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Message-ID: <20240222174501.4cbe03ab@bootlin.com>
Date: Thu, 22 Feb 2024 17:45:01 +0100
From: Herve Codina <herve.codina@...tlin.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Vadim Fedorenko <vadim.fedorenko@...ux.dev>, "David S. Miller"
<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Yury Norov
<yury.norov@...il.com>, Rasmus Villemoes <linux@...musvillemoes.dk>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, Andrew Lunn <andrew@...n.ch>, Mark Brown
<broonie@...nel.org>, Christophe Leroy <christophe.leroy@...roup.eu>,
Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v4 1/5] net: wan: Add support for QMC HDLC
On Thu, 22 Feb 2024 17:29:05 +0200
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> On Thu, Feb 22, 2024 at 03:22:14PM +0100, Herve Codina wrote:
> > The QMC HDLC driver provides support for HDLC using the QMC (QUICC
> > Multichannel Controller) to transfer the HDLC data.
>
> ...
>
> > +struct qmc_hdlc {
> > + struct device *dev;
> > + struct qmc_chan *qmc_chan;
> > + struct net_device *netdev;
> > + bool is_crc32;
> > + spinlock_t tx_lock; /* Protect tx descriptors */
>
> Just wondering if above tx/rx descriptors should be aligned on a cacheline
> for DMA?
These descriptors are not used by DMA.
Not sure that aligning them to a cacheline is really needed.
>
> > + struct qmc_hdlc_desc tx_descs[8];
> > + unsigned int tx_out;
> > + struct qmc_hdlc_desc rx_descs[4];
> > +};
>
> ...
>
> > +#define QMC_HDLC_RX_ERROR_FLAGS (QMC_RX_FLAG_HDLC_OVF | \
> > + QMC_RX_FLAG_HDLC_UNA | \
> > + QMC_RX_FLAG_HDLC_ABORT | \
> > + QMC_RX_FLAG_HDLC_CRC)
>
> Wouldn't be slightly better to have it as
>
> #define QMC_HDLC_RX_ERROR_FLAGS \
> (QMC_RX_FLAG_HDLC_OVF | QMC_RX_FLAG_HDLC_UNA | \
> QMC_RX_FLAG_HDLC_CRC | QMC_RX_FLAG_HDLC_ABORT)
>
> ?
Will be done in the next iteration.
>
> ...
>
> > + ret = qmc_chan_write_submit(qmc_hdlc->qmc_chan, desc->dma_addr, desc->dma_size,
> > + qmc_hdlc_xmit_complete, desc);
> > + if (ret) {
>
> > + dev_err(qmc_hdlc->dev, "qmc chan write returns %d\n", ret);
> > + dma_unmap_single(qmc_hdlc->dev, desc->dma_addr, desc->dma_size, DMA_TO_DEVICE);
> > + return ret;
>
> I would do other way around, i.e. release resource followed up by printing
> a message. Printing a message is a slow operation and may prevent the (soon
> freed) resources to be re-used earlier.
Will do that in the next iteration.
>
> > + }
>
> ...
>
> > + spin_lock_irqsave(&qmc_hdlc->tx_lock, flags);
>
> Why not using cleanup.h from day 1?
I don't know about cleanup.h.
Can you tell me more ?
How should I use it ?
>
> > +end:
>
> This label, in particular, will not be needed with above in place.
>
> > + spin_unlock_irqrestore(&qmc_hdlc->tx_lock, flags);
> > + return ret;
> > +}
>
> ...
>
> > + /* Queue as many recv descriptors as possible */
> > + for (i = 0; i < ARRAY_SIZE(qmc_hdlc->rx_descs); i++) {
> > + desc = &qmc_hdlc->rx_descs[i];
> > +
> > + desc->netdev = netdev;
> > + ret = qmc_hdlc_recv_queue(qmc_hdlc, desc, chan_param.hdlc.max_rx_buf_size);
>
> > + if (ret) {
> > + if (ret == -EBUSY && i != 0)
> > + break; /* We use all the QMC chan capability */
> > + goto free_desc;
> > + }
>
> Can be unfolded to
>
> if (ret == -EBUSY && i)
> break; /* We use all the QMC chan capability */
> if (ret)
> goto free_desc;
>
> Easy to read and understand.
Sure, will be changed.
>
> > + }
>
> ...
>
> > +static int qmc_hdlc_probe(struct platform_device *pdev)
> > +{
>
> With
>
> struct device *dev = &pdev->dev;
>
> the below code will be neater (see other comments for the examples).
Will use that.
>
> > + struct device_node *np = pdev->dev.of_node;
>
> It is used only once, drop it (see below).
Ok.
>
> > + struct qmc_hdlc *qmc_hdlc;
> > + struct qmc_chan_info info;
> > + hdlc_device *hdlc;
> > + int ret;
> > +
> > + qmc_hdlc = devm_kzalloc(&pdev->dev, sizeof(*qmc_hdlc), GFP_KERNEL);
> > + if (!qmc_hdlc)
> > + return -ENOMEM;
> > +
> > + qmc_hdlc->dev = &pdev->dev;
> > + spin_lock_init(&qmc_hdlc->tx_lock);
> > +
> > + qmc_hdlc->qmc_chan = devm_qmc_chan_get_bychild(qmc_hdlc->dev, np);
>
> qmc_hdlc->qmc_chan = devm_qmc_chan_get_bychild(dev, dev->of_node);
>
> > + if (IS_ERR(qmc_hdlc->qmc_chan)) {
> > + ret = PTR_ERR(qmc_hdlc->qmc_chan);
> > + return dev_err_probe(qmc_hdlc->dev, ret, "get QMC channel failed\n");
>
> return dev_err_probe(dev, PTR_ERR(qmc_hdlc->qmc_chan), "get QMC channel failed\n");
>
> > + }
> > +
> > + ret = qmc_chan_get_info(qmc_hdlc->qmc_chan, &info);
> > + if (ret) {
>
> > + dev_err(qmc_hdlc->dev, "get QMC channel info failed %d\n", ret);
> > + return ret;
>
> Why not using same message pattern everywhere, i.e. dev_err_probe()?
>
> return dev_err_probe(dev, ret, "get QMC channel info failed\n");
>
> (and so on...)
No reason. Just because I missed them.
Will be updated using dev_err_probe().
>
> > + }
> > +
> > + if (info.mode != QMC_HDLC) {
> > + dev_err(qmc_hdlc->dev, "QMC chan mode %d is not QMC_HDLC\n",
> > + info.mode);
> > + return -EINVAL;
> > + }
> > +
> > + qmc_hdlc->netdev = alloc_hdlcdev(qmc_hdlc);
> > + if (!qmc_hdlc->netdev) {
>
> > + dev_err(qmc_hdlc->dev, "failed to alloc hdlc dev\n");
> > + return -ENOMEM;
>
> We do not issue a message for -ENOMEM.
And I know :(
Will be updated.
>
> > + }
> > +
> > + hdlc = dev_to_hdlc(qmc_hdlc->netdev);
> > + hdlc->attach = qmc_hdlc_attach;
> > + hdlc->xmit = qmc_hdlc_xmit;
> > + SET_NETDEV_DEV(qmc_hdlc->netdev, qmc_hdlc->dev);
> > + qmc_hdlc->netdev->tx_queue_len = ARRAY_SIZE(qmc_hdlc->tx_descs);
> > + qmc_hdlc->netdev->netdev_ops = &qmc_hdlc_netdev_ops;
> > + ret = register_hdlc_device(qmc_hdlc->netdev);
> > + if (ret) {
> > + dev_err(qmc_hdlc->dev, "failed to register hdlc device (%d)\n", ret);
> > + goto free_netdev;
> > + }
> > +
> > + platform_set_drvdata(pdev, qmc_hdlc);
> > +
> > + return 0;
> > +
> > +free_netdev:
> > + free_netdev(qmc_hdlc->netdev);
> > + return ret;
> > +}
>
>
Thanks for the review.
Hervé
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