Hi,
Wolfram Sang wrote:
> I finally found some time.
Greatly appreciated.
> > Some SD host controllers (noticed on an integrated JMicron SD reader
> > on an HP Pavilion dv5-1250eo laptop) don't update the dma address
> > register before signaling a dma interrupt due to a dma boundary.
> > Detect this and update the register to the next 512KB boundary,
> > at which the transfer presumably stopped.
> >
> > As long as each transfer is at most 512KB in size (on this hardware
> > the max seems to be 65536 bytes), this fix is needed at most once
> > per transfer.
>
> But we can't guarantee that. Transfer could be up to 65535 * 2K.
In sdhci.c function sdhci_prepare_data there are these checks:
/* Sanity checks */
BUG_ON(data->blksz * data->blocks > 524288);
BUG_ON(data->blksz > host->mmc->max_blk_size);
BUG_ON(data->blocks > 65535);
I thought the first BUG_ON makes sure that the transfer doesn't go too big.
Then again, I might be missing something. Is 524288 not in bytes?
>
> > Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=28462
> >
> > Signed-off-by: Mikko Vinni <mmvinni <at> yahoo.com>
>
> Proper EMail please.
Hm, @gmail.com? (cc added for further emails)
> > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > index a25db42..8651731 100644
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -1537,9 +1537,27 @@ static void sdhci_data_irq(struct sdhci_host *host,
>u32 intmask)
> > * boundaries, but as we can't disable the feature
> > * we need to at least restart the transfer.
> > */
> > - if (intmask & SDHCI_INT_DMA_END)
> > - sdhci_writel(host, sdhci_readl(host, SDHCI_DMA_ADDRESS),
> > - SDHCI_DMA_ADDRESS);
> > + if (intmask & SDHCI_INT_DMA_END) {
> > + u32 dmastart, dmanow;
> > + dmastart = sg_dma_address(host->data->sg);
>
> This will only work for the first 512K, right?
True. If a transfer can cross more than one boundary, I suppose an
additional variable is needed to keep track of the current state.
>
> > + dmanow = sdhci_readl(host, SDHCI_DMA_ADDRESS);
> > + if (dmanow == dmastart) {
> > + /*
> > + * HW failed to increase the address.
> > + * Update to the next 512KB block boundary.
> > + */
> > + dmanow = (dmanow & ~0x7ffff) + 0x80000;
>
> Hmm, hardcoding these values is probably not a good idea. They should be
> dependent on what is written to MAKE_BLKSIZE. Maybe a common define?
Sorry, implementing that goes beyond my comfort zone. I would be happy to
test patches, though.
>
> > + if (dmanow > dmastart + host->data->blksz *
> > + host->data->blocks) {
> > + WARN_ON(1);
> > + dmanow = dmastart;
> > + }
>
> Did this happen?
No, but I though it brings some protection in case somebody *does*
change the boundary value without checking the code first (and happens
to be running on flawed hardware).
>
> > + DBG("%s: next DMA address forced "
> > + "from 0x%08x to 0x%08x\n",
> > + mmc_hostname(host->mmc), dmastart, dmanow);
> > + }
> > + sdhci_writel(host, dmanow, SDHCI_DMA_ADDRESS);
> > + }
> >
> > if (intmask & SDHCI_INT_DATA_END) {
> > if (host->cmd) {
> > --
> > 1.7.4.1
>
> Regards,
>
> Wolfram
>
Thanks
Mikko
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