }
>>
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