linux-kernel - Re: [PATCH V2 1/3] i2c: busses: add SLIMpro I2C device driver on APM X-Gene platform

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Date:	Fri, 27 Mar 2015 16:30:54 -0700
From:	Feng Kan <fkan@....com>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	patches <patches@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-i2c@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, Hieu Le <hnle@....com>
Subject: Re: [PATCH V2 1/3] i2c: busses: add SLIMpro I2C device driver on APM
 X-Gene platform

On Mon, Mar 23, 2015 at 11:31 AM, Wolfram Sang <wsa@...-dreams.de> wrote:
> On Wed, Feb 18, 2015 at 11:34:01AM -0800, Feng Kan wrote:
>> Add SLIMpro I2C device driver on APM X-Gene platform. This I2C
>> device driver use the SLIMpro Mailbox driver to tunnel message to
>> the SLIMpro coprocessor to do the work of accessing I2C components.
>>
>> Signed-off-by: Feng Kan <fkan@....com>
>> Signed-off-by: Hieu Le <hnle@....com>
>
> Sigh, I lost my first review, so here we go again...
> It looks mostly good. Using checkpatch with '--strict' will show some
> whitespace issues. Please fix these.
>
>> +config I2C_XGENE_SLIMPRO
>> +     tristate "APM X-Gene SoC I2C SLIMpro devices support"
>> +     depends on ARCH_XGENE && MAILBOX
>
> COMPILE_TEST?
>
>> +static int start_i2c_msg_xfer(struct slimpro_i2c_dev *ctx)
>> +{
>> +     if (ctx->mbox_client.tx_block) {
>> +             if (!wait_for_completion_timeout(&ctx->rd_complete,
>> +                                              msecs_to_jiffies
>> +                                              (MAILBOX_OP_TIMEOUT)))
>
> Don't be too strict with the 80 char limit IMHO. I think it is more
> readable to combine the last two lines into one.
>
>> +     msg[0] = SLIMPRO_IIC_ENCODE_MSG(SLIMPRO_IIC_BUS, chip,
>> +                                     SLIMPRO_IIC_READ, protocol, addrlen,
>> +                                     readlen);
>
> ditto
>
>> +     msg[0] = SLIMPRO_IIC_ENCODE_MSG(SLIMPRO_IIC_BUS, chip,
>> +                                     SLIMPRO_IIC_WRITE, protocol, addrlen,
>> +                                     writelen);
>
> ditto
>
>> +     paddr = dma_map_single(ctx->dev, ctx->dma_buffer, readlen,
>> +                            DMA_FROM_DEVICE);
>
> The device should be the device of the dma channel.

The device is not visible on linux, DMA is done by the helper processor.
Perhaps you cah give me some idea how to do this. Thanks

>
>> +     paddr = dma_map_single(ctx->dev, ctx->dma_buffer, writelen,
>> +                            DMA_TO_DEVICE);
>
> ditto
>
>> +     rc = dma_mapping_error(ctx->dev, paddr);
>> +     if (dma_mapping_error(ctx->dev, paddr)) {
>
> if (rc)
>
>> +static struct i2c_algorithm xgene_slimpro_i2c_algorithm = {
>> +     .smbus_xfer = xgene_slimpro_i2c_xfer,
>
> Might be a tad less confusing to name this function
> xgene_slimpro_smbus_xfer. You decide.
>
>> +     rc = i2c_add_adapter(adapter);
>> +     if (rc) {
>> +             dev_err(&pdev->dev, "Adapter registeration failed\n");
>> +             return rc;
>> +     }
>> +
>> +     rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
>> +     if (rc)
>> +             dev_warn(&pdev->dev, "Unable to set dma mask\n");
>
> Shouldn't that be before i2c_add_adapter?
>
>> +static struct platform_driver xgene_slimpro_i2c_driver = {
>> +     .probe  = xgene_slimpro_i2c_probe,
>> +     .remove = xgene_slimpro_i2c_remove,
>> +     .driver = {
>> +             .name   = "xgene-slimpro-i2c",
>> +             .of_match_table = of_match_ptr(xgene_slimpro_i2c_id)
>
> You are DT only, do we need of_match_ptr?
>
>> +MODULE_DESCRIPTION("APM X-Gene SLIMpro I2C driver");
>> +MODULE_LICENSE("GPL");
>
> MODULE_AUTHOR left out intentionally?
>
> Thanks,
>
>    Wolfram
>
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