Re: [PATCH v2] HID: i2c-hid: Use block reads when possible to save power

From: Sultan Alsawaf <sultan@kerneltoast.com>
To: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Cc: aaron.ma@canonical.com, admin@kryma.net,
	andriy.shevchenko@linux.intel.com, benjamin.tissoires@redhat.com,
	hdegoede@redhat.com, hn.chen@weidahitech.com, jikos@kernel.org,
	kai.heng.feng@canonical.com, linux-i2c@vger.kernel.org,
	linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
	mika.westerberg@linux.intel.com, vicamo.yang@canonical.com,
	wsa@kernel.org
Subject: Re: [PATCH v2] HID: i2c-hid: Use block reads when possible to save power
Date: Wed, 1 Jul 2020 08:00:07 -0700	[thread overview]
Message-ID: <20200701150007.GA2141@sultan-book.localdomain> (raw)
In-Reply-To: <ef949533-c614-7afb-f206-5c54d827deac@linux.intel.com>

On Wed, Jul 01, 2020 at 11:04:01AM +0300, Jarkko Nikula wrote:
> On 6/29/20 8:43 PM, Sultan Alsawaf wrote:
> > Hmm, for some reason in 5.8 I get the same problem, but 5.7 is fine. Could you
> > try this on 5.7 and see if it works?
> > 
> > In the meantime I'll bisect 5.8 to see why it's causing problems for me...
> > 
> I see the same issue on top of v5.7:

Try reverting my "i2c: designware: Only check the first byte for SMBus block
read length" patch and apply the following change instead:

--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -394,10 +394,12 @@ i2c_dw_read(struct dw_i2c_dev *dev)
 			u32 flags = msgs[dev->msg_read_idx].flags;
 
 			*buf = dw_readl(dev, DW_IC_DATA_CMD);
-			/* Ensure length byte is a valid value */
-			if (flags & I2C_M_RECV_LEN &&
-				*buf <= I2C_SMBUS_BLOCK_MAX && *buf > 0) {
-				len = i2c_dw_recv_len(dev, *buf);
+			if (flags & I2C_M_RECV_LEN) {
+				/* Ensure length byte is a valid value */
+				if (*buf <= I2C_SMBUS_BLOCK_MAX && *buf > 0)
+					len = i2c_dw_recv_len(dev, *buf);
+				else
+					len = i2c_dw_recv_len(dev, len);
 			}
 			buf++;
 			dev->rx_outstanding--;
