Hi, Thanks for the patch. On 18/05/2021 09:39, Stephan Gerhold wrote: > s3fwrn5 has a NFC_CLK_REQ output GPIO, which is asserted whenever > the clock is needed for the current operation. This GPIO can be either > connected directly to the clock provider, or must be monitored by > this driver. > > As an example for the first case, on many Qualcomm devices the > NFC clock is provided by the main PMIC. The clock can be either > permanently enabled (clocks = <&rpmcc RPM_SMD_BB_CLK2>) or enabled > only when requested through a special input pin on the PMIC > (clocks = <&rpmcc RPM_SMD_BB_CLK2_PIN>). > > On the Samsung Galaxy A3/A5 (2015, Qualcomm MSM8916) this mechanism > is used with S3FWRN5's NFC_CLK_REQ output GPIO to enable the clock > only when necessary. However, to make that work the s3fwrn5 driver > must keep the RPM_SMD_BB_CLK2_PIN clock enabled. This contradicts the code. You wrote that pin should be kept enabled (somehow... by driver? by it's firmware?) but your code requests the clock from provider. > > This commit adds support for this by requesting an optional clock Don't write "This commit". https://elixir.bootlin.com/linux/latest/source/Documentation/process/submitting-patches.rst#L89 > and keeping it permanently enabled. Note that the actual (physical) > clock won't be permanently enabled since this will depend on the > output of NFC_CLK_REQ from S3FWRN5. What pin is that "NFC_CLK_REQ"? I cannot find such name. Is it GPIO2? What clock are you talking here? The one going to the modem part? I also don't see here how this clock is going to be automatically on-off... driver does not perform such. Unless you speak about your particular HW configuration where the GPIO is somehow connected with AND (but then it is not relevant to the code). > > In the future (when needed by some other device) this could be > extended to work for the second case (monitoring the NFC_CLK_REQ > GPIO and enabling the clock from the kernel when needed). > > Signed-off-by: Stephan Gerhold <stephan@xxxxxxxxxxx> > --- > drivers/nfc/s3fwrn5/i2c.c | 32 ++++++++++++++++++++++++++++++-- > 1 file changed, 30 insertions(+), 2 deletions(-) > Best regards, Krzysztof
