On Dec 13, 2010, at 6:50 AM, David Vrabel wrote: > Nicolas Pitre wrote: >> On Wed, 8 Dec 2010, zhangfei gao wrote: >> >>> On Tue, Dec 7, 2010 at 9:50 PM, Philip Rakity <prak...@marvell.com> wrote: >>>> On Dec 7, 2010, at 5:49 PM, zhangfei gao wrote: >>>>> 2. we have to fully verify the hardware clk gating internally before >>>>> sending the code. >>>> code tested under marvell 2.6.32 linux. >>> Thanks a lot, just wander could sdio be supported, since marvell8787 >>> requires around 10 clock cycles after cmd53 finished. > > The specification requires only 8 clocks after end bit of a CMD53 data > block. (SD physical spec 3.01 section 4.4, clock control). It is > possible that the controller sends more than the minimum. >
hardware was designed before sdio 3.0 >> SDIO is currently left out as this is not clear if all SDIO cards still >> can send interrupts if their clock is disabled, or even function >> properly. This might have to be a property that the SDIO function >> drivers could provide to the core. > > It's a minefield. > > Cards in 1-bit mode may interrupt at any time whether there is a clock > or not. > > Cards compliant to SDIO v2.00 should require the clock to generate > interrupts when in 4-bit mode as this is what's specified in the > specification. As a vendor-specific extension, some v2.00 cards (e.g., > all CSR devices) do not require the clock. > > Cards compliant to SDIO v3.00 may optionally have the clock turned off > if the card indicates support for asynchronous interrupts and support > has been enabled (via CCCR register bits). > > Some host controllers will not detect interrupts if the clock is off and > 4-bit mode is enabled. > > I would suggest: > > * Cards have a property: auto-clock-disable which indicates if the the > clock can be switched off automatically by mmc core or if hardware clock > gating may be used. > > a. Memory cards would set this to true. > b. SDIO v2.00 cards would set this to false. > c. SDIO v3.00 cards would set this to true if asynchronous interrupts > are supported and enabled, otherwise false. > d. combo cards set this based on the SDIO function. > > * If necessary, host controllers switch to 1-bit mode if the clock is > turned off and switch back to 4-bit mode when the clock is turned back > on (e.g., some sdhci controllers require this). > > * SDIO function drivers can set auto-clock-disable to true if they're > for a v2.00 card that supports asynchronous interrupts. > > David > -- > David Vrabel, Senior Software Engineer, Drivers > CSR, Churchill House, Cambridge Business Park, Tel: +44 (0)1223 692562 > Cowley Road, Cambridge, CB4 0WZ http://www.csr.com/ > > > Member of the CSR plc group of companies. CSR plc registered in England and > Wales, registered number 4187346, registered office Churchill House, > Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
