On Thu, Mar 04, 2021 at 10:54:40AM +0800, Fangjian (Jay) wrote:
> On 2021/3/1 21:54, Mark Brown wrote:
> > On Mon, Mar 01, 2021 at 07:56:11PM +0800, Jay Fang wrote:
> > > +/* Disable IRQ bits */
> > > +static void hisi_spi_mask_intr(struct hisi_spi *hs, u32 mask)
> > > +{
> > > + u32 new_mask;
> > > +
> > > + new_mask = readl(hs->regs + HISI_SPI_IMR) | mask;
> > > + writel(new_mask, hs->regs + HISI_SPI_IMR);
> > > +}
> > This is a read/modify/write cycle and appears to be called from at least
> > process and interrupt context but I'm not seeing anything that stops two
> > different callers of it or the matching unmask function from running at
> > the same time.
> Those mask/unmask will not be called at the same time from process and
> interrupt context. In process context, unmask will be called after SPI
> controller be Disable and Flush (interrupt handing has ended).
Given that this is disabling the interrupt that doesn't sound like it's
going to be entirely robust - if we need to disable the interrupt
presumably there's some chance it might fire.
> > > + struct hisi_spi *hs = spi_controller_get_devdata(master);
> > > +
> > > + hs->n_bytes = hisi_spi_n_bytes(transfer);
> > > + hs->tx = (void *)transfer->tx_buf;
> > If there's a need to cast to void * something is very wrong here.
> Yes, fix compile warning.
This cast just masks whatever the problem is, if the compiler is
complaining about using a void pointer it's spotted an issue.
> > > + /* Ensure the data above is visible for all CPUs */
> > > + smp_mb();
> > This memory barrier seems worrying... are you *sure* this is the best
> > way to sync, and that the sync is best done here if it is needed rather
> > than after everything else is set up?
> The commit 0b6bfad ("spi: spi-dw: Remove extraneous locking") explains
> why memory barrier is needed here. And put it here to make it easier to
> understand.
The reader of this code won't have any kind of pointer to that commit,
this needs to be clearer.
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