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Date: Tue, 13 Nov 2012 12:34:19 +0100 From: Thomas Petazzoni <thomas.petazzoni@...e-electrons.com> To: Francois Romieu <romieu@...zoreil.com> Cc: Eric Dumazet <eric.dumazet@...il.com>, "David S. Miller" <davem@...emloft.net>, Lennert Buytenhek <kernel@...tstofly.org>, netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, Jason Cooper <jason@...edaemon.net>, Andrew Lunn <andrew@...n.ch>, Gregory Clement <gregory.clement@...e-electrons.com>, Lior Amsalem <alior@...vell.com>, Maen Suleiman <maen@...vell.com> Subject: Re: [PATCH v4] Network driver for the Armada 370 and Armada XP ARM Marvell SoCs François, Thanks for your detailed review. I have a few comments/questions below on specific topics. On Sat, 3 Nov 2012 12:53:21 +0100, Francois Romieu wrote: > > + if (rxq->descs == NULL) { > > + netdev_err(pp->dev, > > + "rxQ=%d: Can't allocate %d bytes for %d RX descr\n", > > + rxq->id, rxq->size * MVNETA_DESC_ALIGNED_SIZE, > > + rxq->size); > > + return -ENOMEM; > > + } > > + > > + BUG_ON(rxq->descs != > > + PTR_ALIGN(rxq->descs, MVNETA_CPU_D_CACHE_LINE_SIZE)); > > There is no reason to crash. Well, there is a reason: the hardware will not work properly if rxq->descs is not aligned on a MVNETA_CPU_D_CACHE_LINE_SIZE boundary. So one solution is to over-allocated to guarantee the alignment, but since practically speaking MVNETA_CPU_D_CACHE_LINE_SIZE=32 and dma_alloc_coherent() returns things that seem at least 32 bytes aligned, it sounded overkill to include more code to fix a problem that doesn't exist. This BUG_ON() is here solely for the purpose of noisily letting the user know if this implicit assumption on the alignment of dma_alloc_coherent() allocated buffer changes in the future. I can turn this into an error if you prefer: if (rxq->descs != PTR_ALIGN(rxq->descs, MVNETA_CPU_D_CACHE_LINE_SIZE)) { netdev_err(pp->dev, "improper buffer alignement assumption, driver needs fixing\n"); dma_free_coherent(...); return -EINVAL; } > (...] > > +static int mvneta_txq_init(struct mvneta_port *pp, > > + struct mvneta_tx_queue *txq) > > +{ > > + txq->size = pp->tx_ring_size; > > + > > + /* Allocate memory for TX descriptors */ > > + txq->descs = dma_alloc_coherent(pp->dev->dev.parent, > > + txq->size * MVNETA_DESC_ALIGNED_SIZE, > > + &txq->descs_phys, > > + DMA_BIDIRECTIONAL); > > &txq->descs_phys, DMA_BIDIRECTIONAL); Aaah, thanks for pointing this one! It should have been GFP_KERNEL, not DMA_BIDIRECTIONAL here. > > + if (txq->descs == NULL) { > > + netdev_err(pp->dev, > > + "txQ=%d: Can't allocate %d bytes for %d TX descr\n", > > + txq->id, txq->size * MVNETA_DESC_ALIGNED_SIZE, > > + txq->size); > > + return -ENOMEM; > > + } > > + > > + /* Make sure descriptor address is cache line size aligned */ > > + BUG_ON(txq->descs != > > + PTR_ALIGN(txq->descs, MVNETA_CPU_D_CACHE_LINE_SIZE)); > > There is no reason to crash. Same as above :-) > [...] > > +static int mvneta_setup_rxqs(struct mvneta_port *pp) > > +{ > > + int queue; > > + > > + for (queue = 0; queue < rxq_number; queue++) { > > + int err = mvneta_rxq_init(pp, &pp->rxqs[queue]); > > + if (err) { > > + netdev_err(pp->dev, > > + "%s: can't create RxQ rxq=%d\n", > > netdev_err(pp->dev, "%s: can't create RxQ rxq=%d\n", > > > + __func__, queue); > > + mvneta_cleanup_rxqs(pp); > > + return -ENODEV; > > mvneta_rxq_init should return a proper error code and it should be > propagated (option: break instead of return and mvneta_setup_rxqs scoped > err variable) Besides turning the "return -ENODEV;" into "return err;", I don't see what is the other problem here? mvneta_rxq_init() properly returns -ENOMEM where there is a memory allocation failure, and mvneta_cleanup_rxqs() properly cleans up *all* initialized rxqs. Is there something I'm missing? Thanks again for your review! Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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