> -----Original Message----- > From: linux-mmc-ow...@vger.kernel.org [mailto:linux-mmc- > ow...@vger.kernel.org] On Behalf Of Adrian Hunter > Sent: Friday, December 09, 2011 6:03 PM > To: Huang Changming-R66093 > Cc: linux-mmc@vger.kernel.org; Huang Changming-R66093 > Subject: Re: [PATCH 2/4] MMC/SD: Add callback function to detect card > > On 05/12/11 11:23, r66...@freescale.com wrote: > > From: Jerry Huang <chang-ming.hu...@freescale.com> > > > > In order to check whether the card has been removed, the function > > mmc_send_status() will send command CMD13 to card and ask the card to > > send its status register to sdhc driver, which will generate many > > interrupts repeatedly and make the system performance bad. > > That should not be true. sdhci.c will not send a command to the card if > the card is not present i.e. see this excerpt from > sdhci_request(): > > > /* If polling, assume that the card is always present. */ > if (host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION) > present = true; > else > present = sdhci_readl(host, SDHCI_PRESENT_STATE) & > SDHCI_CARD_PRESENT; > > if (!present || host->flags & SDHCI_DEVICE_DEAD) { > host->mrq->cmd->error = -ENOMEDIUM; > tasklet_schedule(&host->finish_tasklet); > -- But, for some controller, this field of SDHCI_PRESENT_STATE register is reserved and always is 1. When the card is absent, many command will try to send to the card, and generate many interrupt. If even controller can detect the card state, if the card is absent as you said, this command can't send to card. But, when card is present, there will be many command to the card and many interrupts will be generated, that will affect the performance. So, I don't think this comment is not correct.
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