At Thu, 21 Apr 2011 12:40:26 -0400,
Chris Ball wrote:
>
> Hi Takashi,
>
> On Thu, Apr 21 2011, Takashi Iwai wrote:
> > On HP laptops with JMicron 388 chip, the write-locked SD card isn't
> > detected correctly as read-only in many cases. This is because the
> > PRESENT_STATE register becomes unsable just after plugging, and it
> > returns the WRITE_PROTECT bit wrongly at the first read.
> >
> > This patch fixes the read-only detection by adding the own get_ro op
> > for checking the register more intensively with a relatively long
> > delay.
> >
> > The patch is tested with 2.6.39-rc4 kernel.
> >
> > Cc: Aries Lee <arieslee@xxxxxxxxxxx>
> > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> > ---
> > drivers/mmc/host/sdhci-pci.c | 34 ++++++++++++++++++++++++++++++++++
> > 1 files changed, 34 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-pci.c b/drivers/mmc/host/sdhci-pci.c
> > index a136be7..9037b2a 100644
> > --- a/drivers/mmc/host/sdhci-pci.c
> > +++ b/drivers/mmc/host/sdhci-pci.c
> > @@ -346,6 +346,35 @@ static void jmicron_enable_mmc(struct sdhci_host *host, int on)
> > writeb(scratch, host->ioaddr + 0xC0);
> > }
> >
> > +/* As PRESENT_STATE register becomes unstable just after plugging,
> > + * need to check the RO-cap multiple times with a relatively long delay.
> > + */
> > +
> > +#define SAMPLE_COUNT 5
> > +
> > +static unsigned int jmicron_get_ro(struct sdhci_host *host)
> > +{
> > + int i, ro_count;
> > +
> > + ro_count = 0;
> > + for (i = 0; i < SAMPLE_COUNT; i++) {
> > + int present = sdhci_readl(host, SDHCI_PRESENT_STATE);
> > + if (!(present & SDHCI_WRITE_PROTECT)) {
> > + if (++ro_count > SAMPLE_COUNT / 2)
> > + return 1;
> > + }
> > + msleep(30);
> > + }
> > + return 0;
> > +}
> > +
> > +static int sdhci_pci_enable_dma(struct sdhci_host *host);
> > +
> > +static struct sdhci_ops jmicron_pci_ops = {
> > + .enable_dma = sdhci_pci_enable_dma,
> > + .get_ro = jmicron_get_ro,
> > +};
> > +
> > static int jmicron_probe_slot(struct sdhci_pci_slot *slot)
> > {
> > if (slot->chip->pdev->revision == 0) {
> > @@ -383,6 +412,11 @@ static int jmicron_probe_slot(struct sdhci_pci_slot *slot)
> >
> > slot->host->mmc->caps |= MMC_CAP_BUS_WIDTH_TEST;
> >
> > + /* Replace the ops for unstable get_ro detection */
> > + if (slot->chip->pdev->device == PCI_DEVICE_ID_JMICRON_JMB388_SD ||
> > + slot->chip->pdev->device == PCI_DEVICE_ID_JMICRON_JMB388_ESD)
> > + slot->host->ops = &jmicron_pci_ops;
> > +
> > return 0;
> > }
>
> I don't like overwriting ops here -- it's too magical, and now we have
> to maintain the ops table in two places. A quirk seems justified here,
> even though we're trying to reduce them in general.
Well, I also used quirk bit in my very first version I worked for
2.6.32 kernel. But when I looked at 2.6.39, quirks are almost full --
only the last one bit is left for bit 31. So I didn't want to finish
it :)
> Can anyone find a better solution?
One way would be to copy the ops table itself in struct sdhci_host
instead of keeping the ops table pointer. Then you can overwrite only
the specific op in each probe_slot callback.
thanks,
Takashi
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